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WO2019028054A1 - Additif de base de lewis bifonctionnel pour une homogénéité microscopique dans des cellules solaires de pérovskite - Google Patents

Additif de base de lewis bifonctionnel pour une homogénéité microscopique dans des cellules solaires de pérovskite Download PDF

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WO2019028054A1
WO2019028054A1 PCT/US2018/044658 US2018044658W WO2019028054A1 WO 2019028054 A1 WO2019028054 A1 WO 2019028054A1 US 2018044658 W US2018044658 W US 2018044658W WO 2019028054 A1 WO2019028054 A1 WO 2019028054A1
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perovskite
urea
lewis base
present disclosure
precursor composition
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Yang Yang
Jin-Wook Lee
Tae-Hee Han
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University of California Berkeley
University of California San Diego UCSD
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University of California Berkeley
University of California San Diego UCSD
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/50—Organic perovskites; Hybrid organic-inorganic perovskites [HOIP], e.g. CH3NH3PbI3
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
    • H10K30/50—Photovoltaic [PV] devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • Some embodiments of the present invention relate to perovskite solar cells, and more particularly to precursor materials for producing perovskite solar cells as well as the perovskite solar cells and methods of production using the precursor solution.
  • PVSK organo-lead halide perovskite
  • defects at grain boundaries induce shallow trap states, localizing charge carriers that are ultimately lost through non- radiative recombination, while the defect density across the grain interior is found to be dependent on the crystal facet, resulting in facet-dependent photovoltaic performance within a single grain.
  • several methods to control the crystal growth or passivation of defects have been previously developed while their effect on microscopic optoelectronic properties has not been fully understood.
  • An aspect of the present disclosure is to provide a precursor composition for producing a perovskite active layer of a photovoltaic device.
  • the composition includes a first component comprising a plurality of first molecules of a perovskite structure to be formed by an adduct combination; a second component comprising a plurality of second molecules of the perovskite structure to be formed by the adduct combination; and a nonvolatile Lewis base.
  • the nonvolatile base is nonvolatile above a first temperature and below a second temperature, the second temperature being greater than the first temperature.
  • the first temperature is approximately 70 deg. C and the second temperature is approximately 130 deg. C.
  • the plurality of first molecules are at least one of CH3 H3I, CH 3 H 3 Br, CH 3 H 3 C1, HC( H 2 ) 2 I, HC(NH 2 ) 2 Br, or HC( H 2 )2C1 molecules and the plurality of second molecules are at least one of Pbl 2 , PbBr 2 or PbCl 2 molecules.
  • the nonvolatile Lewis base is at least one of urea, thiourea, thioacetamide, acetamide, ethylene carbonate, propylene carbonate, or poly propylene carbonate.
  • the composition further includes a volatile Lewis base that is volatile above the first temperature.
  • the volatile Lewis base is at least one of dimethyl sulfoxide (DMSO), or N-Methyl-2-pyrrolidone ( MP).
  • the volatile Lewis base is dimethyl sulfoxide (DMSO), and the nonvolatile Lewis base is urea.
  • the nonvolatile Lewis base is selected so as to precipitate at perovskite grain boundary of the perovskite active layer to passivate defects at the perovskite grain boundary.
  • the nonvolatile Lewis base comprises a polymeric Lewis base.
  • repeating units in the polymeric Lewis base have a dipole moment greater than 5D.
  • repeating units in the polymeric Lewis base are at least one of ethylene carbonate (C3H4O3) or propylene carbonate (C4H6O3).
  • the polymeric Lewis base is selected so as to enable cross-linking between the polymeric Lewis base and perovskite grains in the perovskite structure.
  • the composition comprises a volatile Lewis base that is volatile above the first temperature.
  • the volatile Lewis base is at least one of dimethyl sulfoxide (DMSO), or N,N- Dimethylmethanamide (DMF).
  • Another aspect of the present disclosure is to provide a method of producing a photovoltaic device.
  • the method includes depositing a layer of the above precursor;
  • a further aspect of the present disclosure is providing a photovoltaic device.
  • the photovoltaic device is produced according to the above method.
  • FIGS. 1 A and IB are atomic force microscopic (AFM) images in of a cross- sectional MAPbI 3 layer, (A) for a bare MAPbI 3 and (B) MAPbI 3 with 4 mol% urea on Sn0 2 coated ITO substrates, respectively, according to embodiments of the present disclosure;
  • AFM atomic force microscopic
  • FIGS. 1C and ID depict cross-sectional scanning electron microscopic (SEM) images of the perovskite solar cell based on MAPbI 3 with and without 4 mol% urea are demonstrated, respectively, according to embodiments of the present disclosure
  • FIG. 2A shows photovoltaic parameters of MAPbI 3 perovskite solar cells as a function of urea amount: short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE), according to an embodiment of the present disclosure;
  • FIG. 2B shows current density-voltage (J-V) curves, according to an embodiment of the present disclosure
  • FIG. 2C shows external quantum efficiency (EQE) spectra of best performing device with and without 4 mol% urea, according to an embodiment of the present disclosure
  • FIG. 3 A is a schematics showing formation of perovskite layer with and without urea, according to an embodiment of the present disclosure
  • FIG. 3B shows photos of the films without (upper) and with 1 mmol of urea (lower) as a function of heat treatment temperature and time, according to embodiments of the present disclosure
  • FIG. 3C shows Fourier transform infrared (FT-IR) spectra of MAI-PblrDMSO adduct, urea, MAI-PblrDMSOurea and MAI-Pblrurea adduct powder, according to an embodiment of the present disclosure
  • FIG. 4A shows a Fourier transform infrared (FT-IR) spectra of urea (powder), MAPbI 3 (film) and MAPbI 3 with 4 mol% urea (film), according to an embodiment of the present disclosure
  • FIGS. 4C and 4D show x-ray diffraction patterns of the bare MAPbI 3 film and with urea, according to embodiments of the present disclosure
  • FIG. 5 A shows atomic force microscopic images (AFM) of bare MAPbI 3 , according to an embodiment of the present disclosure
  • FIG. 5B shows atomic force microscopic images (AFM) of MAPbI 3 with 4 mol% urea on Sn0 2 coated ITO substrates, according to an embodiment of the present disclosure
  • FIG. 5C is a cross sectional scanning electron microscopic (SEM) image of perovskite solar cells based on bare MAPbI 3 , according to an embodiment of the present disclosure
  • FIG. 5D is a cross sectional scanning electron microscopic (SEM) image of perovskite solar cells based on MAPbI 3 with 4 mol% urea, according to an embodiment of the present disclosure
  • FIG. 6 A shows UV-Vis and photoluminescence (PL) of the MAPbI 3 perovskite films measured to evaluate the effect of added urea on absorption and charge carrier properties of the film, according to an embodiment of the present disclosure
  • FIG. 6B shows the PL intensity versus wavelength indicating the steady-state, according to an embodiment of the present disclosure
  • FIG. 6C shows time resolved PL decay profiles of the MAPbI 3 films monitored at the peak emission (770 nm) to find the origin of the enhanced PL intensity, according to an embodiment of the present disclosure
  • FIG. 6D shows the decrease in defect density with addition of urea can be attributed to increased grain size due to slower crystallization with higher activation energy during the crystallization, resulting in decreased grain boundaries and their associated defects, according to an embodiment of the present disclosure
  • FIG. 7 A shows the Vm and W measured using Mott-Schottky plot in which the measured VbiS were 1.05 V and 1.17 V for the devices without and with urea respectively, correlating with enhanced Voc with urea, according to an embodiment of the present disclosure
  • FIG. 7B shows the calculated ⁇ from frequency dependent capacitance spectra shown in FIG. 7A, according to an embodiment of the present disclosure
  • FIG. 7C is a scanning electron microscopic (SEM) image of MAPbI 3 film with 50 mol% urea, according to an embodiment of the present disclosure
  • FIGS. 7D-7H show elemental distribution mapping images of the MAPbI 3 film, according to embodiments of the present disclosure
  • FIGS. 8A and 8B show the distribution of the measured current signal between the tip and perovskite film, which is overlaid on the topological images (gray scale), according to an embodiment of the present disclosure
  • FIG. 8C shows the trajectory of the scan of the height and current signal, in which the measured current varied significantly along the trajectory, according to an embodiment of the present disclosure
  • FIG. 8D shows the current signal along the trajectory, with addition of urea, according to an embodiment of the present disclosure
  • FIG. 8E shows the probability distribution of the measured current from the MAPbI 3 films with and without urea, respectively, according to an embodiment of the present disclosure
  • FIG. 9 shows thermogravimetric analysis (TGA) of urea (powder) where TGA was measured under dry air with heating rate of 10 °C/min, according to an embodiment of the present disclosure
  • FIG. 10 shows the adducts and urea powders used for FT-IR measurement, (A) MAI-PblrDMSO adduct, (B) urea, (C) MAI-PblrDMSOurea, and (D) MAI-Pblrurea adducts;
  • FIG. 11 depicts a steady-state PCE of perovskite solar cell without and with 4 mol% of urea, according to an embodiment of the present disclosure
  • FIGS. 12A and 12B shows current density-voltage (J-V) curves of perovskite solar cells based on (A) bare MAPbI 3 and (B) MAPbI 3 with 4 mol% urea measured with different scan direction with scan rate of 0.1 V/s, according to embodiments of the present disclosure;
  • FIGS. 13A and 13B show X-ray diffraction patterns of urea (powder) and perovskite film without and with 10 mol% and 20 mol% urea, respectively, according to embodiments of the present disclosure
  • FIGS. 14A-14F show scanning electron microscopic images (SEM) of
  • CH 3 H 3 PbI 3 perovskite solar cell (A, B, C) without and with (D, E, F) 4 mol% of urea, according to an embodiment of the present disclosure
  • FIG. 15 shows 1 -transmittance curves of MAPbI 3 film without and with 4 mol% urea, in which open circles are measured data and solid lines are linear fit of the data.
