WO2019036093A2

WO2019036093A2 - Wrapping perovskite grains with silica shells for improving stability and efficiency of perovskite electronic devices

Info

Publication number: WO2019036093A2
Application number: PCT/US2018/037619
Authority: WO
Inventors: Jinsong Huang; yang BAI
Original assignee: NuTech Ventures Inc
Current assignee: NuTech Ventures Inc
Priority date: 2017-06-14
Filing date: 2018-06-14
Publication date: 2019-02-21
Anticipated expiration: 2019-12-14
Also published as: WO2019036093A3

Abstract

Systems and methods for enhancing the stability and efficiency of perovskite materials, and devices incorporating such perovskite materials. A method of making a perovskite layer includes mixing a perovskite solution with a silica shell precursor solution to produce a perovskite-silica precursor solution, and spin casting or drop casting the perovskite-silica precursor solution on a substrate to form a perovskite material or material layer, wherein the perovskite material or material layer includes a plurality of groups of one or more perovskite grains, each of said plurality of groups wrapped in a silica shell. The silica shell precursor solution may have a chemical structure of R_n-Si-(OR)_4-n, where "R" is an alkyl, aryl, or organofunctional group, and "OR" is a methoxy, ethoxy, or acetoxy group.

Description

WRAPPING PEROVSKITE GRAINS WITH SILICA SHELLS FOR IMPROVING STABILITY AND EFFICIENCY OF PEROVSKITE ELECTRONIC DEVICES

CROSS-REFERENCES TO RELATED APPLICATIONS

{0001 ) This application claims the benefit of U.S. Provisional Patent Application Serial No. 62/519,325, filed June 14, 2017, the disclosure of which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with Government support under project numbers N00014- 17-1-2163 by the Office of Naval Research and DE-EE006709 by the Department of

Energy. The Government has certain rights in the invention.

BACKGROUND

[0003] Inorganic-organic halide perovskites represent a major break-through in the development of highly efficient photovoltaic materials. For example, within only several years, polycrystalline thin-film perovskite photovoltaic ("PV") devices have achieved power conversion efficiency ("PCE") of 22.1%. The rapid rise in PCE, coupled with the prospect of low-cost precursors and facile synthesis, render perovskite photovoltaic devices highly competitive for commercial applications.

[0004] There is still a need for improved perovskite materials and perovskite-based devices, particularly for photovoltaic applications.

BRIEF SUMMARY

[0005] The present disclosure provides systems and methods for enhancing the stability and efficiency of perovskite materials, and devices incorporating such perovskite materials. Enhancing the stability of perovskite materials advantageously increases the lifetime of any electronic devices, such as solar cells, incorporating perovskite materials as an active layer.

[0006] Certain embodiments provide methods for in-situ coating or wrapping perovskite grains with a thin layer silica (S1O2) shell to stabilize the perovskite. Most inorganic matrix materials are mechanically robust and airtight. Among them, silica is an attractive coating material due to its stability against environmental and chemical factors and excellent optical properties. A method to wrap the perovskite grains (e.g., one or more grains per wrapping) with silica shells to protect the perovskite grains includes mixing silica precursors in perovskite precursor solution. During the formation of perovskite grains, the silica precursor is converted to silica by hydrolysis or other type of reaction. This results in wrapping the perovskite grains with a waterproof silica shell without sacrificing the electronic transport properties with a well- controlled shell thickness and wrapping chemistry. The silica shell layer protects perovskite grain surfaces from defect-generation and provides a passivation function, as evidenced by the dramatically elongated charge recombination lifetime, and thus increases the efficiency of electronic devices incorporating perovskite materials. Preliminary studies indicate the perovskite materials showed much better resistance to moisture-induced degradation of perovskite films after wrapping with a silicon-based coating layer. This method is useful for all perovskite \- related electronic devices, including photovoltaic devices such as solar cells.

[0007] According to an embodiment, a device including a perovskite layer is provided wherein the perovskite layer includes a plurality of perovskite grains, each grain wrapped in a silica shell.

[0008] According to another embodiment, a device including a perovskite layer is provided, wherein the perovskite layer includes a plurality of groups of one or more perovskite grains, each of said plurality of groups wrapped in a silica shell.

