HK1163343A - Enhancement of organic photovoltaic cell open circuit voltage using electron/hole blocking exciton blocking layers - Google Patents

Description

Enhancement of organic photovoltaic cell open circuit voltage using electron/hole blocking exciton blocking layers

Cross Reference to Related Applications

This application claims priority to U.S. provisional application 61/144,043 filed on 12.1.2009, which is incorporated herein by reference in its entirety.

Declaration of federally sponsored research

This invention was made with U.S. government support under FA9550-07-1-0364 awarded by the U.S. air force scientific research institute and DE-FG36-08GO18022 awarded by the U.S. department of energy. The government has certain rights in the invention.

Joint research protocol

In accordance with the joint university-corporation scientific agreement, the claimed invention is made by, on behalf of, and/or in conjunction with one or more of the following: university of michigan and Global Photonic Energy Corporation (Global Photonic Energy Corporation). This protocol was effective on and before the date the invention was made, and the claimed invention was made as a result of actions taken within the scope of this protocol.

Technical Field

The present invention generally relates to photosensitive optoelectronic devices comprising at least one blocking layer selected from the group consisting of electron blocking layers and hole blocking layers. The present invention also relates to methods of using at least one blocking layer as described herein to improve power conversion efficiency in photosensitive optoelectronic devices. The electron blocking layer and the hole blocking layer of the disclosed device may be used to reduce dark current and increase open circuit voltage.

Background

Optoelectronic devices rely on the optical and electronic properties of materials to electronically generate or detect electromagnetic radiation, or to generate electricity from ambient electromagnetic radiation.

Photosensitive optoelectronic devices convert electromagnetic radiation into electricity. Solar cells, also known as Photovoltaic (PV) devices, are a type of photosensitive optoelectronic device that is used exclusively for generating electrical power. PV devices that can generate electrical energy from light sources other than sunlight can be used to drive power consuming loads, to provide, for example, lighting, heating, or to provide power to electronic circuits or devices such as calculators, radios, computers, or remote monitoring or communication equipment. These power generation applications also typically involve charging batteries or other energy storage devices when direct illumination from the sun or other light source is not available so that operation can continue or be used to balance the power output of the PV device for the needs of a particular application. The term "resistive load" as used herein refers to any circuit, device, apparatus, or system that consumes power or stores power.

Another type of photosensitive optoelectronic device is a photoconductive cell. In this function, the signal detection circuit monitors the resistance of the device, thereby detecting changes due to light absorption.

Another type of photosensitive optoelectronic device is a photodetector. In operation, a photodetector is used in conjunction with a current detection circuit that measures the current generated when the photodetector is exposed to electromagnetic radiation and may have an applied bias voltage. The detection circuit described herein is capable of providing a bias voltage to a photodetector and measuring the electronic response of the photodetector to electromagnetic radiation.

These three types of photosensitive optoelectronic devices can be characterized according to whether a rectifying function is present as defined below and also according to whether the device operates with an externally applied voltage, also referred to as a bias voltage or bias voltage. The photoconductive cell has no rectifying function and is usually operated under a bias voltage. The PV device has at least one rectifying function and operates without a bias voltage. The photodetector has at least one rectifying function and is typically, but not always, operated at a bias voltage. As a general rule, a photovoltaic cell provides power to a circuit, device or apparatus, but does not provide a signal or current to control the detection circuit, or the output of information from the detection circuit. In contrast, a photodetector or photoconductor provides a signal or current to control the detection circuit, or the output of information from the detection circuit, but does not provide power to the circuit, device or apparatus.

Conventionally, photosensitive optoelectronic devices are constructed from a large number of inorganic semiconductors, such as crystalline, polycrystalline and amorphous silicon, gallium arsenide, cadmium telluride, and others. The term "semiconductor" herein denotes a material capable of conducting electricity when charge carriers are induced by thermal or electromagnetic excitation. The term "photoconduction" generally refers to a process in which electromagnetic radiation energy is absorbed and thus converted into excitation energy of charge carriers, such that the carriers are capable of conducting, i.e., transporting, charges in a material. The terms "photoconductor" and "photoconductive material" are used herein to refer to semiconductor materials that are selected for their property of absorbing electromagnetic radiation to generate charge carriers.

PV devices can be characterized in terms of their efficiency in converting incident solar power to useful electrical power. Devices utilizing crystalline or amorphous silicon dominate commercial applications, and some have achieved efficiencies of 23% or greater. However, the production of efficient crystal-based devices, particularly large surface area devices, is difficult and expensive due to the problems inherent in producing large crystals that do not contain significant efficiency-reducing defects. On the other hand, high-efficiency amorphous silicon devices still have problems in terms of stability. The stable efficiency of currently commercially available amorphous silicon cells is between 4% and 8%. Recent efforts have focused on the use of organic photovoltaic cells to achieve acceptable photovoltaic conversion efficiency through economical production costs.

Can be under standard lighting conditions (i.e., 1000W/m)²Standard test conditions for AM1.5 spectral illumination) to obtain maximum electrical power generation to obtain maximum product of photocurrent and photovoltage. The power conversion efficiency of such a battery under standard lighting conditions depends on three parameters: (1) current at zero bias, i.e. short-circuit current I_SCAmperometric, (2) photovoltage under open circuit conditions, i.e. open circuit voltage V_OCIn volts, and (3) a fill factor ff.

When a PV device is connected across a load and illuminated by light, it produces a photo-generated current. When a PV device is illuminated under an infinite load, it generates its maximum possible voltage V_{Open circuit}Or V_OC. When the PV device is illuminated in the event of a short circuit of the electrical contacts, it generates its maximum possible current I_{Short circuit}Or I_SC. When a PV device is actually used to generate power, it is connected to a finite resistive load and the power output is given by the product of the current and the voltage I × V. The maximum total power generated by a PV device cannot inherently exceed the product I_SC×V_OC. When the load value is optimized for maximum power extraction, the current and voltage each have a value of I_maxAnd V_max。

The figure of merit of a PV device is the fill factor, ff, which is defined as follows:

ff＝{I_maxV_max}/{I_SCV_OC}

where ff is always less than 1, since I can never be obtained simultaneously in practical use_SCAnd V_OC. Nonetheless, the closer ff is to 1, the smaller the series or internal resistance of the device and, therefore, the best conditions to deliver I to the load_SCAnd V_OCA greater percentage of the product of (a). Wherein, P_incIs the power incident on the device, the power efficiency of the device eta_pCan be calculated by the following formula:

η_p＝ff*(I_SC*V_OC)/P_inc

when electromagnetic radiation of appropriate energy is incident on a semiconducting organic material, for example an Organic Molecular Crystal (OMC) material or a polymer, photons can be absorbed, thereby producing an excited molecular state. This is symbolized as. Here S₀And S₀ ^*Representing the ground state and excited molecular state, respectively. The energy absorption and electrons are transferred from a bound state at the Highest Occupied Molecular Orbital (HOMO) level, which may be the B band, to a bound state at the Highest Occupied Molecular Orbital (HOMO) level, which may be the B band^*The elevation of the Lowest Unoccupied Molecular Orbital (LUMO) level of the band, or equivalently, the elevation of holes from the LUMO level to the HOMO level. In organic thin film photoconductors, the generated molecular state is generally considered to be an exciton, i.e. an electron-hole pair in a bound state which is transported as a quasi-particle. Excitons may have a considerable lifetime before they recombine pairwise, which refers to the process by which an initial electron and hole recombine with each other, as opposed to the recombination of holes or electrons from other pairs. To generate a photocurrent, electron-hole pairs are typically separated at the donor-acceptor interface between two different contacting organic thin films. If the charges are not separated, they can recombine, also known as quenching, in pairwise recombination, either by emitting light radiation of lower energy than the incident light or non-radiatively by generating heat. In photosensitive optoelectronic devices, either of these results is undesirable.

The electric field or inhomogeneity at the contact may cause the exciton to quench rather than dissociate at the donor-acceptor interface, resulting in no contribution to the current. It is therefore desirable to keep photogenerated excitons away from contact. This has the effect of limiting the diffusion of excitons to regions near the junction so that the associated electric field is more likely to separate charge carriers released by dissociation of excitons near the junction.

In order to generate an internally generated electric field occupying a considerable volume, it is common practice to juxtapose two layers of material having appropriately chosen conductivity properties, in particular taking into account their distribution of molecular quantum energy states. The interface of the two materials is known as a photovoltaic heterojunction. In conventional semiconductor theory, the materials used to form PV heterojunctions have been commonly denoted as n-or p-type. Where n-type means that the majority carrier type is electron. This can be viewed as a material having many electrons in relatively free energy states. P-type means that the majority carrier type is holes. This material has many holes in relatively free energy states. The type of background, i.e. the non-photogenerated majority carrier concentration, depends mainly on the unintentional doping of defects or impurities. The type and concentration of impurities determine the value of the fermi energy or energy level in the gap between the Highest Occupied Molecular Orbital (HOMO) level and the Lowest Unoccupied Molecular Orbital (LUMO) level, called the HOMO-LUMO gap. Fermi energy characterizes the statistical occupancy of molecular quantum states represented by energy values for which the probability of occupancy equals 1/2. The fermi energy near the LUMO energy level indicates that electrons are the predominant carrier. The fermi energy near the HOMO level indicates that holes are the predominant carrier. Hence, fermi energy is a major characteristic attribute of conventional semiconductors, and the prototype PV heterojunction is traditionally a p-n interface.

Therein, the term "rectifying" means especially that the interface has asymmetric conductive properties, i.e. the interface supports electron charges that are preferably transported in one direction. Rectification is typically associated with a built-in electric field occurring at the heterojunction between appropriately selected materials.

As used herein, and as is generally understood by those skilled in the art, a first "Highest Occupied Molecular Orbital (HOMO)" or "Lowest Unoccupied Molecular Orbital (LUMO)" energy level is greater than or "higher than" a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Because the Ionization Potential (IP) is measured as negative energy relative to the vacuum level, a higher HOMO energy level corresponds to an IP with a smaller absolute value (less negative IP). Similarly, a higher LUMO energy level corresponds to an Electron Affinity (EA) with a smaller absolute value (EA) to a lesser extent. On a conventional energy level diagram, with the vacuum level at the top, the LUMO level of a material is higher than the HOMO level of the same material. The "higher" HOMO or LUMO energy level is closer to the top of the figure than the "lower" HOMO or LUMO energy level.

In the case of organic materials, the terms "donor" and "acceptor" refer to the relative positions of the HOMO and LUMO energy levels of two contacting but different organic materials. This is in contrast to the use of these terms in the case of inorganic materials, in which case "donor" and "acceptor" may refer to the types of dopants that may be used to create inorganic n-type and p-type layers, respectively. In the organic case, a material is an acceptor if the LUMO level of the material in contact with another material is low. Otherwise it is a donor. Without an external bias, it is energetically advantageous for electrons at the donor-acceptor junction to move into the acceptor material and for holes to move into the donor material.

An important property of organic semiconductors is carrier mobility. Mobility measures the ease with which charge carriers can move through a conductive material in response to an electric field. In the case of organic photosensitive devices, a layer comprising a material that conducts preferentially by electrons due to high electron mobility is referred to as an electron transport layer or ETL. A layer comprising a material that conducts preferentially by holes due to high hole mobility is called a hole transport layer or HTL. Preferably, but not necessarily, the acceptor material is an ETL and the donor material is an HTL.

Conventional inorganic semiconductor PV cells employ a p-n junction to create an internal field. Early organic thin film batteries included heterojunctions similar to those employed in conventional inorganic PV cells, as reported, for example, by Tang, appl. phys lett.48, 183 (1986). However, it is now recognized that in addition to the establishment of p-n type junctions, energy level compensation of the heterojunction plays an important role.

Due to the fundamental nature of the photo-generation process in organic materials, energy level compensation at the organic D-a heterojunction is considered important for the operation of organic PV devices. When the organic material is photoexcited, local frenkel excitons or charge transfer excitons may be generated. In order for electrical detection or current generation to occur, the bound excitons must be dissociated into their component electrons and holes. This process can be induced by built-in electric fields, but the efficiency of the electric field obtained in organic devices is generally low (F10)⁶V/cm). The most efficient exciton dissociation in organic materials occurs at the donor-acceptor (D-a) interface. At the interface, a donor material having a low ionization potential forms a heterojunction with an acceptor material having a high electron affinity. Depending on the arrangement of the energy levels of the donor and acceptor materials, dissociation of the exciton at this interface can become energetically favorable, resulting in a free electron polaron in the acceptor material and a free hole polaron in the donor material.

Organic PV cells have many possible advantages when compared to conventional silicon-based devices. Organic PV cells are lightweight, economical in material usage, and can be deposited on low cost substrates such as flexible plastic foils. However, organic PV devices typically have relatively low external quantum efficiencies (conversion efficiency of electromagnetic radiation to electricity), on the order of 1% or less. This is partly believed to be due to the second order nature of the inherent light guiding process. That is, carrier generation requires exciton generation, diffusion, and ionization or aggregation. There is an efficiency η associated with each of these processes. The subscripts may be used as follows: p for power efficiency, EXT for external quantum efficiency, a for photon absorption, ED for diffusion, CC for concentration, and INT for internal quantum efficiency. Using this annotation:

η_p～η_EXT＝η_A*η_ED*η_CC

η_EXT＝η_A*η_INT

diffusion length (L) of excitons_D) Is typically much smaller (L) than the light absorption length (500 Delta)_D50 delta) a compromise is required between using a thick and therefore resistive cell with multiple or highly folded interfaces or using a thin cell with low light absorption efficiency.