  • Inset shows magnified absorption onset region, related to FIGS. 6A-6D;
  • FIGS. 16A and 16B depict time resolved photoluminescence decay profiles of MAPbI 3 films (A) without and (B) with 4 mol% of urea, according to embodiments of the present disclosure
  • FIG. 17 depicts absorption spectra of MAPbI 3 film without and with 4 mol% urea, according to an embodiment of the present disclosure
  • FIG. 18A shows photovoltaic parameters of MAPbI 3 perovskite solar cells with different concentration of urea solution used for post-treatment for short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE), according to embodiments of the present disclosure
  • FIG. 18B shows photovoltaic parameters steady-state PCE, according to an embodiment of the present disclosure
  • FIG. 18C shows external quantum efficiency (EQE) spectra of best performing device without spin-coating of 27 mM urea solution, according to an embodiment of the present disclosure
  • FIGS. 19A and 19B are schematics showing (A) bare MAPbI 3 and (B) MAPbI 3 film with post-treatment of urea, according to embodiments of the present disclosure
  • FIGS. 19C and 19D show steady-state and time resolved photoluminescence (PL) decay profiles of the film with and without urea post-treatment, respectively, measured to investigate the origin of the improved photovoltaic performance, according to embodiments of the present disclosure
  • FIG. 20 shows a comparison of photovoltaic parameters of perovskite solar cells based on bare MAPbI 3 , MAPbI 3 film with spin-coating of 27 mM urea solution and MAPbI 3 film prepared with addition of 4 mol% urea, short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE), according to embodiments of the present disclosure;
  • FIGS. 21A and 21B show scanning electron microscopic (SEM) images of MAPbI 3 film with 50 mol% urea, according to an embodiment of the present disclosure
  • FIGS. 22 A and 22C are topological atomic force microscopy (c-AFM) images, according to embodiments of the present disclosure.
  • FIGS. 22B and 22D are conductivity images of bare ITO glass and with spin coating of 108 mM urea solution in 2-propanol, according to embodiments of the present disclosure;
  • FIGS. 23A and 23B depict, respectively, ex-situ and in-situ stability test of MAPbI 3 perovskite solar cell without and with 4 mol% urea, according to embodiments of the present disclosures;
  • FIGS. 24A-24B show absorption spectra measured after exposure to one sun illumination for different time, (A) bare MAPbI 3 film and (B) MAPbI 3 with 4 mol% urea, according to embodiments of the present disclosure; [0060] FIG. 24C depicts the evolution of absorbance at 600 nm as a function of light exposure time, according to an embodiment of the present disclosure;
  • FIG. 25 A is a schematic representation of Perovskite grain growth induced by a conventional small molecular intermediate phase, according to an embodiment of the present disclosure
  • FIG. 25B is a schematic representation of Perovskite grain growth induced by macromolecular intermediate phase, according to another embodiment of the present disclosure.
  • FIG. 25C is a schematic representation of process steps for the fabrication of a macromolecular intermediate phase-mediated growth of the perovskite film, according to an embodiment of the present disclosure
  • FIGS. 26A-D depict Fourier transform infrared (FTIR) spectra of synthesized adduct powders of CH3 H3I and Pbl 2 without and with the addition of Lewis bases (DMSO, EC, PC, and PPC), according to an embodiment of the present disclosure;
  • FTIR Fourier transform infrared
  • FIGS. 26E-26H show X-ray diffraction spectra of synthesized
  • FIG. 27A is a scanning electron microscopy image of CH 3 NH 3 PbI 3 film, according to an embodiment of the present disclosure
  • FIG. 27B is a scanning electron microscopy image of CFL FLPbL-PPC film, according to an embodiment of the present disclosure
  • FIG. 27C is a transmission electron microscopy (TEM) of cross-linked perovskite grains at lower magnification, according to an embodiment of the present disclosure
  • FIG. 27D is a transmission electron microscopy (TEM) of perovskite-polymer composite cross-linker between adjacent grains (highlighted region in FIG. 27C), according to an embodiment of the present disclosure
  • FIG. 27E is an Inverse Fast Fourier transform (IFFT) image of the region highlighted in FIG. 27C;
  • FIG. 27F is an enlargement of region (2) in the image shown in FIG. 27D showing the interface or bridge between the polymer and the perovskite;
  • FIG. 27G is a schematic diagram of various stages of a process for producing cross-linking between perovskite crystals using the polymer, according to an embodiment of the present disclosure
  • FIG. 28A depicts Reflective Fourier transform infrared (FTIR) spectra of the perovskite films without and with various types of Lewis bases (EC, PC, and PPC), according to embodiments of the present disclosure.
  • FTIR Reflective Fourier transform infrared
  • FIG. 28C shows most favorable Pb 2+ perovskite surface adsorption configurations of the Lewis bases and their calculated binding energies, according to embodiments of the present disclosure
  • FIG. 28D shows photoluminescence (PL) spectra (inset: normalized PL spectra) of perovskite films without and with Lewis bases, according to embodiments of the present disclosure
  • FIG. 28E shows time-resolved PL spectra of perovskite films without and with Lewis bases (Inset: PL lifetimes fitted from the time-resolved PL spectra), according to embodiments of the present disclosure
  • FIGS. 29A-29D show atomic force microscopy images of the obtained perovskite- polymer, according to an embodiment of the present disclosure
  • FIG. 30A shows X-ray diffraction spectra of bare CH 3 H 3 PbI 3 and
  • FIG. 3 OB shows X-ray diffraction spectra of bare CH 3 H 3 PbI 3 and CH 3 H 3 PbI 3 PPC (0.3 and 5.0 wt%) films against light (1.5 AM), according to an embodiment of the present disclosure
  • FIG. 30C shows X-ray diffraction spectra of bare CH 3 H 3 PbI 3 and
  • FIG. 30D shows photovoltaic parameters of CH 3 H 3 PbI 3 perovskite solar cells with the addition of different Lewis bases: short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE), according to an embodiment of the present disclosure; and
  • FIG. 30E shows a current density-voltage (J-V) characteristics of bare
  • An embodiment of the current invention is directed to a precursor composition for producing a perovskite active layer of a photovoltaic device that includes a first component that includes a plurality of first molecules of a perovskite structure to be formed by an adduct combination, a second component that includes a plurality of second molecules of the perovskite structure to be formed by the adduct combination, a first additive that includes a volatile Lewis base, and a second additive that includes a nonvolatile Lewis base.