[0009] According to yet another embodiment, a method of forming a perovskite layer is provided wherein the perovskite layer includes a plurality of groups of one or more perovskite grains, each of said plurality of groups wrapped in a silica shell.

[0010] According to yet a further embodiment, a method of making or forming a perovskite layer is provided, which includes mixing a perovskite solution with a silica shell precursor solution to produce a perovskite-silica precursor solution, and spin casting or drop casting the perovskite-silica precursor solution on a substrate to form a perovskite material or material layer, wherein the perovskite material or material layer includes a plurality of groups of one or more perovskite grains, each of said plurality of groups wrapped in a silica shell. In certain aspects, the silica shell precursor solution has a chemical structure of Rn-Si-(OR)4-n, where "R" is an alkyl, aryl, or organofunctional group, and "OR" is a methoxy, ethoxy, or acetoxy group.

[0011 j According to a further embodiment, a semiconductor device is provided that includes a cathode layer, an anode layer, and an active layer disposed between the cathode layer and the anode layer, where the active layer includes a perovskite layer, wherein the perovskite layer includes a plurality of groups of one or more perovskite grains, each of said plurality of groups wrapped in a silica shell.

(0012] According to the various embodiments, in certain aspects, the perovskite material or layer includes organometal trihalide perovskite (grains) having the formula ABX₃, or A2BX4, wherein A is methylammonium (CH₃ H₃ ⁺), formamidinium (H2NCHNH₂ ⁺), or an alkali-metal ion, B is a metal cation, and X is a halide anion, thiocyanate (SCN^") or a mixture thereof. In certain aspects, the perovskite layer includes perovskite (grains) having the formula MAPbI₃, FAi-xMAxPb(Ii-xBr_x)₃, CsPb(Ii-xBr_x)₃, Cs_yFAi-x-_yMAxPb(Ii-xBr_x)₃, RbzCs_yFAi-x-_y-zMA_xPb(Ii- xBr_x)₃, or RbzCs_yFAi-x-_y-zMAxPbnSni-n(Ii-xBr_x)₃ where x, y, z, and n may be between 0 and 1.

[0013] According to the various embodiments, in certain aspects, the silica shell precursor solution has a chemical structure of Rn-Si-(OR)4-n, where "R" is an alkyl, aryl, or

organofunctional group, and "OR" is a methoxy, ethoxy, or acetoxy group.

[0014] Reference to the remaining portions of the specification, including the drawings and claims, will realize other features and advantages of the present invention. Further features and advantages of the present invention, as well as the structure and operation of various

embodiments of the present invention, are described in detail below with respect to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0015j The detailed description is described with reference to the accompanying figures. The use of the same reference numbers in different instances in the description and the figures may indicate similar or identical items.

[0016] FIG. 1 shows a method of coating perovskite grains with silica shells according to an embodiment.

[0017j FIG. 2A shows an SEM image of a MAPbL film.

[0018] FIG. 2B shows an SEM image of a MAPbl3@Si02 film according to an embodiment.

[001.9] FIG. 2C shows FTIR spectra of MAPbL film and MAPbl3@Si0₂ films according to an embodiment.

[0020] FIG. 2D shows an EDX element line scan profile acquired across the cross-section of a MAPbl3@Si0₂ film according to an embodiment.

[0021] FIG. 3 A shows the photocurrent density-voltage (J-V) characteristics of a perovskite devices (e.g., solar cells) based on conventional perovskite films and different silica-wrapped perovskite films.

[0022] FIG. 3B shows EQE of an optimized silica-wrapped perovskite device.

[0023] FIG. 3C shows Statistics of the Voc for devices with conventional and silica-wrapped perovskite films.

[0024] FIG. 3D shows the PCE distribution for devices with conventional and silica-wrapped perovskite films.

[0025] FIG. 4 A shows normalized time resolved PL decay curves of the MAPbL and MAPbl3@Si0₂ films on glass substrates.

[0026] FIG. 4B shows transient photovoltage decay curves of perovskite devices based on MAPbL and MAPbl3@Si0₂ films under one sun illumination.

[0027] FIG. 4C shows total density of states (DOS) of perovskite devices fabricated with MAPbL and MAPbI₃@Si0₂ films.