The power conversion efficiency can be expressed asWherein V_OCIs the open circuit voltage, FF is the fill factor, J_SCIs a short-circuit current, and P₀Is the input optical power. Improved eta_pBy way of V_OCIn most organic PV cells, V_OCStill 3-4 times less than the typical absorbed photon energy. At dark current and V_OCThe relationship between can be derived from:

wherein J is the total current, J_SIs reverse dark saturation current, n is an ideality factor, R_SIs a series resistance, R_pIs a parallel resistance, V is a bias voltage, and J_phIs the photocurrent (Rand et al, Phys. Rev. B, vol 75, 115327 (2007)). Setting J to 0:

when J is_ph/J_SWhen > 1, V_OCAnd ln (J)_ph/J_S) In a ratio of (A) to (B),indicating a large dark current J_SResult in V_OCIs reduced.

As described herein, high dark currents in PV cells can result in a significant reduction in their power conversion efficiency. Dark current in an organic PV cell can come from several sources. Under forward bias, the dark current consists of: (1) generation/recombination current I due to electron-hole recombination at the donor/acceptor interface_gr(2) electron leakage current I due to electrons from the active donor-acceptor region of the cell to the anode, but not from an external source_eAnd (3) hole leakage current I due to holes formed in the donor-acceptor region of the cell moving to the cathode_h. Fig. 2 shows various components of dark current and associated energy levels. The magnitude of these current components depends to a large extent on the energy level. I is_grIncreases with decreasing donor-acceptor interface energy gap, which is the difference (Δ E) between the Lowest Unoccupied Molecular Orbital (LUMO) of the acceptor and the Highest Occupied Molecular Orbital (HOMO) of the donor_g)。I_eWith Delta E_LIs decreased and increased, Δ E_LIs the difference in the Lowest Unoccupied Molecular Orbital (LUMO) energies of the donor and acceptor. I is_hWith Delta E_HIs decreased and increased, Δ E_HIs the difference in the Highest Occupied Molecular Orbital (HOMO) energies of the donor and acceptor. Depending on the energy levels of the donor and acceptor materials, any of these three current components can become the dominant dark current.

For example, in tin phthalocyanine (SnPC)/C₆₀In PV cells, Δ E_LIs 0.2 eV. The energy barrier for electrons from acceptor to donor is low, resulting in a predominant electron leakage current I in the dark case_e. In copper phthalocyanine (CuPc)/C₆₀In the battery,. DELTA.E_LIs 0.8eV, resulting in negligible electron leakage current I_eSo as to generate/recombine the current I_grBecomes the main dark current source. Due to the relatively large Δ E at the most commonly used donor/acceptor pair_HHole leakage current I_hAnd is typically small.

In small molecule organic materials, tin (II) phthalocyanine (SnPc) has shown significant absorption at wavelengths from λ 600nm to 900nm, while terminating at λ 1000 nm. In practice, approximately 50% of the total solar photon flux is in the red and Near Infrared (NIR) spectra at wavelengths from λ 600nm to 100 nm. However, long wavelength absorbing materials such as SnPc generally result in having a low V_OCThe battery of (1).A thick discontinuous layer of SnPc has been included in CuPc/C₆₀Between heterojunctions to extend the absorption spectral range of other short wavelength (λ < 700nm) sensing photovoltaic cells (Rand et al, appl. phys. lett., 87, 233508 (2005)). Alternatively, SnPc is formed between CuPc and C₆₀Islands of discontinuity between (island) to achieve long wavelength sensitivity (Yang et al, appl. phys. lett.92, 053310 (2008)). C has been reported to₇₀SnPc tandem cells (Inoue et al, j.crystal. growth, 298, 782-.

Exciton blocking layers that also function as electron blocking layers have been developed for use in polymer Bulk Heterojunction (BHJ) PV cells (Hains et al, appl.phys.lett., volume 92, 023504 (2008)). In polymer BHJ PV cells, a polymer blend of donor and acceptor materials is used as the active region. These blends may have regions of donor or acceptor material extending from one electrode to the other. Thus, through one type of polymer molecule, there may be electron or hole conduction paths between the electrodes.

In addition to the polymer BHJ PV cell, when Δ E_LOr Δ E_HSmaller, other configurations, including planar PV devices, also exhibit significant electron or hole leakage current across the donor/acceptor heterojunction, even though these films may not have a single material (donor or acceptor) path between the two electrodes.

The present disclosure relates to increased power conversion efficiency of photosensitive optoelectronic devices through the use of electron blocking layers that block electrons and/or hole blocking layers that block holes. The invention also relates to dark current components of the PV cell and their correlation with the energy level alignment of the PV cell including the planar film. Methods of increasing the power conversion efficiency of photosensitive optoelectronic devices by using electron blocking layers and/or hole blocking layers are also disclosed.

Disclosure of Invention

The present disclosure relates to an organic photosensitive optoelectronic device comprising:

two electrodes comprising an anode and a cathode in overlapping relationship;

at least one donor material, and at least one acceptor material, wherein the donor material and acceptor material form a photosensitive region between the two electrodes;

at least one electron blocking layer or hole blocking layer between the two electrodes, wherein the electron blocking layer and the hole blocking layer comprise at least one material selected from an organic semiconductor, an inorganic semiconductor, a polymer, a metal oxide, or a combination thereof.

Non-limiting examples of electron blocking layers for use herein include those selected from tris (8-hydroxyquinoline) aluminum (III) (Alq3), N '-bis (3-methylphenyl) - (1, 1' -biphenyl) -4 '-diamine (TPD), 4' -bis [ N- (naphthyl) -N-phenylamino]Biphenyl (NPD), subphthalocyanine (SubPc), pentacene, squaric acid, copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), aluminum phthalocyanine chloride (ClAlPc), tris (2-phenylpyridine) (Ir (ppy)₃) ) at least one organic semiconductor material.

Non-limiting examples of the at least one metal oxide that may be used as the electron blocking layer include oxides of Cu, Al, Sn, Ni, W, Ti, Mg, In, Mo, Zn, and combinations thereof, such as NiO, MoO₃、CuAlO₂. Other inorganic materials that may be used as electron blocking layers include allotropes of carbon, such as diamond and carbon nanotubes, and MgTe.

Non-limiting examples of the at least one inorganic semiconductor material that may be used as the electron blocking layer include Si, II-VI semiconductor materials, and III-V semiconductor materials.