  • the volatile Lewis base is volatile above a first temperature
  • the nonvolatile base is nonvolatile above the first temperature and below a second temperature, the second temperature being greater than the first temperature.
  • the volatile Lewis base can be at least one of dimethyl sulfoxide, or N-Methyl-2-pyrrolidone; and the nonvolatile Lewis base can be at least one of urea, thiourea, thioacetamide, acetamide, ethylene carbonate, propylene carbonate, or poly propylene carbonate.
  • the volatile Lewis base is dimethyl sulfoxide and the nonvolatile Lewis base is urea.
  • the plurality of first molecules are at least one of CH3 H3I, CH 3 H 3 Br, CH 3 H 3 C1, HC( H 2 ) 2 I, HC( H 2 ) 2 Br, or HC( H 2 ) 2 C1 molecules and the plurality of second molecules are at least one of Pbl 2 , PbBr 2 or PbCl 2 molecules.
  • An embodiment of the current invention is directed to a method of producing a photovoltaic device that includes depositing a layer of the precursor composition of an embodiment of the current invention onto a substructure, annealing the layer for a first time period below the first temperature, and after the said annealing, further annealing the layer for a second time period below the second temperature and above the first temperature.
  • An embodiment of the current invention is directed to a photovoltaic device produced according to a method of the current invention.
  • an embodiment of the current invention is directed to a method to fabricate highly efficient perovskite solar cell with Lewis base additives.
  • the Lewis base additives include urea, thiourea, thioacetamide, acetamide, ethylene carbonate, propylene carbonate, and/or poly propylene carbonate.
  • a urea additive here we describe the use of a urea additive.
  • methods and compositions for producing a perovskite active layer of a photovoltaic device are described in further detail.
  • ITO Indium doped tin oxide
  • Sn0 2 precursor solution 30 mM SnCl 2 -2H 2 0 (98%, Sigma- Adrich) in ethanol (anhydrous, Decon Laboratories Inc.) solution was stirred for an hour, which was filtered by 0.2 ⁇ syringe filter before use.
  • Sn0 2 layer was formed by spin-coating the precursor solution at 3000 rpm for 30 seconds two times.
  • DMF N,N-dimethylformamide
  • the solution was filtered by 0.2 ⁇ syringe filter before use.
  • Sn0 2 coated substrate was treated with UV-ozone for 15 min before spin-coating the perovskite solution.
  • the perovskite solution was spin-coated at 4000 rpm for 25 s, to which 0.3 mL of diethyl ether (anhydrous, >99.0%, contains BHT as stabilizer, Sigma- Aldrich) was dropped.
  • the resulting transparent adduct film was converted to perovskite by heat-treatment at 65 °C for 1 min followed by 100 °C for 30 min.
  • the spiro-MeOTAD solution was prepared by dissolving 85.8 mg of spiro-MeOTAD (Lumtech) in 1 mL of chlorobenzene (anhydrous, 99.8%, Sigma-Aldrich) in which 33.8 ⁇ of 4-tert-butylpyridine (96%, Aldrich) and 19.3 ⁇ of Li-TFSI (99.95%, Adrich, 520 mg/mL in acetonitrile) solution were added.
  • the spiro-MeOTAD solution was spin-coated at 3000 rpm for 20 s by dropping 17 ⁇ of the solution on spinning substrate.
  • 80 nm-thick silver was thermally evaporated at 0.5 A/s to be used as an electrode.
  • FIGS. 1 A and IB are atomic force microscopic (AFM) images in of a cross-sectional MAPbI 3 layer, (A) for a bare MAPbI 3 and (B) MAPbI 3 with 4 mol% urea on Sn0 2 coated ITO substrates, respectively, according to embodiments of the present disclosure.
  • the constitutive grains are significantly enlarged from about 200 nm to larger than 1 ⁇ .
  • FIGS. 1 A and IB are atomic force microscopic (AFM) images in of a cross-sectional MAPbI 3 layer, (A) for a bare MAPbI 3 and (B) MAPbI 3 with 4 mol% urea on Sn0 2 coated ITO substrates, respectively, according to embodiments of the present disclosure.
  • the constitutive grains are significantly enlarged from about 200 nm to larger than 1 ⁇ .
  • FIG. 1C and ID depict cross-sectional scanning electron microscopic (SEM) images of the perovskite solar cell based on MAPbI 3 with and without 4 mol% urea are demonstrated, respectively, according to embodiments of the present disclosure. While the thickness of the MAPbI 3 layer is measured to be around 580 nm regardless of addition of urea, the perovskite film with urea addition displayed single interfaces of large grains along the direction perpendicular to the substrate, whereas the bare MAPbI 3 film shows multiple interfaces between several smaller grains.
  • SEM scanning electron microscopic
  • FIG. 2A shows Photovoltaic parameters of MAPbI 3 perovskite solar cells as a function of urea amount: short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE), according to an embodiment of the present disclosure.
  • the amount of urea was varied from 0 mol% (without urea) to 6 mol% (0.06 mmol) with respect to MAI and Pbl 2 (1 mmol). As the urea amount is increased from 0 (reference) to 4 mol%, open circuit voltage (Voc) and fill factor (FF) are systematically enhanced.
  • FIG. 2B shows current density-voltage (J-V) curves, according to an embodiment of the present disclosure.
  • the current density and voltage (J-V) curves of the best performing devices are seen in FIG. 2B.
  • a PCE of 18.55% was achieved with addition of 4 mol% urea while 17.34%) was achievable without urea.
  • FIG. 2C shows external quantum efficiency (EQE) spectra of best performing device with and without 4 mol%> urea, according to an embodiment of the present disclosure.
  • the enhanced PCE was partially ascribed to a slight enhancement in Jsc, which was confirmed from the external quantum efficiency (EQE) spectra.
  • the integrated Jsc was calculated to be 20.91 mA/cm 2 for the reference and 21.26 mA/cm 2 with 4 mol% urea, which is well matched with the Jsc measured from J-V curve.
  • FIG. 11 depicts a steady-state PCE of perovskite solar cell without and with 4 mol%> of urea.
  • the PCE was calculated from current density and bias voltage (0.88 V for reference and 0.90 V for 4 mol%> urea sample), according to an embodiment.
  • J-V hysteresis with different scan direction was decreased after addition of urea.
  • the hysteresis index (HI) was decreased from 0.29 to 0.10 upon addition of 4 mol% urea (FIGS. 12A and 12B and Tablel).
  • J-V current density-voltage
  • Table 1 lists photovoltaic parameters and hysteresis index (HI) of perovskite solar cells based on bare MAPbI 3 and MAPbI 3 with 4 mol% urea measured with different scan direction with scan rate of 0.1 V/s.
  • perovskite solar cells have reached as high as 22.1%, making perovskite solar cells as a new class of photovoltaics to replace the prevailing silicon solar cell.
  • the superior optoelectronic properties of perovskite materials were found to be comparable to those of GaAs (absorption coefficient, Urbach tail energy, photon recycling process, hot carrier lifetime).
  • Such unprecedented optoelectronic properties have resulted in a calculated maximum achievable PCE of 31% that is close to the Shockley- Queisser limit.
  • Recent studies utilizing microscale spatially resolved spectroscopy have uncovered clues for further enhancement.
  • perovskite film Although the macroscopic properties of the perovskite film have been investigated to be superior to other type of the materials, there still exists heterogeneity at the microscale, where some areas of the film on a nano-to-micro scale show good optoelectronic properties while others show poor optoelectronic properties. Such areas with poor optoelectronic properties will degrade the overall photovoltaic performance.