[0028] FIG. 5 A shows XRD of MAPbL and MAPbI₃@Si0₂ films after storage in air.

[0029] FIG. 5B shows photovoltaic performance of the typical perovskite solar cells based on conventional perovskite film and silica-wrapped perovskite film exposed to an ambient environment without encapsulation as a function of storage time; air humidity varies from 20 RH% to 70 RH%.

[0030] FIG. 6A shows photocurrent-voltage (J-V) characteristics of solar cells based on conventional and silica-wrapped FA/MA hybrid perovskite films.

[0031] FIG. 6B shows EQE of an optimized device with silica-wrapped perovskite.

[0032j FIG. 6C shows steady-state photocurrent and efficiency at the maximum power point

(1.00 V) of an optimized device with silica-wrapped perovskite.

[0033] FIG. 7 shows photovoltaic performance of typical perovskite solar cells based on conventional and silica- wrapped FA/MA hybrid perovskite films under continuous AM 1.5 one sun illumination with encapsulation as a function of illumination time.

DETAILED DESCRIPTION

(0034) FIG. 1 illustrates a method of coating perovskite grains with silica shells according to an embodiment. FIG 1 illustrates schematically a process of in-situ coating perovskite grains with silica shells and device structure of the silica-coated perovskite planar heteroj unction solar cells. In certain embodiments, tetraethyl orthosilicate (TEOS) is used as a silica precursor as TEOS can be readily hydrolyzed to form S1O2 over perovskite grains when contacting with the low-content water in toluene. The silica-coated perovskite films may be used for fabrication of p- i-n solar cells, which have a general structure of transparent conductive oxide (TCO)

electrodes/hole transport material (HTM)/perovskite/electron transport materials (ETM)/cathode. For in-situ coating perovskite grains with silica shells, TEOS is used as a silica precursor included into the perovskite precursor solution according to an embodiment. The low content moisture or OH- group containing organic molecules in the film environment drives the hydrolysis of TEOS, which builds silica shells around perovskite grains. The typical reaction and coating process is illustrated in FIG. 1. The description below is based on the perovskite material of CFbNFbPbb (MAPbb) and TEOS, but the methodology is applicable to other perovskite materials and silica precursors with a general material selection rule described herein. A p-i-n structure perovskite solar cell is used merely as an example to demonstrate the various concepts, but an n-i-p device structure, or other device structures incorporating the various perovskite materials, can also apply the same or similar concepts.

[0035]

[0036] In an embodiment, a perovskite layer is formed on a substrate. In a first step, a perovskite solution with a silica shell precursor solution to produce a perovskite-silica precursor solution, and in a second step, the perovskite-silica precursor solution is formed, e.g., via spin casting or drop casting or other deposition method, on the substrate to form a perovskite layer, wherein the perovskite layer includes a plurality of groups of one or more perovskite grains, each of said plurality of groups wrapped in a silica shell. The substrate may include, for example, glass or ITO/glass or other rigid or semi rigid material. The substrate may also include other intermediary layers as desired, for example a hole transport material, electrode materials, etc.

[0037] In the specific example shown in FIG. 1, a hole transport material (HTM) layer, e.g., a layer of poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA) film, is deposited onto a substrate, e.g., ITO/glass substrate or TCO. For example, the HTM may be deposited by spin- coating 0.2 wt% PTAA in toluene at 4000 r.p.m for 35 s. The as-prepared film may then be thermally annealed, e.g., at 100 °C for 10 min. MAPbb films may be fabricated by one-step spin coating with an anti-solvent extraction approach, for example as described in Chen, B , et al ., Efficient Semitransparent Perovskite Solar Cells for 23.0%-Efficiency Perovskite/Silicon Four- Terminal Tandem Cells. Advanced Energy Materials, 2016. The perovskite precursor solution (PVS solution) may be prepared by dissolving Phh and MAI in DMF and DM SO (e.g., 461 rng Pbli and 159 mg MAI in 700 μΐ, DMF and 78 μΐ, DMSO). For silica-coated perovskite film deposition, a silica shell precursor is blended into or mixed with the perovskite precursor. In this particular example, TEOS was used as the silica shell precursor and was blended into the perovskite precursor solution. To determine optimized device performance, different ratios of TEOS were introduced into the perovskite precursor solutions. Tl, T2, and T3 represent the devices fabricated using 3 vol%, 5 vol%, and 10 vol% TEOS modified perovskite precursor solution, respectively. The MAPbls precursor solution (mixed with silica shell precursor) was deposited onto a substrate (e.g., spun onto PTAA at 2000 r.p.m for 2 s and 4000 r.p.m for 20 s). The sample was drop-casted with toluene (e.g., 120 μΕ toluene at 8 s of the second-step spin- coating). Subsequently, the sample was annealed (e.g., at 65 °C for 10 min and 100 °C for 10 min). The electron-transporter layer (e.g., PCBM) is deposited on or coated (e.g., by spinning 2 wt% PCBM in dichlorobenzene at 6000 r.p.m for 35 s) on the perovskite layer and then annealed (e.g., at 100 °C for 30 min). Thereafter, the electrode layers are formed. For example, 20 nm C60 and 8 nm bathocuproine (BCP) were sequentially deposited by thermal evaporation, and 80 nm Cu was deposited by thermal evaporation as the device cathode.