Non-limiting examples of the at least one hole blocking layer include at least one organic semiconductor material selected from naphthalene tetracarboxylic dianhydride (NTCDA), p-bis (triphenylsilyl) benzene (UGH2), 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA), and 7, 7, 8, 8-Tetracyanoterephthalquinodimethane (TCNQ).

The hole blocking layer may also include inorganic materials, non-limiting examples of which include TiO₂、GaN、ZnS、ZnO、ZnSe、SrTiO₃、KaTiO₃、BaTiO₃、MnTiO₃、PbO、WO₃And SnO₂。

The invention relates to an organic photosensitive optoelectronic device comprising: two electrodes comprising an anode and a cathode in overlapping relationship; at least one donor material, for example at least one material selected from CuPc, SnPc and squaric acid, and at least one acceptor material, for example C₆₀And/or PTCBI, wherein the donor material and acceptor material form a photosensitive region between the two electrodes; at least one electron blocking EBL or hole blocking EBL located between the two electrodes.

In one embodiment, an organic photosensitive optoelectronic device is disclosed wherein the at least one electron blocking EBL comprises a material selected from tris (8-hydroxyquinoline) aluminum (III) (Alq3), N '-bis (3-methylphenyl) - (1, 1' -biphenyl) -4 '-diamine (TPD), 4' -bis [ N- (naphthyl) -N-phenylamino ] s]Biphenyl (NPD), subphthalocyanine (SubPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), aluminum phthalocyanine chloride (ClAlPc), tris (2-phenylpyridine) iridium (Ir (ppy)₃) And MoO₃And the at least one hole blocking EBL includes at least one material selected from naphthalene tetracarboxylic dianhydride (NTCDA), p-bis (triphenylsilyl) benzene (UGH2), 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA), and 7, 7, 8, 8-Tetracyanoterephthalquinodimethane (TCNQ).

In view of the location of the disclosed blocking layer, an electron blocking EBL may be adjacent to the donor region and a hole blocking EBL may be adjacent to the acceptor region. It is also understood that devices can be fabricated that include both electron blocking EBLs and hole blocking EBLs.

In one embodiment, the first photoconductive organic semiconductor material and the second photoconductive organic semiconductor material are selected to be spectrally sensitive in the visible spectrum. It is understood that the first photoconductive organic semiconductor material and the second photoconductive organic semiconductor material may be at least partially mixed.

In one embodiment, the donor region comprises at least one material selected from CuPc and SnPc, and the acceptor region comprises C₆₀And the electron blocking EBL comprises MoO₃。

The devices described herein may be organic photodetectors or organic solar cells.

The present invention also relates to a stacked organic photosensitive optoelectronic device comprising a plurality of photosensitive optoelectronic subcells, wherein at least one subcell comprises: two electrodes comprising an anode and a cathode in overlapping relationship; at least one donor material, for example at least one material selected from CuPc, SnPc and squaric acid, and at least one acceptor material, for example C₆₀And/or PTCBI, wherein the donor material and acceptor material form a photosensitive region between the two electrodes; at least one electron blocking EBL or hole blocking EBL located between the two electrodes.

As described above, in the stacked organic photosensitive devices described herein, the at least one electron blocking EBL comprises a material selected from the group consisting of tris (8-hydroxyquinoline) aluminum (III) (Alq3), N '-bis (3-methylphenyl) - (1, 1' -biphenyl) -4 '-diamine (TPD), 4' -bis [ N- (naphthyl) -N-phenylamino]Biphenyl (NPD), subphthalocyanine (SubPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), aluminum phthalocyanine chloride (ClAlPc), tris (2-phenylpyridine) (Ir (ppy)₃) And MoO₃And the at least one void isThe hole blocking EBL includes at least one material selected from naphthalene tetracarboxylic dianhydride (NTCDA), p-bis (triphenylsilyl) benzene (UGH2), 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA), and 7, 7, 8, 8-Tetracyanoterephthalquinodimethane (TCNQ).

The present invention also relates to a method of increasing the power conversion efficiency of a photosensitive optoelectronic device comprising including at least one of the electron blocking EBL and the hole blocking EBL described herein to reduce dark current and increase the open circuit voltage of the device.

In addition to the subject matter discussed above, the present invention includes a number of other exemplary features, such as those described below. It is to be understood that both the foregoing description and the following description are exemplary only.

Drawings

The accompanying drawings are incorporated in and constitute a part of this specification.

FIG. 1 shows ITO/SnPc under dark conditions and illumination levels of 0.2sun and 1sun, AM1.5 illumination/C₆₀/BCP(Al) Photovoltaic (PV) cell (open square) and ITO/CuPc/C₆₀/BCP/Al PVCurrent density vs. voltage characteristics of the battery (empty triangle). Dark current fitting results are also shown (solid line).

Fig. 2(a) and 2(b) show energy level diagrams of a bi-layer organic photovoltaic cell.

Fig. 3 shows a schematic energy level diagram showing the energy levels of (a) the structure of a Photovoltaic (PV) cell comprising an electron blocking EBL, and (b) the materials suitable for the electron blocking EBL in SnPc and squaric PV cells.

FIG. 4 shows a schematic energy level diagram showing (a) the structure of a Photovoltaic (PV) cell comprising a hole-blocking EBL, and (b) a photovoltaic cell adapted to be at C₆₀And the energy level of the material of the hole blocking EBL in the PTCBI PV cell.

FIG. 5 shows EBL without electron blocking (dashed line), with MoO₃Electron blocking EBL (open squares), ITO/SnPc with SubPc Electron blocking EBL (open triangles), and with CuPc Electron blocking EBL (open circles)/C₆₀/BCPThe current density vs. voltage characteristic of the/Al photovoltaic cell. The energy levels of the devices with electron blocking EBLs are illustrated in the inset. Photocurrent was measured under 1sun, AM1.5 illumination. Dark current fitting results are also shown (solid line).

FIG. 6 shows ITO/CuPc/C₆₀/BCP/AlPhotovoltaic (PV) cell, and no barrier layer, with MoO₃Electron blocking EBL, ITO/SnPc with SubPc and CuPc/C₆₀/BCPExternal Quantum Efficiency (EQE) vs. wavelength for/Al PV cells.

Detailed Description

As shown, the barrier layers described herein may include at least one organic or inorganic material. In either case, the requirements for the barrier layer are the same. Sometimes the only difference appears in the terminology used. For example, the energy levels of organic materials are generally described in the HOMO and LUMO levels, whereas in inorganic materials, the energy levels are generally described in the valence band (corresponding to the HOMO level) and the conduction band (corresponding to the LUMO level).