  • the origin of the heterogeneity in perovskite film was suggested to be a structural disorder at i) grain boundaries and ii) grain interiors.
  • the Lewis base urea is found to interact with solution precursors to retard the crystal growth and enhance crystallinity, which subsequently precipitates at grain boundaries to passivate defects after completion of the crystal growth.
  • Resulting perovskite films show superior homogeneity in conductivity at both grain interior and boundaries compared to the bare perovskite films.
  • MAPbL CH 3 NH 3 PbI 3
  • the MAPbL perovskite layer was formed by the Lewis-base adduct approach while a non-volatile Lewis base urea was added to assist the grain growth and boundary passivation. Crystal growth and molecular interactions were monitored by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR).
  • XRD X-ray diffraction
  • FT-IR Fourier transform infrared spectroscopy
  • PL photoluminescence
  • c-AFM Conducting atomic force microscopy
  • the nonvolatile Lewis base additive was found to be advantageous for both crystal growth and defect passivation to reduce the heterogeneity in optoelectronic properties, resulting in an improved steady-state PCE from 16.80% to 18. 25% for MAPbL perovskite solar cells.
  • FIG. 3 A is a schematics showing formation of perovskite layer with and without urea, according to an embodiment of the present disclosure.
  • the MAPbL perovskite layer was prepared by the adduct approach, in which urea was added to the perovskite precursor solution. While dimethyl sulfoxide (DMSO) was found to be volatile at around 70 °C, urea was confirmed to be non-volatile at temperatures ⁇ 130 °C from thermogravimetric analysis (TGA).
  • TGA thermogravimetric analysis
  • FIG. 9 shows thermogravimetric analysis (TGA) of urea (powder) where TGA was measured under dry air with heating rate of 10 °C/min, according to an embodiment of the present disclosure.
  • TGA thermogravimetric analysis
  • FIG. 10 shows photos of the films without (upper) and with 1 mmol of urea (lower) as a function of heat treatment temperature and time, according to embodiments of the present disclosure.
  • the adduct film formed without urea (MAI-PbLyDMSO) was immediately converted to MAPbL upon heating at 65 °C, whereas a much slower conversion with an elevated temperature of 100 °C was observed with addition of urea. This effect is most likely due to the change in intermolecular interactions upon addition of urea.
  • FIG. 10 shows the adducts and urea powders used for FT-IR measurement, (A) MAI-PblrDMSO adduct, (B) urea, (C)
  • FIG. 3C shows Fourier transform infrared (FT-IR) spectra of MAI-PblrDMSO adduct, urea, MAI-PblrDMSOurea and MAI-Pblrurea adduct powder, according to an embodiment of the present disclosure.
  • the interaction of urea with MAI-PbI 2 seems to be weak in the absence of DMSO, which probably allows the formation of MAPbI 3 at lower temperature than the sublimation temperature of urea.
  • crystallization kinetic is inversely exponentially proportional to activation energy (E a ) at constant temperature.
  • FIG. 4A shows a Fourier transform infrared (FT-IR) spectra of urea (powder), MAPbI 3 (film) and MAPbI 3 with 4 mol% urea (film), according to an embodiment of the present disclosure.
  • FIGS. 4C and 4D show x- ray diffraction patterns of the bare MAPbI 3 film and with urea, according to embodiments of the present disclosure.
  • FIGS. 13A and 13B show X-ray diffraction patterns of urea (powder) and perovskite film without and with 10 mol% and 20 mol% urea, respectively, according to embodiments of the present disclosure.
  • FIG. 5A shows atomic force microscopic images (AFM) of bare MAPbI 3 , according to an embodiment of the present disclosure.
  • FIG. 5B shows atomic force microscopic images (AFM) of MAPbI 3 with 4 mol% urea on Sn02 coated ITO substrates, according to an embodiment of the present disclosure.
  • FIG. 5C is a cross sectional scanning electron microscopic (SEM) image of perovskite solar cells based on bare MAPbI 3 , according to an embodiment of the present disclosure.
  • SEM scanning electron microscopic
  • 5D is a cross sectional scanning electron microscopic (SEM) image of perovskite solar cells based on MAPbI 3 with 4 mol% urea, according to an embodiment of the present disclosure.
  • SEM scanning electron microscopic
  • AFM atomic force microscopic
  • the perovskite film with urea addition displayed single interfaces of large grains along the direction perpendicular to the substrate, whereas the bare MAPbI 3 film shows multiple interfaces between several smaller grains.
  • the enlarged grains were also confirmed in the top-view SEM images provided in FIGS. 14A- 14F, where nano-sized bumps were observed on the surface of MAPbI 3 grains with addition of 4 mol% urea.
  • FIG. 6A shows UV-Vis and photoluminescence (PL) of the MAPbI 3 perovskite films measured to evaluate the effect of added urea on absorption and charge carrier properties of the film, according to an
  • FIG. 15 shows 1-transmittance curves of MAPbL- film without and with 4 mol% urea, in which open circles are measured data and solid lines are linear fit of the data. Inset shows magnified absorption onset region, related to FIGS. 6A-6D. From closer inspection of (1-transmittance) spectra in FIG.
  • FIG. 6B shows the PL intensity versus wavelength indicating the steady- state, according to an embodiment of the present disclosure. Notably, the PL peak intensity was increased more than three times from 0.9114 x 10 5 to 3.1839 x 10 5 upon addition of urea.
  • FIG. 6C shows time resolved PL decay profiles of the MAPbL films monitored at the peak emission (770 nm) to find the origin of the enhanced PL intensity, according to an embodiment of the present disclosure.
  • the fitted parameters are demonstrated in Table 2.
  • the fast component (xi) might be related to trap- mediated monomolecular non-radiative recombination derived by defects at grain boundaries. It has been reported that trap-mediated non-radiative recombination becomes dominant with a low intensity of excitation due to slow depopulation of charge carriers from trap states.
  • FIGS. 16A and 16B shows the time-resolved PL spectra of bare MAPbL films under different intensities of excitation.
  • the PL decay profile of MAPbL film with 4 mol% urea shows a single exponential decay with ⁇ 2 ⁇ 700 ns regardless of the excitation intensity, which suggests a significantly decreased defect density after addition of urea.
  • ⁇ 2 which is associated with bimolecular radiative recombination in bulk of the perovskite film, was highly increased from 200.5 ns to 752.4 ns with addition of urea. This indicates that the charge carrier lifetime is highly prolonged, which likely contributes to the enhanced Voc and FF observed.
  • FIG. 6D shows the decrease in defect density with addition of urea can be attributed to increased grain size due to slower crystallization with higher activation energy during the crystallization, resulting in decreased grain boundaries and their associated defects, according to an embodiment of the present disclosure.
  • the urea Lewis base is likely precipitated at grain boundaries in the final film that serves to passivate the grain boundary defect sites and remove trap states, which will facilitate the charge transport and enhance the quasi-Fermi level and thereby Voc
  • FIG. 17 depicts absorption spectra of MAPbL film without and with 4 mol% urea, according to an embodiment of the present disclosure.
  • the precursor solution was diluted by 5 times (10.4 wt%) compared to one used for device fabrication (51.8 wt%).
  • the precursor solutions were diluted five times to decrease the thickness of MAPbL films.
  • increase in absorption from 420 nm to 500 nm was reproducibly observed after addition of urea.
  • V bi dC ⁇ Vu represents the built-in potential
  • W denotes the depletion width
  • C is the
  • FIG. 7A shows the Vm and W measured using Mott-Schottky plot in which the measured VbiS were 1.05 V and 1.17 V for the devices without and with urea respectively, correlating with enhanced Voc with urea, according to an embodiment of the present disclosure.
  • FIG. 7B shows the calculated ⁇ from frequency dependent capacitance spectra shown in FIG. 7A, according to an embodiment of the present disclosure.
  • urea effectively reduce the trap state originated from grain boundaries.