[0038j Top-view scanning electron microscopy (SEM) was employed to characterize a S1O2 wrapped perovskite film. Compared with the bare perovskite film shown in FIG. 2A, the grain boundaries (GBs) were obscure in S1O2 wrapped perovskite film as shown in FIG. 2B, which indicates that the top surface and GBs of perovskite has been well coated with a layer of S1O2. Fourier transform infrared spectroscopy (FTIR) transmission spectra of both MAPbb and MAPbl3@Si02 (S1O2 wrapped MAPbb perovskite) films were collected to verify the formation of the S1O2 layer. Perovskite films on ITO substrates with and without S1O2 wrapping layers were prepared by following the same procedure as that for device fabrication above and the collected powder was subjected to FTIR analysis. As shown in FIG. 2C, the appearance of a new and wide vibration peak between 1, 101 and 1,035 cm^"1 confirms the formation of Si-O-Si bonds. To investigate and further confirm the formation of S1O2 wrapping layer, bulk

compositional analysis for the S1O2 wrapped perovskite film was performed with energy- dispersive X-ray spectroscopy (EDX). FIG. 2D shows the EDX element line scan profile acquired across the cross-section of the film; the majority of S1O2 was distributed at the GBs, indicating the formation of a S1O2 wrapping layer.

[0039] FIG. 3A shows the photocurrent density-voltage (J-V) characteristics of perovskite devices (e.g., solar cells) based on conventional perovskite films and different silica-wrapped perovskite films. A typical perovskite device had a short-circuit current density (Jsc) of 22.3 mA cm^"2, an open-circuit voltage (Foe) of 1.09 V, and a fill factor (FF) of 76.5% yielding a moderate PCE of 18.6%, which is consistent with previous reported work. When 3 vol% TEOS was blended into the precursor solution, the device Voc and FF increased to 1.12 V and 77.4%, respectively. The device employing silica-wrapped perovskite delivered an efficiency of 19.3%. By adding 5 vol% TEOS, the optimized performance was achieved exhibiting a Jsc of 22.7 mA cm^"2, a Voc of 1.15 V, and a of 80.9%, yielding a PCE οΐ2\ Λ%. The integrated Jsc from external quantum efficiency (EQE) spectrum shown in FIG. 3B reached 22.3 mA cm^"2, which is in good agreement with that from J- J⁷ measurement. Further increasing the ratio of TEOS to 10 vol% deteriorated the device performance. The photovoltaic parameters of these perovskite devices are summarized in Table 1. The statistics of Voc and PCE distributions shown in FIG. 3C and FIG. 3D demonstrate the reliability and repeatability of the Voc and PCE enhancement obtained by employing SiC -wrapped perovskite.