The present invention relates to photosensitive optoelectronic devices comprising at least one blocking layer, such as an electron blocking or hole blocking layer. It is understood that the electron blocking or hole blocking layer may also block excitons and thus function as an Exciton Blocking Layer (EBL). As used herein, the terms "electron blocking" or "hole blocking" may be used interchangeably individually or in combination with "EBL".

In one embodiment, the present invention relates to an organic photosensitive optoelectronic device comprising: two electrodes comprising an anode and a cathode in overlapping relationship; a donor region between the two electrodes, the donor region being formed of a first photoconductive organic semiconductor material; at the placeAn acceptor region between the two electrodes and adjacent to the donor region, the acceptor region being formed from a second photoconductive organic semiconductor material; at least one of an electron blocking EBL and a hole blocking HBL between the two electrodes and adjacent to at least one of the donor region and the acceptor region. By inserting electron blocking EBLs and/or hole blocking EBLs into the PV cell structure, cell dark current can be suppressed, leading to an accompanying V_OCIs increased. The power conversion efficiency of the PV cell can be improved.

It is understood that the present invention relates generally to the use of electron blocking EBLs and/or hole blocking EBLs in heterojunction PV cells. In at least one embodiment, the PV cell is a planar heterojunction cell. In another embodiment, the PV cell is a planar hybrid heterojunction cell. In other embodiments of the invention, the PV cell is non-planar. For example, the photoactive region may form at least one of a mixed heterojunction, a planar heterojunction, a bulk heterojunction, a nanocrystal-bulk heterojunction, and a hybrid planar mixed heterojunction.

The disclosed device includes two electrodes including an anode and a cathode. The electrodes or contacts are typically metals or "metal substitutes". The term metal is used herein to encompass materials composed of an elementally pure metal, such as Al, as well as metal alloys, which are materials composed of two or more elementally pure metals. Herein, the term "metal substitute" refers to a material that is not a metal within the ordinary definition, but that has the metal-like properties desired in the particular appropriate application. Metal alternatives commonly used for the electrodes and charge transport layers include doped wide bandgap semiconductors, e.g., transparent conducting oxides such as Indium Tin Oxide (ITO), Gallium Indium Tin Oxide (GITO), and Zinc Indium Tin Oxide (ZITO). Specifically, ITO is a highly doped degenerate n + semiconductor, having an optical bandgap of about 3.2eV, such that it has an optical bandgap of greater than aboutIs transparent.

Another suitable metal substitute material is the transparent conducting polymer Polyaniline (PANI) and its chemical relatives. The metal substitute may further be selected from a wide range of non-metallic materials, wherein the term "non-metallic" is intended to encompass a wide range of materials, provided that the material does not contain the metal in chemically unbound form. When a metal is present in an chemically unbound form, either alone or as an alloy with one or more other metals, the metal may alternatively be referred to as being present in its metallic form or as being "free metal". Thus, the metal substitute electrode of the present invention may sometimes be referred to as "metal-free," where the term "metal-free" is meant to encompass materials that do not contain the metal in chemically unbound form. Free metals are generally in the form of metallic bonds, which can be thought of as a chemical bond resulting from a large number of valence electrons throughout the metal lattice. Although metal substitutes may contain metal components, several essential components of them are "non-metals". They are not pure free metals, nor alloys of free metals. When metals are present in their metallic form, conductive strips tend to provide, among other metallic properties, high electrical conductivity and high reflectivity for light radiation.

The term "cathode" is used herein in the following manner. In a single unit of stacked PV devices or non-stacked PV devices, such as solar cells, electrons move from adjacent photoconductive materials to the cathode under ambient radiation, and in connection with a resistive load and in the absence of an externally applied voltage. Similarly, the term "anode" is used herein such that in a solar cell under illumination, holes move from the adjacent photoconductive material to the anode, which is equivalent to electrons moving in the opposite manner. Note that the terms anode and cathode as used herein may be electrodes or charge transport regions.

In at least one embodiment, the organic photosensitive optoelectronic device includes at least one photoactive region in which light is absorbed to form an excited state, or "exciton," which can subsequently be dissociated into electrons and holes. Dissociation of excitons typically occurs at a heterojunction formed by the juxtaposition of an acceptor layer and a donor layer, including a photoactive region.

Figure 2 shows an energy level diagram for a bi-layer donor/acceptor PV cell.

The first photoconductive organic semiconductor material and the second photoconductive organic semiconductor material may be selected to be spectrally sensitive in the visible spectrum.

The photoconductive organic semiconductor material according to the invention may comprise, for example, C₆₀4, 9, 10-perylenetetracarboxylic acid bis-benzimidazole (PTCBI), squaric acid, copper phthalocyanine (CuPc), tin phthalocyanine (SnPc), or boron subphthalocyanine (SubPc). Those skilled in the art will recognize other photoconductive organic semiconductor materials suitable for the present invention. In some embodiments, the first photoconductive organic semiconductor material and the second photoconductive organic semiconductor material are at least partially mixed to form a mixed heterojunction, a bulk heterojunction, a nanocrystal-bulk heterojunction, or a mixed planar mixed heterojunction or bulk heterojunction.

When the PV cell is operated under illumination, an output photocurrent is formed by the photo-generated electrons collected at the cathode and the photo-generated holes at the anode. Due to the induced potential drop and the electric field, dark current flows in opposite directions. Electrons and holes are injected from the cathode and anode, respectively, and can reach the opposite electrode if they do not encounter a large energy barrier. They can also recombine at the interface to form a composite current. Electrons and holes generated by heat in the active region can also contribute to dark current. Although this last component is dominant when the solar cell is reverse biased, it is negligible under forward bias conditions.

As mentioned, the dark current of an operating PV cell mainly originates from the following sources: (1) generation/recombination current I due to electron-hole recombination at the donor/acceptor interface_gr(2) due to electrons passing from the cathode to the anode through the donor/acceptor interfaceInduced electron leakage current I_eAnd (3) hole leakage current I due to holes from anode to cathode through the donor/acceptor interface_h. In operation, the solar cell has no externally applied bias. The magnitude of these current components depends on the energy level. I is_grEnergy gap with interface Delta E_gIs increased. I is_eWith Delta E_LIs decreased and increased, Δ E_LIs the difference in the Lowest Unoccupied Molecular Orbital (LUMO) energies of the donor and acceptor. I is_hWith Delta E_HIs decreased and increased, Δ E_HIs the difference in the Highest Occupied Molecular Orbital (HOMO) energies of the donor and acceptor. Depending on the energy levels of the donor and acceptor materials, any of these three current components can become the dominant dark current.