  • FIG. 18A shows photovoltaic parameters of MAPbI 3 perovskite solar cells with different concentration of urea solution used for post-treatment for short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE), according to embodiments of the present disclosure.
  • FIG. 18B shows photovoltaic parameters steady-state PCE, according to an embodiment of the present disclosure.
  • FIG. 18C shows external quantum efficiency (EQE) spectra of best performing device without spin-coating of 27 mM urea solution, according to an embodiment of the present disclosure.
  • EQE external quantum efficiency
  • FIGS. 19A and 19B are schematics showing (A) bare MAPbI 3 and (B) MAPbI 3 film with post-treatment of urea, according to embodiments of the present disclosure.
  • FIGS. 19C and 19D show steady-state and time resolved photoluminescence (PL) decay profiles of the film with and without urea post-treatment, respectively, measured to investigate the origin of the improved photovoltaic performance, according to embodiments of the present disclosure.
  • steady-state PL intensity was increased more than 2 times after post-treatment of urea solution.
  • FIG. 19C steady-state PL intensity was increased more than 2 times after post-treatment of urea solution.
  • FIG. 20 shows a comparison of photovoltaic parameters of perovskite solar cells based on bare MAPbI 3 , MAPbI 3 film with spin-coating of 27 mM urea solution and MAPbI 3 film prepared with addition of 4 mol% urea, short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE), according to embodiments of the present disclosure.
  • Jsc short-circuit current density
  • Voc open-circuit voltage
  • FF fill factor
  • PCE power conversion efficiency
  • FIGS. 21A and 21B show scanning electron microscopic (SEM) images of MAPbI 3 film with 50 mol% urea, according to an embodiment of the present disclosure. Yellow arrows in the image indicate secondary phase formed at grain boundaries. From the SEM images of the MAPbI 3 perovskite film with 50 mol% urea (FIGS. 21 A and 21B), we identified the formation of the secondary phase at grain boundaries (yellow arrows in FIGS. 21A and 21B).
  • FIG. 7C is a scanning electron microscopic (SEM) image of MAPbI 3 film with 50 mol% urea, according to an embodiment of the present disclosure.
  • FIGS. 22A and 22C are topological atomic force microscopy (c-AFM) images, according to
  • FIGS. 22B and 22D are conductivity images of bare ITO glass and with spin coating of 108 mM urea solution in 2-propanol, according to embodiments of the present disclosure.
  • DC bias voltage of 20 mV was applied during the measurement.
  • FIGS. 8A and 8B show the distribution of the measured current signal between the tip and perovskite film, which is overlaid on the topological images (gray scale), according to an embodiment of the present disclosure.
  • the current was measured under a DC bias voltage of 1.0 V in ambient atmosphere and room-light conditions.
  • the measured current was highly heterogeneous over the whole film. The heterogeneity exists between both grains and different regions of the grain interior, which is in accordance with previous studies.
  • FIG. 8C shows the trajectory of the scan of the height and current signal, in which the measured current varied significantly along the trajectory, according to an embodiment of the present disclosure.
  • the current signal was measured to be relatively higher at grain boundaries than grain interior, which was found to be due to downward bend-bending at grain boundary causing electron trapping.
  • FIG. 8D shows the current signal along the trajectory, with addition of urea, according to an embodiment of the present disclosure.
  • the current signal is overall enhanced with much better homogeneity compared to bare MAPbI 3 film.
  • the homogeneous current can be confirmed from the scan trajectory in FIG. 8D.
  • the measured current is relatively constant across the two different grains regardless of the grain boundary present between grains, indicating urea successfully passivates the grain boundaries to reduce the carrier trapping at grain boundaries.
  • FIG. 8E shows the probability distribution of the measured current from the MAPbI 3 films with and without urea, respectively, according to an embodiment of the present disclosure.
  • the overall current signal was highly increased with a narrower distribution, implying an improved mobility and/or carrier density, which is correlated with a decreased trap density and improved carrier lifetime in the PL measurement.
  • FIGS. 23A and 23B depict, respectively, ex-situ and in-situ stability test of MAPbI 3 perovskite solar cell without and with 4 mol% urea, according to embodiments of the present disclosures.
  • the devices were stored under dark in ambient condition for ex-situ measurement (FIG. 23 A) while they were maintained at maximum power point under continuous one sun illumination for in-situ measurement (FIG. 23B). While the reference device showed 43% degradation (from 17.1% to 9.8%) during 27 days, the device with urea showed 35% degradation (from 18.27% to 11.82%).
  • FIGS. 24A-24C show absorption spectra measured after exposure to one sun illumination for different time, (A) bare MAPbI 3 film and (B) MAPbI 3 with 4 mol% urea, according to embodiments of the present disclosure.
  • FIG. 24C depicts the evolution of absorbance at 600 nm as a function of light exposure time, according to an embodiment of the present disclosure. While the initial degradation was slower with urea, the degradation was accelerated after 90 min of light exposure. Further study might be required to fully understand the effect of urea additive on stability of the perovskite film and device.
  • ITO Indium doped tin oxide
  • acetone acetone
  • 2-propanol for 15 min respectively.
  • UV-ozone treatment was performed for 15 min to enhance the wettability before spin-coating of Sn0 2 precursor solution.
  • Sn0 2 layer was formed by spin-coating the precursor solution at 3000 rpm for 30 s two times. After first spin-coating, the film was dried at 150 °C for 30 min while it was heated to 150 °C 5 min followed by 180 °C for 1 h after second cycle. Perovskite layer was formed from adduct solution.
  • Sn0 2 coated substrate was treated with UV-ozone for 15 min before spin-coating the perovskite solution.
  • the perovskite solution was spin-coated at 4000 rpm for 25 s, to which 0.3 mL of diethyl ether (anhydrous, >99.0%, contains BHT as stabilizer, Sigma-Aldrich) was dropped.
  • the resulting transparent adduct film was converted to perovskite by heat-treatment at 65 °C for 1 min followed by 100 °C for 30 min.
  • the spiro-MeOTAD solution was prepared by dissolving 85.8 mg of spiro-MeOTAD (Lumtech) in 1 mL of chlorobenzene (anhydrous, 99.8%, Sigma- Aldrich) in which 33.8 ⁇ of 4-tert-butylpyridine (96%, Aldrich) and 19.3 ⁇ of Li-TFSI (99.95%), Adrich, 520 mg/mL in acetonitrile) solution were added.
  • the spiro-MeOTAD solution was spin-coated at 3000 rpm for 20 s by dropping 17 ⁇ of the solution on spinning substrate.
  • 80 nm-thick silver was thermally evaporated at 0.5 A/s to be used as an electrode.
  • Conducting atomic force microscopy Conducting atomic force microscopy (c- AFM) was measured by Bruker Dimension Icon Scanning Probe Microscope equipped with TUNA module using contact mode. The perovskite layers were prepared on Sn0 2 coated ITO substrate in which the ITO electrode was connected to the stage by silver paste. 0.01-0.025 ohm-cm Antimony (n) doped Si tip (SCM-PIC, Bruker) was used to probe the morphology and current with scan rate of 1.98 Hz.
  • Photoluminescence spectroscopy Steady-state photoluminescence (PL) was measure by a Horiba Jobin Yvon system. A 640 nm monochromatic laser was used as an excitation fluorescence source. Time resolved PL decay profile was obtained using a Picoharp 300 with time-correlated single-photon counting capabilities. A picosecond laser diode head (PLD 800B, PicoQuant) provided excitation at a wavelength of 640 nm with a repetition frequency of 100 kHz.
  • PLD 800B PicoQuant
  • Admittance spectroscopy was carried out under dark without DC bias voltage to avoid the degradation of the device during the measurement.
  • 20 mV AC sinusoidal pulses with frequency from 20 Hz to lMHz were applied to the devices.
  • the x-axis was converted from angular frequency ( ⁇ ) to ⁇ ⁇ by measuring the attempt-to-escape frequency, which was obtained from frequency-dependent capacitance plot via relaxation process instead of Arrhenius plot of characteristic frequency.