[0040j Table 1 Photovoltaic performance of perovskite (MAPbb) solar cells employing bare and SiC wrapped perovskite films.

| 0411 In order to provide further insight into the mechanisms for the performance enhancement induced by the S1O2 wrapping, the charge carrier transfer and photo-generated charge recombination lifetime were characterized by time-resolved photoluminescence (TRPL) decay and transient photovoltage (TPV) decay. As shown in FIG. 4A, the TRPL decay of the MAPbl3@Si02 film is much slower than that of bare MAPbb film, indicating slower carrier recombination in the silica-wrapped perovskite films. A charge recombination lifetime of 0.8 was deduced from TPV decay curves measured under one sun illumination for the

MAPbl3@Si02 based device, which was substantially longer than that (0.4 μβ) of the device with pristine, bare MAPbb, as illustrated in FIG. 4C. The longer charge recombination lifetime indicates the suppressed charge recombination at the film surface and/or grain boundaries, which was attributed to the well passivation of the S1O2 layer. The passivation effect of S1O2 was further verified by measuring the trap density of the devices with and without S1O2 wrapping. The variation of charge trap density in the MAPbl3@Si02-based device was analyzed using thermal admittance spectroscopy (TAS) measurements. As shown in FIG. 4C, there was a relatively large density of charge trap states, on the order of 10¹⁷ to 10¹⁸ m^"3 in the device with conventional perovskite layer. The tDOS of traps with an energy depth of 0.33-0.45 eV decreased by one to two orders of magnitude after wrapping perovskite grains with Si0₂ layers.

[0042] In order to study the stability of the silica-wrapped perovskite, all the films and devices were exposed to ambient environment without further encapsulation. After storing in air for 10 days, the impurity peak which is indexed to Pbl₂ appeared in the XRD pattern of bare MAPbb (see, FIG. 5A). In striking contrast, no impurity peak was identified in the XRD pattern of MAPbl3@Si0₂ even after exposure to air for 60 days. The performance of the perovskite device employing conventional perovskite degraded rapidly as shown in FIG. 5B. In

comparison, the efficiency of the device made of silica-coated perovskite (FIG. 5B) maintained nearly 90% of its original efficiency after 53 days.

[0043 J In one particular embodiment, a perovskite material of the form FAi-xMAxPb(Ii-xBr_x)3 may be used. To study the versatility of the silica wrapping methodology, devices were fabricated using FAi-xMAxPb(Ii-xBr_x)3 with x = 0.15: FAo.85MAo.i5Pb(Io.85Bro.i5)3. An optimized device with FAo.85MAo.i5Pb(Io.85Bro.i5)3@Si0₂ delivered an efficiency of 21.5% shown in FIG.

6A. The integrated Jsc from external quantum efficiency {/:Υ λ'. ) spectrum shown in FIG, 6B reached 22.9 mA cm^"2, which is in good agreement with that from J- V measurement. The steady-state photocurrent and effici ency measured at the maximum power point (1 .00 V) are presented in FIG. 6C, which confirms the devi ce performance parameters (Table 2) extracted from the J-V curve and verifies the absence of photocurrent hysteresis in these devices.

[0044J Table 2 Photovoltaic performance of perovskite (FAo.85MAo.i5Pb(Io.85Bro.i5)3) solar cells employing bare and Si0₂ wrapped perovskite films.

[0045] To assess the long-term operational stability of FAo.85MAo.i5Pb(Io.85Bro.i5)3@Si0₂ solar cells, a device was placed under continuous one sun illumination with a reference

MAPbl3@Si0₂ device. The devices were kept at a temperature of 80 °C for accelerated degradation study. As shown in the FIG. 7, all devices exhibited a fast degradation over the first 100 hours (h), with the MAPbl3@Si02 cell degrading to below 7% within 400 h. In contrast, the

FAo.85MAo.i5Pb(Io.85Bro.i5)3@Si02 cell only degraded by a few percent absolute efficiency over the first 100 h and then proceed to degrade at. a much slower linear rate.

[0046] In certain aspects, the silica shell coated on the perovskite grains should be within about 1-10 nm in thickness so as to not disadvantageously impact the charge transport property of the perovskite.