Electron blocking EBL

The electron blocking EBL according to an embodiment of the present invention may include an organic or inorganic material. In at least one embodiment, the electron blocking EBL is adjacent to the anode. In another embodiment, the polymer molecule may be used in a PV cell. For example, in one embodiment, the electron blocking EBL at the anode prevents the polymer molecules that make up the PV cell from contacting both electrodes. Thus, when used, the polymer making up the PV cell will not be in contact with both electrodes, which may eliminate the electron conduction path. In some embodiments of the invention, the battery has low dark current and high V_OC。

In one embodiment, the photoactive region forms at least one of a mixed heterojunction, a bulk heterojunction, a nanocrystal-bulk heterojunction, and a hybrid planar mixed heterojunction.

When electron leakage current I in PV cell_eWhen dominant, electron blocking layers can be used to reduce cell dark current and increase V_OC. Fig. 3(a) shows an energy level diagram of a structure including an electron blocking EBL. To effectively suppress electron leakage current I without affecting hole accumulation efficiency_eThe electron blocking EBL should satisfyThe standard is as follows:

1) the electron blocking EBL has a higher LUMO level than the donor material, for example at least 0.2eV higher.

2) The electron blocking EBL does not introduce a large energy barrier to hole accumulation at the electron blocking EBL/donor interface; and

3) the electron blocking EBL maintains a large interface gap at the interface with the donor material, as indicated by smaller generation/recombination currents than between the donor and acceptor, which may otherwise contribute significantly to the device dark current.

For example, SnPc has a LUMO energy of 3.8eV and a HOMO energy of 5.2eV at vacuum level. At SnPc/C₆₀Suitable electron blocking EBL materials of (a) may include, but are not limited to, tris (8-hydroxyquinoline) aluminum (III) (Alq3), N '-bis (3-methylphenyl) - (1, 1' -biphenyl) -4 '-diamine (TPD), 4' -bis [ N- (naphthyl) -N-phenylamino]Biphenyl (NPD), 4' -tris (N-3-methylphenyl-N-phenylamino) triphenylamine (MTDATA), subphthalocyanine (SubPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), aluminum phthalocyanine chloride (ClAlPc), tris (2-phenylpyridine) iridium (Ir (ppy)₃) And MoO₃. The energy levels of those materials are shown in fig. 3 (b).

Furthermore, for example, 2, 4-bis [4- (N, N-diisobutylamino) -2, 6-dihydroxyphenyl](squaric acid) has a LUMO energy of 3.7eV and a HOMO energy of 5.4 eV. The materials listed in FIG. 3(b) may also be included in the squaric acid/C₆₀The electrons in the cell block the EBL.

In some embodiments of the invention, the electron blocking EBL thickness ranges from aboutTo aboutFor example from aboutTo aboutOr even from aboutTo aboutIt is understood that in some embodiments, the electron blocking EBL thickness may range in accordance withIs increased fromTo about

Hole blocking EBL

In at least one embodiment of the present invention, the hole blocking EBL is adjacent to the acceptor region. Typically, due to the relatively large Δ E in the most common donor/acceptor pair_HHole leakage current I_hIs smaller. However, when in a PV cell, the hole leakage current I_hIs dominant, the hole blocking EBL can be used to reduce cell dark current and increase V_OC. An energy level diagram of a structure including the hole-blocking EBL according to the present invention is shown in fig. 4 (a). To effectively suppress the hole leakage current I without affecting the electron collecting efficiency_hThe hole blocking EBL should meet the following criteria:

1) the hole blocking EBL has a lower HOMO energy level than the acceptor material;

2) the hole blocking EBL does not introduce a large energy barrier to electron accumulation at the acceptor/hole blocking EBL interface, e.g., the LUMO of the blocking layer is about equal to or lower than the LUMO of the acceptor; and

3) the hole blocking EBL maintains a large interface gap at the interface with the acceptor material, as indicated by a smaller generation/recombination current than between the donor and acceptor, which may otherwise contribute significantly to the device dark current.

Acceptor materials according to the present invention include, but are not limited to, C₆₀And 4, 9, 10-perylenetetracarboxylic acid bisbenzimidazole (PTCBI). C₆₀And PTCBI both had a LUMO energy of 4.0eV and a HOMO energy of 6.2 eV.

According to the invention at C₆₀Or for hole blocking EBL in PTCBI cells include, but are not limited to, 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline (bathocuproine or BCP), naphthalene tetracarboxylic dianhydride (NTCDA), p-bis (triphenylsilyl) benzene (UGH2), 3, 4, 9, 10-perylene tetracarboxylic dianhydride (PTCDA), and 7, 7, 8, 8-Tetracyanoterephthalquinodimethane (TCNQ) (fig. 4 (b)). The LUMO level of the hole blocking EBL may be high, for example, if the cathode deposition introduces defect levels for electron transport. The hole-blocking EBL according to the present invention also functions as an exciton-blocking layer between the acceptor region and the cathode.

In some embodiments of the invention, the hole blocking EBL has a thickness ranging from aboutTo aboutFor example from aboutTo aboutOr even from aboutTo aboutIt is understood that in some embodiments, the range of hole blocking EBL thickness may be in accordance withIs increased fromTo about

The disclosed devices can provide significant power conversion efficiency increases. For example, ITO/tin (II) phthalocyanine (SnPc)/C₆₀Bathocuproine (BCP)/Al cell has high J due to high absorption coefficient in large spectral range_SCBut has low power conversion efficiency due to a low open circuit voltage. Thus at SnPc/C₆₀Use of electron blocking EBLs in a battery can increase V_OC. In some embodiments of the invention, the battery has low dark current and high V_OC. In some embodiments, V is blocked by using electron blocking EBL_OCMay be about 2 times larger. In other embodiments, V is achieved by using electron blocking EBL_OCCan be more than 2 times larger.

Stacked organic photosensitive optoelectronic devices are also contemplated herein. A stacked device according to the present invention may comprise a plurality of photosensitive optoelectronic subcells, wherein at least one subcell comprises: two cells comprising an anode and a cathode in overlapping relationship; a donor region between the two electrodes, the donor region being formed of a first photoconductive organic semiconductor material; an acceptor region between the two electrodes and adjacent to the donor region, the acceptor region being formed from a second photoconductive organic semiconductor material; and at least one of an electron blocking layer and a hole blocking layer between the two electrodes and adjacent to at least one of the donor region and the acceptor region. The stacked device may be constructed in accordance with the present invention to achieve high internal and external quantum efficiencies.