  • polycrystalline perovskite may be desirable for both the optoelectronic properties and environmental stability of solar cells as the solution-processing of perovskite films inevitably introduces many defects at grain boundaries.
  • small molecule-based additives have proven to be effective defect passivating agents, their high volatility and diffusion coefficients may not be sufficient to render polycrystalline perovskite films robust enough against harsh environmental conditions. Accordingly, we suggest design rules for selecting effective molecules by considering their molecular dipole and structure. From these, we introduce a strategy to form macromolecular intermediate phases using long chain polymers, which results, inter alia, in (1) high crystallinity, (2) enlarged perovskite grain sizes, (3) defect passivation, and (4) inter-grain cross-linking.
  • a series of adduct formations between perovskite precursors and long chain polymers can lead to the formation of a completely novel type of polymer-perovskite composite cross-linker never before reported.
  • the composite cross-linker can function to bridge the perovskite grains, facilitating grain-to-grain electrical coupling and yielding excellent environmental stability against moisture, light, and heat, the extent of which has not been attainable with small molecule defect passivating agents. As a result, all photovoltaic parameters may be significantly enhanced in the solar cells and the devices may also show excellent ambient stability.
  • Metal halide perovskites have been used in various optoelectronic applications such as photodetectors, light-emitting diodes, solar cells, X-ray imaging, and lasing due to their high absorption coefficients, long-range charge carrier diffusion lengths, and high photoluminescence (PL) quantum yield. Since the first efficient solid-state perovskite solar cell was reported in year 2012, a lot of attempts to understand the photophysical properties of perovskites and to improve the photovoltaic performance of perovskite-based solar cells have been made.
  • the characteristic grain boundaries of the polycrystalline thin films were found to function as trap states and further act as vulnerable spots to trigger the degradation of the materials and its physical properties. Because metal halide perovskite films are deposited via solution processes and crystallizes at low temperatures, a lot of structural defects exist along the grain boundaries of polycrystalline perovskite films. Grain boundaries that have dangling bonds can provide migration paths for ions and can become charge carrier trap centers and cause non-radiative recombination, which can significantly degrade charge carrier transport and the
  • perovskite films are more vulnerable to heat and moisture degradation which propagates inwards into the grain interiors from the boundaries to induce the physical and electrical decoupling of individual grains, thus reducing device performance. Therefore, it is desirable for polycrystalline perovskite films to meet several properties for optoelectronic applications including: (1) high crystallinity and large-sized crystal growth to minimize grain boundaries and structural defects at both grain interiors and boundaries, (2) effective defect passivation at grain boundaries, and (3) cross-linking of individual crystal grains for high stability against harsh environmental stresses.
  • Novel strategies were developed to meet all these requirements simultaneously by adopting a macromolecular intermediate phase induced crystallization, resulting in highly crystalline perovskites cross-linked by polymer-perovskite composites, which lays a solid platform toward both high efficiency and stability.
  • Precursors for metal halide perovskites such as Pb(II) halides (e.g., Pbl 2 , PbBr 2 or PbCl 2 ) or organic halides (CH3NH3I, HC(NH 2 ) 2 I) are known to be Lewis acids. Reaction of a Lewis acid with a Lewis base leads to either a redox reaction or an adduct formation, the latter of which is composed of the acid and base linked by a dative bond (i.e., shared electrons that originate from the Lewis base).
  • Pb(II) halides e.g., Pbl 2 , PbBr 2 or PbCl 2
  • organic halides CH3NH3I, HC(NH 2 ) 2 I
  • the intermediate adduct phase formed by such Lewis base-acid reaction cam facilitate the homogeneous crystal growth of the perovskite due to the additional Lewis-base removal process from the adduct film, which retards the formation rate constant for the perovskite.
  • This intermediate phase method has been widely used in perovskite solar cells, but the use of Lewis bases have been restricted to polar aprotic small molecules such as ⁇ , ⁇ -dimethyl sulfoxide (DMSO), urea, and N-methyl-2-pyrrolidone (NMP).
  • DMSO ⁇ , ⁇ -dimethyl sulfoxide
  • NMP N-methyl-2-pyrrolidone
  • the small molecule Lewis bases can form small molecular adducts with individual molecules of the perovskite precursors to form an intermediate phase (FIG. 25A).
  • 25A is a schematic representation of Perovskite grain growth induced by a conventional small molecular intermediate phase, according to an embodiment of the present disclosure.
  • small molecule-based defect passivating agents that have lone pair electrons on oxygen, sulfur, or nitrogen (e.g., pyridine, thiophene, and fullerenes) have been used to improve the photophysical properties of perovskites by coordinating with defect sites at grain boundaries.
  • the high degree of volatility and high diffusion coefficients of small molecules may pose difficulties in incorporating them into practical devices operated under harsh environments such as high temperature, humidity, electric field and strong light.
  • polymeric molecules are expected to provide high molecular stability and polymer-assisted cross-linking of the crystal grains of perovskite which improve the morphological and environmental stability of the perovskite films.
  • long- chain polymers might be immobilized after crystallization of the perovskite, while small molecule additives have substantial diffusion and drift mobility in the perovskite film during operation.
  • Repeating units of the long-chained polymeric Lewis base can possibly form Lewis acid-base adducts with a series of perovskite precursor molecules, so it forms a macromolecular intermediate phase with a larger degree of coordination and long-range molecular ordering along the polymer chain (FIG. 25B).
  • FIG. 25B is a schematic
  • [00128] Macromolecular Lewis acid-base intermediate phase Ethylene carbonate (EC [C3H4O3], ⁇ 5.41 ⁇ ) and propylene carbonate (PC [C4H6O3], ⁇ ⁇ 5.57 ⁇ ) as small molecule Lewis bases with different permanent dipoles and poly(propylene carbonate) (PPC, [C4H603]n) as a polymeric Lewis base were investigated in order to establish how the molecular structure of Lewis bases affect the formation of the intermediate phase and growth kinetics of CH 3 NH 3 PbI 3 .
  • PPC is a linear copolymer of carbon dioxide and propylene oxide.
  • polar solvents e.g., ⁇ , ⁇ -Dimethylmethanamide (DMF) or DMSO
  • the long chain polymer does not evaporate unlike DMSO which has a comparatively high vapor pressure.
  • Remnant polymeric Lewis bases can donate lone pair electrons from the oxygen atom to coordinate with perovskite crystal defects such as Pb 2+ or H3 + at the grain boundaries.
  • PPC is insoluble in water and its repeating unit (PC) has a hydrophobic nature (surface energy ⁇ 30 mJ/m 2 ). Therefore, PPC functions both as a cross-linker and passivation agent to enhance the moisture resistant of perovskite polycrystals in ambient conditions.
  • FIG. 25C is a schematic representation of process steps for the fabrication of a macromolecular intermediate phase-mediated growth of the perovskite film, according to an embodiment of the present disclosure.
  • DMF which has a weak Lewis basicity
  • Equimolar DMSO the most widely used Lewis-basic polar aprotic solvent, was also used to form a 1 : 1 adduct with the perovskite precursors.
  • DMSO also evaporates during high temperature annealing due to its high vapor pressure, resulting in perovskite crystals modified by polymeric Lewis bases (i.e., CH3 H3I ⁇ Pbl 2 ⁇ DMSO ⁇ Polymeric Lewis base adduct + heat ⁇ CH 3 NH 3 PbI 3 ⁇ Polymeric Lewis base).
  • the "K” spectrum corresponds to synthesized adduct powders of CH3 H3I and Pbl 2 without Lewis base.
  • the "L” spectrum corresponds to CH 3 NH 3 I-PbI 2 -DMSO.
  • the red spectrum corresponds to
  • FIGS. 26E-26H show X-ray diffraction spectra of synthesized CFL FLI-PblrDMSO (e), CFL FLI-PblrDMSO-PPC adduct powders (f), CFL FLPbL (g) and CFL HsPbL-PPC perovskite films (h), according to embodiments of the present disclosure.