[0047] In certain embodiments, the general chemical structure of the silica precursors is Rn- Si-(OR)4-n, where "R" is an alkyl, aryl, or organofunctional group, and "OR" is a methoxy, ethoxy, or acetoxy group. Example silica shell precursors include tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), Tetrapropyl orthosilicate , organoalkoxysilanes, 3- (trimethoxysilyl)propylmethacrylate (TMSPMA), 3-glycidoxypropyltrimethoxysilane

(GLYMO), methyltrimethoxysilane (MTMOS), (3-Glycidyloxypropyl)trimethoxysilane, (3- Mercaptopropy)trimethoxysilane, (3-Glycidyloxypropyl)trimethoxysilane, N-[3- (Trimethoxysilyl)propyl]ethylenediamine, 3-Aminopropyl(diethoxy)methylsilane, [3-(2- Aminoethylamino)propyl]trimethoxysilane, 3-(Trimethoxysilyl)propyl methacrylate,

Triacetoxy(methyl)silane, (3-Aminopropyl)tris(trimethylsiloxy)silane, Triacetoxy(vinyl)silane, Tris(2-methoxyethoxy)(vinyl)silane, Silicon tetraacetate, Mpeg5K-Silane, Triethoxy(4- methoxyphenyl)silane, Cyanom ethyl [3-(trimethoxysilyl)propyl] trithiocarbonate, and

Trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane.

[0048] In certain device embodiments, a first carrier transport layer (e.g., ETM layer) is disposed between the active layer (e.g., perovskite@silica layer) and the cathode, and a second carrier transport layer (e.g., HTM layer) is disposed between the active layer and the anode, the first carrier transport layer having a higher electron conductivity than the second carrier transport layer, the second carrier transport layer having a higher hole conductivity than the first carrier transport layer.

[0049] In certain embodiments, the first carrier transport layer comprises at least one of C₆o, a fullerene, a fullerene-derivative, LiF, CsF, L1C0O2, Cs2cCb, TiOx, T1O2 nanorods (NRs), ZnO, ZnO nanorods (NRs), ZnO nanoparticles (NPs), ZnO, AI2O3, CaO, bathocuproine (BCP), copper phthalocyanine (CuPc), pentacene, pyronin B, pentadecafluorooctyl phenyl-C60-butyrate (F- PCBM), C60, C60/UF, ZnO Rs/PCBM, ZnO/cross-linked fullerene derivative (C-PCBSD), single walled carbon nanotubes (SWCNT), graphene, poly(ethylene glycol) (PEG),

Polyethylenimine (PEI), poly(dimethylsiloxaneblock-methyl methacrylate) (PDMS-b-PMMA), polar polyfluorene (PF-EP), polyfluorene bearing lateral amino groups (PFN), polyfluorene bearing quaternary ammonium groups in the side chains (WPF-oxy-F), polyfluorene bearing quaternary ammonium groups in the side chains (WPF-6-oxy-F), fluorene alternating and random copolymer bearing cationic groups in the alkyl side chains (PFNBr-DBTI5), fluorene alternating and random copolymer bearing cationic groups in the alkyl side chains (PFP Br), or poly(ethylene oxide) (PEO).

[0050] In certain embodiments, the second carrier transport layer comprises at least one poly(3,4-ethylenedioxithiophene) (PEDOT) doped with poly(styrene sulfonicacid) (PSS), 4,4'bis[(ptrichlorosilylpropylphenyl)phenylamino]biphenyl (TPD-Si2), poly(3-hexyl-2,5- thienylene vinylene) (P3HTV) and C60, copper phthalocyanine (CuPc), poly[3,4- (lhydroxymethyl) ethyl enedioxythiophene] (PHEDOT), n-dodecylbenzenesulfonic

acid/hydrochloric acid-doped poly(aniline) nanotubes (a-PANIN)s, poly(styrenesulfonic acid)- graft-poly (aniline) (PS SA-g-PANI), poly[(9,9-dioctylfluorene)-co-N-(4-(l- methylpropyl)phenyl)diphenylamine] (PFT), 4,4'bis[(p-trichlorosilylpropylphenyl)phenylamino] biphenyl (TSPP), 5,5'-bis[(p-trichlorosilylpropylphenyl) phenylamino]-2,20-bithiophene (TSPT), N-propyltriethoxysilane, 3,3,3-trifluoropropyltrichlorosilane or 3- aminopropyltriethoxysilanePoly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), V205, VOx, Mo03, W03, Re03, NiOx, ABO2 (A and B are metal cations, e.g. CuA10₂, CuGaC ), AgOx/PEDOT:PSS, Cu20, CuSCN/P3HT, or Au nanoparticles.