When the term "subcell" is used hereinafter, it refers to an organic photosensitive optoelectronic structure that may include at least one of an electron blocking EBL and a hole blocking EBL according to the present invention. When a subcell is used alone as a photosensitive optoelectronic device, it typically includes a complete set of electrodes, i.e., positive and negative. As disclosed herein, in some stacked configurations, adjacent subcells may utilize, i.e., share, a common electrode, charge transport region, or charge recombination zone. In other cases, adjacent subcells do not share a common electrode or charge transport region. The term "subcell" is disclosed herein to include subcell configurations, regardless of whether each subcell has its own unique electrode or shares an electrode or charge transport region with an adjacent subcell. The terms "battery", "subcell", "cell", "subcell", "component" and "subcomponent" are used interchangeably herein to refer to a photoconductive region or set of regions and an adjoining electrode or charge transport region. As used herein, the terms "stack," "stacked," "multi-component," and "multi-cell" refer to any optoelectronic device having multiple regions of photoconductive material separated by one or more electrodes or charge transport regions.

Because the stacked sub-cells of a solar cell may be fabricated using vacuum deposition techniques that allow external electrical connection to the electrodes of the separate sub-cells, each of the sub-cells in the device may be electrically connected in parallel or in series depending on whether the power and/or voltage generated by the PV cell is maximized. The improved external quantum efficiency that can be achieved for the stacked PV cell embodiments of the present invention can also be attributed to the fact that the sub-cells of the stacked PV cells can be electrically connected in parallel, since the parallel electrical configuration allows for a much higher fill factor to be achieved than when the sub-cells are connected in series.

In the case when the PV cell is comprised of sub-cells electrically connected in series to produce a higher voltage device, the stacked PV cell can be fabricated to have each sub-cell producing approximately the same current, thereby reducing inefficiencies. For example, if the incident radiation passes in only one direction, the stacked subcells may have an increased thickness where the outermost subcell most directly exposed to the incident radiation is the thinnest. Alternatively, if the sub-cells are made to overlap on the reflective surface, the thickness of the individual sub-cells may be adjusted to take into account the total combined radiation supplied to each sub-cell from the source and the reflective direction.

Furthermore, it is desirable to have a dc power supply capable of generating a large number of different voltages. For this application, external connections to the insertion electrode may have great utility. Thus, in addition to being able to provide the maximum voltage generated across the entire set of sub-cells, exemplary embodiments of the stacked PV cells of the present invention may also be used to provide multiple voltages from a single power source by tapping the selected voltage from a selected subset of sub-cells.

Representative embodiments of the present invention may also include transparent charge transport regions. As described herein, charge transport layers are distinguished from acceptor/donor regions/materials by the fact that charge transport regions are typically, but not necessarily, inorganic and they are generally selected to be not photoconductively active.

The organic photosensitive optoelectronic devices disclosed herein can be used in a wide variety of photovoltaic applications. In at least one embodiment, the device is an organic photodetector. In at least one embodiment, the device is an organic solar cell.

Examples

The present invention may be understood more readily by reference to the following detailed description of exemplary embodiments and working examples. It is understood that other embodiments will become apparent to those skilled in the art from consideration of the specification and practice disclosed herein.

Example 1

On a glass substrate coated beforehandThick ITO layer (15. omega./cm)²Sheet resistance of) a device. Placing the ITO surface cleaned by solvent on an ultraviolet/O (ultraviolet/oxygen) device₃ ^-Medium treatment for 5 minutes and then immediately loading it into a high-vacuum chamber (base pressure < 4X 10)^-7In a support), wherein organic layers are sequentially deposited by thermal evaporation andthick Al cathode. The deposition rate of the purified organic layer is(Laudise et al, J Crystal. growth, 187, 449 (1998)). An Al cathode was evaporated through a shadow mask having 1mm diameter openings to define the active area of the device. The current density vs. voltage (J-V) characteristics were measured under dark conditions and under simulated am1.5g solar illumination. Illumination intensity and quantum efficiency measurements were made using a standard method with a NREL calibrated Si detector (ASTM standards E1021, E948 and E973, 1998).

FIG. 1 shows ITO/SnPc/C60A copper bath (BCP,) Al PV cell, ITO/CuPc/C₆₀/BCPCurrent density-voltage (J-V) characteristics of/Al PV control, and dark J-V fitting results. SnPc-based devices have higher dark current compared to CuPc cells, which is understandable considering the difference in energy levels between the two structures. The Highest Occupied Molecular Orbital (HOMO) energy of SnPc and CuPc is 5.2eV at vacuum level (Kahn et al, J.Polymer Sci.B, 41, 2529-2548 (2003); Rand et al, Appl.Phys.Lett, 87, 233508 (2005)). The Lowest Unoccupied Molecular Orbital (LUMO) energy of CuPc was 3.2eV as measured by back-light electron spectroscopy (IPES). For SnPc, the LUMO energy estimated from the optical bandgap is 3.8 eV. Because of C₆₀The LUMO energy of (C) is 4.0eV (Shirley et al, Phys. Rev. Lett., 71(1), 133(1993)), so for CuPc/C₆₀Battery, this results in pair C₆₀Potential barrier of 0.8eV for electron transport from acceptor to anode, but for SnPc/C₆₀The device is only 0.2 eV. Thus, in CuPc/C₆₀Dark current in the battery mainly comes from CuPc/C₆₀Generation and recombination at the heterojunction, while at SnPc/C₆₀In the battery, electron leakage current from the cathode to the anode is dominant.

From equation (1), for SnPc-based cells, fitting to the dark J-V characteristic in fig. 1 yields n-1.5 and J_S＝5.1×10^-2mA/cm²And for a battery using CuPc as a donor, we find that n is 2.0 and J_S＝6.3×10^-4mA/cm². Hypothesis constant J_ph(V)＝J_SC(short-circuit current), V can be calculated using equation (2)_OC. Under 1sun illumination, neglecting small parallel resistance, V for SnPc_OC0.19V and for CuPc batteries V_OC0.46V. Fitting parameters and J from dark current_SCCalculated V_OCIn agreement with the measured values 0.16. + -. 0.01V and 0.46. + -. 0.01V, respectively.

Example 2

At SnPc/C₆₀In batteries, in order to reduce J_SAnd thus increase V_OCAn electron blocking EBL is interposed between the anode and the SnPc donor layer described in embodiment 1. According to the energy level diagram in the inset of fig. 2, the electron blocking EBL should (i) have a higher LUMO energy than the donor LUMO, (ii) have a relatively high hole mobility, and (iii) limit dark current due to generation and recombination at the interface with the donor due to the small electron blocking EBL (LUMO) to donor (LUMO) "interfacial gap" energy. In view of these considerations, the inorganic material MoO₃And subphthalocyanine boron chloride (SubPc) and CuPc are used as electron blocking EBLs (Mutolo et al, j.am.chem.soc, 128, 8108 (2006)). They all effectively block the electron current from the donor to the anode contact according to their respective energy levels (fig. 2). MoO has been previously used in polymer PV cells₃To prevent reaction between the ITO and the polymer PV active layer (Shrotriya et al, appl.phys.lett.88, 073508 (2006)).