  • FIG. 27A is a scanning electron microscopy image of CH 3 NH 3 PbI 3 film, according to an embodiment of the present disclosure.
  • FIG. 27B is a scanning electron microscopy image of CFb FLPbL-PPC film, according to an embodiment of the present disclosure.
  • FIG. 27C is a transmission electron microscopy (TEM) of cross-linked perovskite grains at lower magnification, according to an embodiment of the present disclosure.
  • FIG. 27D is a transmission electron microscopy (TEM) of perovskite-polymer composite cross- linker between adjacent grains (highlighted region in FIG. 27C), according to an embodiment of the present disclosure.
  • FIG. 27E is an Inverse Fast Fourier transform (IFFT) image of the region highlighted in FIG. 27C.
  • IFFT Inverse Fast Fourier transform
  • Region (1) in FIG. 27D corresponds to a region within the perovskite-polymer bridge.
  • Region (2) in FIG. 27D corresponds to a boundary of the perovskite-polymer composite cross-linker.
  • FIG. 27F is an enlargement of region (2) in the image shown in FIG. 27D showing the interface or bridge between the polymer and the perovskite.
  • FIG. 27G is a schematic diagram of various stages of a process for producing cross-linking between perovskite crystals using the polymer, according to an embodiment of the present disclosure.
  • the interaction energies between CH3 H3 + and PPC with different numbers of repeating units were also calculated and was shown to be higher for longer PPC chain lengths (e.g., the interaction energy of CH3 H3 + -DMSO-PPC with four repeating units is -2.283 eV) (FIGS. 28A-28E and Table 7).
  • Table 7 lists photovoltaic parameters of solar cells of bare CH 3 H 3 Pbl3 and CH 3 H 3 Pbl3 with Lewis bases added.
  • FIG. 28A depicts Reflective Fourier transform infrared (FTIR) spectra of the perovskite films without and with various types of Lewis bases (EC, PC, and PPC), according to embodiments of the present disclosure.
  • FIG. 28C shows most favorable Pb 2+ perovskite surface adsorption configurations of the Lewis bases and their calculated binding energies, according to embodiments of the present disclosure.
  • FIG. 28D shows photoluminescence (PL) spectra (inset: normalized PL spectra) of perovskite films without and with Lewis bases, according to embodiments of the present disclosure.
  • the donation of the lone pair electrons of the oxygen of the Lewis bases to CH 3 H3 + and Pbl 2 results in the formation of a CH 3 H 3 I ⁇ Pbl 2 ⁇ DMSO ⁇ Lewis base adduct, and the addition of a Lewis base with a higher permanent dipole can more chemically stabilize the adduct formation.
  • the crystallization rate parameter is exponentially proportional to the inverse of the activation energy (E a ).
  • the XRD spectra of the synthesized adduct powders with DMSO or PPC exhibited low angle peaks ⁇ 10 0 due to the longer interplanar distances of the adducts relative to that of the pure perovskite. It was observed that most of peaks disappeared after crystallization. Thus, the XRD peaks of the powder adduct can provide information on the molecular ordering of the intermediate phases (shown in FIGS. 27E and 27F).
  • Polymeric Lewis bases dramatically increased the intensity of the intermediate phase XRD peaks that originated from the Lewis acid-base-adducts, as compared to the case with DMSO.
  • Polymeric Lewis bases reduced the full width at half maximum (FWUM) of the main peak at 8 0 from 0.134 to 0.115, indicating a greatly enhanced molecular ordering of the intermediate phase induced by the long-chain polymer. Additionally, a significant increase in the XRD peak intensities at high angles was also seen, further confirming the improved long-range molecular ordering of the intermediate phase (FIGS. 26E and 26F). After crystallization, peak intensities of perovskite films also increased with polymeric Lewis bases. The addition of PPC increased the (110) peak by -30% and reduced its FWUM from 0.142 to 0.121 (FIGS.
  • FIGS. 29A-29D show atomic force microscopy images of the obtained perovskite- polymer, according to an embodiment of the present disclosure.
  • Atomic force microscopy was used to confirm the enlarged grain sizes induced by the polymer (images i, j, k, 1 in FIGS. 29A-29D).
  • small molecular Lewis bases EC and PC
  • crystal grains grown with the polymeric Lewis base were much larger than those grown with the small molecules (images i, k, 1 in FIGS. 29A, 29C and 29D).
  • FIG. 27C visualizes the cross-linking of two grains separated from the perovskite film.
  • Fig. 27D is a magnified TEM image from the highlighted region of FIG. 27C (cross-linker of two grains).
  • FFT Fast Fourier transform
  • FIG. 27D shows an interplanar spacing of 3.1 A, which matches well with the (110) reflection of cubic CH 3 NH 3 PbI 3 .
  • the inverse FFT image magnified on highlighted region 2 clearly shows the formation of a perovskite-polymer composite bridge between two grains (FIG. 27F).
  • the macromolecular intermediate phase decreases the nucleation probability and thus slows down the rate of nucleation, thereby decreasing the number of nuclei.
  • a relatively small amount of nuclei nucleate without high energy barriers and subsequently grow continuously without impingement to form large grains.
  • stage II the bounded perovskite precursors within the polymeric adducts can be crystalized by overcoming the increased activation energy barrier for nucleation, and such crystals grown in the proximity of long-chain polymers are immobilized by the surrounding polymer chains and interconnect large grains with polymers (FIG. 27G).
  • the binding energies were calculated to be -19.4 kJ/mole, -31.5 kJ/mole and -34.5 kJ/mole for EC, PC and PPC, respectively.
  • the grain boundary defects are predominantly iodide ( ⁇ ) vacancies.
  • the interaction between the Lewis bases and the perovskite might be a dipole-ion interaction between the lone pair electrons of the Lewis bases and under-coordinated Pb atoms at the grain boundaries. Therefore, the stronger binding energy when PC was added in comparison to the case with EC can be correlated with the stronger dipole moment of the former (5.57D) relative to the latter (5.42D).
  • the inset of FIG. 28E shows average PL lifetimes of the films.
  • the relatively faster decay components ( ⁇ 20 ns) are attributed to charge carrier trapping defect states, while the slower decay components ( ⁇ 2 >20 ns) are assigned to bimolecular radiative recombination in the bulk crystals.
  • ⁇ 2 was enhanced from 49.6 ns (bare CH 3 NH 3 PbI 3 ) to 87.7 ns (EC) and 99.4 ns (PC), suggesting that the Lewis bases also elongate charge carrier lifetimes within the bulk crystal.
  • the average PL lifetime was greatly enhanced from 18.4 ns to 56.5 ns (EC) and 99.4 ns (PC).
  • the lower defect density with reduced grain boundaries passivated by EC and PC might be the origin of the reduced charge carrier trapping while the elongated ⁇ 2 can be ascribed to larger crystallite sizes as observed by the XRD and AFM measurements (FIGS. 26A-26H).
  • Addition of PPC, instead of the small molecules, further elongated the PL lifetime.
  • the longer PL lifetime with PPC as compared to the cases with the small molecular Lewis bases can be related to the larger crystallite sizes and higher binding energy of PPC.
  • the ⁇ 2 with PPC (120.4 ns) is considerably higher than those of the films with EC (87.7 ns) and PC (99.4 ns).
  • the larger ⁇ 2 indicates a longer bulk carrier lifetime owing to the much larger-sized crystal grains and the inter-grain cross-linking induced by the long-range ordered intermediate phase as observed in the AFM and TEM analysis.
  • FIG. 30A shows X- ray diffraction spectra of bare CH 3 NH 3 PbI 3 and CH 3 NH 3 PbI 3 -PPC (0.3 and 5.0 wt%) films against moisture (relative humidity: 70+5%), according to an embodiment of the present disclosure.
  • FIG. 30B shows X-ray diffraction spectra of bare CH 3 H 3 PbI 3 and CH 3 H 3 PbI 3 PPC (0.3 and 5.0 wt%) films against light (1.5 AM), according to an
  • FIG. 30C shows X-ray diffraction spectra of bare CH 3 H 3 PbI 3 and CH 3 H 3 PbI 3 -PPC (0.3 and 5.0 wt%) films against heat (100 °C), according to an embodiment of the present disclosure.