[0051] In certain embodiments, the anode layer includes at least one of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony -tin mixed oxide (ATO), a conductive polymer, a network of metal nanowire, a network of carbon nanowire, nanotube, nanosheet, nanorod, carbon nanotube, silver nanowire, or graphene.

[0052] In certain embodiments, the cathode layer includes at least one of copper, aluminum, calcium, magnesium, lithium, sodium, potassium, strontium, cesium, barium, iron, cobalt, nickel, silver, zinc, tin, samarium, ytterbium, chromium, gold, graphene, an alkali metal fluoride, an alkaline-earth metal fluoride, an alkali metal chloride, an alkaline-earth metal chloride, an alkali metal oxide, an alkaline-earth metal oxide, a metal carbonate, a metal acetate, or a combination of at least two of the above materials.

[0053] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. |0G54] The use of the terms "a" and "an" and "the" and "at least one" and similar referents in the context of describing the disclosed subject matter (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term "at least one" followed by a list of one or more items (for example, "at least one of A and B") is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms

"comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or example language (e.g., "such as") provided herein, is intended merely to better illuminate the disclosed subject matter and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

|0055) Certain embodiments are described herein. Variations of those embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the embodiments to be practiced otherwise than as specifically described herein.

Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

CLAIM(S):

1. A method of forming a perovskite layer, the method comprising:

mixing a perovskite solution with a silica shell precursor solution to produce a perovskite-silica precursor solution; and

spin casting or drop casting the perovskite-silica precursor solution on a substrate to form a perovskite layer, wherein the perovskite layer includes a plurality of groups of one or more perovskite grains, each of said plurality of groups wrapped in a silica shell.

2. The method of claim 1, wherein the silica shell precursor solution has a chemical structure of Rn-Si-(OR)4-n, where "R" is an alkyl, aryl, or organofunctional group, and "OR" is a methoxy, ethoxy, or acetoxy group.

3. The method of claim 1, wherein the silica shell precursor is selected from the group consisting of tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), Tetrapropyl orthosilicate , organoalkoxysilanes, 3-(trimethoxysilyl)propylmethacrylate (TMSPMA), 3- glycidoxypropyltrimethoxysilane (GLYMO), methyltrimethoxysilane (MTMOS), (3- Glycidyloxypropyl)trimethoxysilane, (3-Mercaptopropy)trimethoxysilane, (3- Glycidyloxypropyl)trimethoxysilane, N-[3-(Trimethoxysilyl)propyl]ethylenediamine, 3- Aminopropyl(diethoxy)methylsilane, [3-(2-Aminoethylamino)propyl]trimethoxysilane, 3- (Trimethoxysilyl)propyl methacrylate, Triacetoxy(methyl)silane, (3- Aminopropyl)tris(trimethylsiloxy)silane, Triacetoxy(vinyl)silane, Tris(2- methoxyethoxy)(vinyl)silane, Silicon tetraacetate, Mpeg5K-Silane, Triethoxy(4- methoxyphenyl)silane, Cyanom ethyl [3-(trimethoxysilyl)propyl] trithiocarbonate, and

Trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane.

4. The method of claim 1, wherein the perovskite precursor solution comprises MAI and Pbl₂.

5. The method of claim 4, wherein the perovskite grains comprise MAPBI3.

6. The method of claim 1, wherein the perovskite grains comprise FAi-_xMA_xPb(Ii- xBr_x)3.

7. The method of claim 1, wherein the perovskite grains comprise organometal trihalide perovskite having the formula ABX₃, or A2BX4, wherein A is methylammonium (CH₃ H₃ ⁺), formamidinium (H2NCHNH₂ ⁺), or an alkali-metal ion , B is a metal cation, and X is a halide anion, thiocyanate (SCN-) or a mixture thereof.

8. The method of any of claims 1 to 7, wherein each silica shell is between about 1 nm and about 10 nm in thickness.

9. A semiconductor device, comprising:

a cathode layer;

an anode layer;

an active layer disposed between the cathode layer and the anode layer, wherein the active layer includes a perovskite layer, wherein the perovskite layer includes a plurality of groups of one or more perovskite grains, each of said plurality of groups wrapped in a silica shell.

10. The semiconductor device of claim 9, wherein the perovskite layer includes organometal trihalide perovskite having the formula ABX₃, or A2BX4, wherein A is

methylammonium (CH₃ H₃ ⁺), formamidinium (H2NCHNH2⁺), or an alkali-metal ion , B is a metal cation, and X is a halide anion, thiocyanate (SCN^") or a mixture thereof.

11. The semiconductor device of claim 9, further comprising:

a first carrier transport layer disposed between the active layer and the cathode; and a second carrier transport layer disposed between the active layer and the anode, the first carrier transport layer having a higher electron conductivity than the second carrier transport layer, the second carrier transport layer having a higher hole conductivity than the first carrier transport layer.

12. The semiconductor device of claim 11, wherein:

the first carrier transport layer comprises at least one C60, a fullerene, a fullerene- derivative, LiF, CsF, L1C0O2, CS2c0₃, TiOx, T1O2 nanorods (NRs), ZnO, ZnO nanorods (NRs), ZnO nanoparticles (NPs), ZnO, Ah0₃, CaO, bathocuproine (BCP), copper phthalocyanine (CuPc), pentacene, pyronin B, pentadecafluorooctyl phenyl-C60-butyrate (F-PCBM), C60, C60/UF, ZnO Rs/PCBM, ZnO/cross-linked fullerene derivative (C-PCBSD), single walled carbon nanotubes (SWCNT), graphene, poly(ethylene glycol) (PEG), Polyethylenimine (PEI), poly(dimethylsiloxaneblock-methyl methacrylate) (PDMS-b-PMMA), polar polyfluorene (PF- EP), polyfluorene bearing lateral amino groups (PFN), polyfluorene bearing quaternary ammonium groups in the side chains (WPF-oxy-F), polyfluorene bearing quaternary ammonium groups in the side chains (WPF-6-oxy-F), fluorene alternating and random copolymer bearing cationic groups in the alkyl side chains (PF Br-DBTI5), fluorene alternating and random copolymer bearing cationic groups in the alkyl side chains (PFP Br), or poly(ethylene oxide) (PEO); and

the second carrier transport layer comprises at least one poly(3,4-ethylenedioxithiophene) (PEDOT) doped with poly(styrene sulfonicacid) (PSS),

4,4'bis[(ptrichlorosilylpropylphenyl)phenylamino]biphenyl (TPD-Si2), poly(3-hexyl-2,5- thienylene vinylene) (P3HTV) and C60, copper phthalocyanine (CuPc), poly[3,4- (lhydroxymethyl) ethylenedioxythiophene] (PHEDOT), n-dodecylbenzenesulfonic

acid/hydrochloric acid-doped poly(aniline) nanotubes (a-PANIN)s, poly(styrenesulfonic acid)- graft-poly (aniline) (PS SA-g-PANI), poly[(9,9-dioctylfluorene)-co-N-(4-(l- methylpropyl)phenyl)diphenylamine] (PFT), 4,4'bis[(p-trichlorosilylpropylphenyl)phenylamino] biphenyl (TSPP), 5,5'-bis[(p-trichlorosilylpropylphenyl) phenylamino]-2,20-bithiophene (TSPT), N-propyltriethoxysilane, 3,3,3-trifluoropropyltrichlorosilane or 3- aminopropyltriethoxysilanePoly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), V2O5, VOx, M0O3, WO3, ReC-3, NiOx, AgOx/PEDOT:PSS, Cu₂0, ABO2, wherein A and B are metal cations, CuAlC , CuGa0₂, CuSCN/P3HT, or Au nanoparticles.

13. The semiconductor device of claim 9, wherein the anode layer includes at least one of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony-tin mixed oxide (ATO), a conductive polymer, a network of metal nanowire, a network of carbon nanowire, nanotube, nanosheet, nanorod, carbon nanotube, silver nanowire, or graphene.

14. The semiconductor device of claim 9, wherein the cathode layer includes at least one of copper, aluminum, calcium, magnesium, lithium, sodium, potassium, strontium, cesium, barium, iron, cobalt, nickel, silver, zinc, tin, samarium, ytterbium, chromium, gold, graphene, an alkali metal fluoride, an alkaline-earth metal fluoride, an alkali metal chloride, an alkaline-earth metal chloride, an alkali metal oxide, an alkaline-earth metal oxide, a metal carbonate, a metal acetate, or a combination of at least two of the above materials.