  • FIG. 30D shows photovoltaic parameters of CH 3 H 3 PbI 3 perovskite solar cells with the addition of different Lewis bases: short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE), according to an embodiment of the present disclosure.
  • Jsc short-circuit current density
  • Voc open-circuit voltage
  • FF fill factor
  • PCE power conversion efficiency
  • FIG. 30E shows a current density-voltage (J-V) characteristics of bare CH 3 H 3 PbI 3 and CH 3 H 3 PbI 3 -PPC, according to an embodiment of the present disclosure.
  • FIG. 30E shows PCE percentage evolution in ambient conditions as a function of time of CH 3 H 3 PbI 3 -based solar cells without and with PPC, according an embodiment of the present disclosure.
  • the environmental stability of the perovskite films modified using the polymeric Lewis bases was assessed against a control in different kinds of harsh environmental stresses that degrade perovskites (i.e., moisture, light, and heat) (FIGS. 30A-30C).
  • a moisture stability test was conducted in an isolated chamber with 70+5% relative humidity (RH) for 150 hrs. Separately, the films were kept under constant light illumination at AMI .5 one-sun for 2hrs to investigate the influence of light on the perovskite films. Also, thermal stability was tested by heating the films at 100 °C in a nitrogen atmosphere for 66 hrs.
  • the bare CH 3 H 3 PbI 3 films were observed to severely decompose to Pbl 2 in each case, confirmed by a substantial increase in the XRD peaks of the films at -12.5 0 and also by a decreased absorption of the films (FIGS. 30A-30C).
  • the perovskite films added with PPC retained relatively high amounts of CH 3 H 3 PbI 3 compared to that of the bare perovskite films.
  • the degradation of the CH 3 H 3 PbI 3 films was further retarded, supporting the conclusion that the improved environmental stability originated from the addition of the PPC and their inter- grain cross-linking effect.
  • FIG. 30D Photovoltaic performance of the perovskite solar cells with different Lewis base additions were compared, as shown in FIG. 30D.
  • the devices incorporated a planar heteroj unction structure with an architecture of ITO/Sn0 2 /perovskite/spiro-MeOTAD/Ag. All the photovoltaic parameters were enhanced with incorporation of the Lewis bases (FIG. 30D).
  • the short-circuit current density (Jsc) was marginally enhanced from 21.79 ⁇ 0.39 mA/cm 2 to 22.05 ⁇ 0.28 mA/cm 2 (1.2% improvement) and 22.38 ⁇ 0.12 mA/cm 2 (2.7% improvement), with the addition of EC and PC, respectively.
  • Voc open-circuit voltage
  • FF fill factor
  • the improved Jsc can be correlated with an improved absorbance at longer wavelengths, which is likely due to an enhanced light scattering by the larger grains.
  • the stabilized PCEs were also measured to be 19.47% for the device added with PPC and 16.94% for bare CH 3 H 3 PbI 3 .
  • the observed reduced initial decay can be attributed to a decreased defect density as a result of the PPC-induced crystal modification.
  • the addition of PPC slowed down the subsequent linear decay regime, whereby the fitted slope was decreased from -9.5xl0 "4 to -4.9 xlO "4 .
  • the calculated T 8 o lifetimes (time taken for the PCE to degrade to 80% of its initial value) of the devices were significantly elongated from 211.0 h to 404.2 h with addition of the polymeric Lewis base.
  • the slower decay has been related to an irreversible degradation of the perovskite layer accompanied by chemical reaction and morphological change. Therefore, the inter-grain cross-linking of the perovskite, induced by the macromolecular intermediate phase, could very well have retarded the irreversible degradation of the perovskite.
  • a polymeric Lewis base with high dipole moment Lewis basic repeating units was employed into CH 3 NH 3 PbI 3 .
  • the polymer facilitated the formation of a long-range, molecularly-ordered intermediate phase via a series of Lewis base adduct formations with the perovskite precursors (CH3 H3I and Pbl 2 ).
  • the formation of such a macromolecular adduct increased the activation energy for nucleation and diffusion of the precursor molecules, such that the subsequent perovskite films were fabricated with high crystallinity and significantly enlarged grains.
  • Remnant polymeric Lewis bases in the perovskite films also effectively passivated the defect sites at the grain boundaries with high binding energies.
  • the long-range ordering of the perovskite precursor molecules along the polymer backbone enabled inter-grain cross-linking to form a polymer-perovskite composite bridge which facilitated inter-grain electrical coupling and greatly improved the stability of the perovskite films under harsh environmental conditions.
  • all the photovoltaic parameters of the devices including Jsc, Voc, and FF were enhanced, and a highest PCE of 20.06%

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Abstract

La présente invention concerne une composition de précurseur permettant de produire une couche active de pérovskite d'un dispositif photovoltaïque. La composition comprend un premier composant comprenant une pluralité de premières molécules d'une structure pérovskite à former par une combinaison de produits d'addition; un second composant comprenant une pluralité de secondes molécules de la structure pérovskite à former par la combinaison de produits d'addition; et une base de Lewis non volatile. La base non volatile est non volatile au-dessus d'une première température et en dessous d'une seconde température, la seconde température étant supérieure à la première température. La couche active de pérovskite peut être utilisée pour produire un dispositif photovoltaïque.
PCT/US2018/044658 2017-07-31 2018-07-31 Additif de base de lewis bifonctionnel pour une homogénéité microscopique dans des cellules solaires de pérovskite Ceased WO2019028054A1 (fr)

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CN112382725A (zh) * 2020-11-06 2021-02-19 中国科学院青岛生物能源与过程研究所 一种降低有机-无机杂化钙钛矿薄膜离子迁移的方法
CN113921721A (zh) * 2021-09-29 2022-01-11 湖北大学 一种全透明钙钛矿薄膜、器件、制备方法以及应用
CN114914363A (zh) * 2022-05-27 2022-08-16 西安电子科技大学 一种高效稳定钙钛矿太阳能电池及其制备方法
WO2025165177A1 (fr) * 2024-02-02 2025-08-07 한화솔루션 주식회사 Agent de revêtement pour former un film mince de pérovskite de grande surface et procédé de formation d'un film mince de pérovskite de grande surface l'utilisant
DE102024104351A1 (de) * 2024-02-16 2025-08-21 Albert-Ludwigs-Universität Freiburg, Körperschaft des öffentlichen Rechts Verfahren zum Ausbilden einer Perowskitschicht einer photovoltaischen Solarzelle

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112382725A (zh) * 2020-11-06 2021-02-19 中国科学院青岛生物能源与过程研究所 一种降低有机-无机杂化钙钛矿薄膜离子迁移的方法
CN112382725B (zh) * 2020-11-06 2023-03-24 中国科学院青岛生物能源与过程研究所 一种降低有机-无机杂化钙钛矿薄膜离子迁移的方法
CN113921721A (zh) * 2021-09-29 2022-01-11 湖北大学 一种全透明钙钛矿薄膜、器件、制备方法以及应用
CN114914363A (zh) * 2022-05-27 2022-08-16 西安电子科技大学 一种高效稳定钙钛矿太阳能电池及其制备方法
WO2025165177A1 (fr) * 2024-02-02 2025-08-07 한화솔루션 주식회사 Agent de revêtement pour former un film mince de pérovskite de grande surface et procédé de formation d'un film mince de pérovskite de grande surface l'utilisant
DE102024104351A1 (de) * 2024-02-16 2025-08-21 Albert-Ludwigs-Universität Freiburg, Körperschaft des öffentlichen Rechts Verfahren zum Ausbilden einer Perowskitschicht einer photovoltaischen Solarzelle
WO2025172137A1 (fr) * 2024-02-16 2025-08-21 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V. Procédé de formation d'une couche de pérovskite d'une cellule solaire photovoltaïque

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