By using electron blocking EBL for ITO/SnPc/C₆₀/BCPExperiments were performed in an/Al PV cell. FIG. 5 shows a liquid crystal display deviceThick MoO₃Electron blocking EBL,Thick SubPc EBL andthe CuPc electron of (2) blocks the J-V characteristic of the cell of the EBL. SnPc/C without barrier layer₆₀Is also characterized byShown for comparison. Electron blocking EBLs were found to suppress dark current significantly. V measured under 1sun illumination in all devices including electron blocking EBL_OCIncreasing to > 0.40V.

The properties of all devices are summarized in Table 1, and V is measured under 1sun standard AM1.5G solar illumination_OC、J_SCFill Factor (FF) and power conversion efficiency (eta)_p) The value of (c). High V_OCResulting in a concomitant increase in power conversion efficiency from (0.45 ± 0.1)% for SnPc devices without electron blocking EBL to a maximum (2.1 ± 0.1)% for SnPc devices with electron blocking EBL. Note that the SubPc electron blocking EBL introduces an energy barrier to holes other than electrons. It may therefore be made thicker than it is due to a small potential barrier (0.4eV, see inset of fig. 5) to hole conductionIncrease toResulting in a reduction of the fill factor and thus a slight reduction of the power conversion efficiency.

TABLE 1 Barrier/SnPc/C₆₀Performance of/BCP solar cells under 1sun AM1.5 illumination

Equation (1) is used to fit the dark current of all devices with the final fitting parameters listed in table 1. When MoO₃Layer thickness exceedingOr SubPc layer thickness >)When, J_SBut 1% of the device lacking the barrier layer. If it comes inOne step increase of electron blocking EBL thickness, then J_SThe additional reduction is small, indicating that these thin layers effectively eliminate electron leakage. As shown in Table 1, calculated V for all devices_OCThe values are consistent with the measured values.

FIG. 6 shows ITO/CuPc/C₆₀/BCP/AlPhotovoltaic (PV) cell, EBL without electron blocking layer, with MoO₃ITO/SnPc of Electron blocking EBL, with SubPc Electron blocking EBL, with CuPc Electron blocking EBL/C₆₀/BCPExternal Quantum Efficiency (EQE) spectra of/Al PV cells. The EQE value of CuPc cells decreases to < 10% at λ > 730nm, while the EQE value of all SnPc cells is > 10% at λ < 900 nm. By using MoO₃The efficiency of the electron blocking EBL device is the same as the device without the electron blocking EBL, indicating that the increased power conversion efficiency is caused by reduced leakage current. In addition, devices with SubPc electron blocking EBL have a higher ratio than with MoO due to increased absorption in the green spectral region and subsequent exciton generation from SnPc₃The device of (3) is more efficient.

It is intended that the specification and examples disclosed herein be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Other than in the examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, analytical measurements and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible unless otherwise indicated. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective measurements.

Claims (30)

1. An organic photosensitive optoelectronic device comprising:

two electrodes comprising an anode and a cathode in overlapping relationship;

at least one donor material, and

at least one acceptor material, wherein the acceptor material is selected from the group consisting of,

wherein the donor material and acceptor material form a photosensitive region between the two electrodes;

at least one electron blocking layer or hole blocking layer located between the two electrodes,

wherein the electron blocking layer and the hole blocking layer comprise at least one material selected from an organic semiconductor, an inorganic semiconductor, a polymer, a metal oxide, or a combination thereof.

2. The device of claim 1, wherein the electron blocking layer comprises a material selected from tris (8-hydroxyquinoline) aluminum (III) (Alq3), N '-bis (3-methylphenyl) - (1, 1' -biphenyl) -4 '-diamine (TPD), 4' -bis [ N- (naphthyl) -N-phenylamino (nba) s]Biphenyl (NPD), subphthalocyanine (SubPc), pentacene, squaric acid, copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), aluminum phthalocyanine chloride (ClAlPc), tris (2-phenylpyridine) (Ir (ppy)₃) At least one organic semiconductor material.

3. The device of claim 1, wherein the electron blocking layer comprises at least one metal oxide of Cu, Al, Sn, Ni, W, Ti, Mg, In, Mo, Zn, and combinations thereof.

4. The device of claim 1, wherein the electron blocking layer comprises at least one of Si, a II-VI semiconductor, and a III-V semiconductor material.

5. The device of claim 1, wherein the hole blocking layer comprises at least one organic semiconductor material selected from naphthalene tetracarboxylic dianhydride (NTCDA), p-bis (triphenylsilyl) benzene (UGH2), 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA), and 7, 7, 8, 8-Tetracyanoterephthalquinodimethane (TCNQ).

6. The device of claim 1, wherein the hole blocking layer comprises a material selected from TiO₂、GaN、ZnS、ZnO、ZnSe、SrTiO₃、KaTiO₃、BaTiO₃、MnTiO₃、PbO、WO₃And SnO₂At least one inorganic material.

7. The device of claim 1, wherein the electron block is in contact with the donor region.

8. The device of claim 1, wherein the hole blocking layer is in contact with the acceptor region.

9. The device of claim 1, wherein the device comprises an electron blocking layer and a hole blocking layer.

10. The device of claim 1, wherein the donor region comprises at least one material selected from CuPc, SnPc, and squaraine.

11. The device of claim 1 wherein the acceptor region comprises a material selected from C₆₀And PTCBI.

12. The device of claim 1, wherein the first photoconductive organic semiconductor material and the second photoconductive organic semiconductor material are selected to be spectrally sensitive in the visible spectrum.

13. The device of claim 1, wherein the first photoconductive organic semiconductor material and the second photoconductive organic semiconductor material are at least partially mixed.

14. The device of claim 1, wherein the photosensitive region forms at least one of a mixed heterojunction, a planar heterojunction, a bulk heterojunction, a nanocrystal-bulk heterojunction, and a mixed planar mixed heterojunction.

15. The device of claim 1, wherein the electron blocking comprises SubPc, CuPc, or MoO₃And has a thickness in the range of aboutTo about

16. The device of claim 1, wherein the hole blocking layer has a thickness in the range ofTo

17. The device of claim 1, wherein the donor region comprises at least one material selected from CuPc and SnPc, the acceptor region comprises C₆₀And the electron blocking layer comprises MoO₃。

18. The device of claim 1, wherein the device is an organic photodetector.

19. The device of claim 1, wherein the device is an organic solar cell.

20. A stacked organic photosensitive optoelectronic device comprising a plurality of photosensitive optoelectronic subcells, wherein at least one subcell comprises:

two electrodes comprising an anode and a cathode in overlapping relationship;

at least one donor material, and

at least one acceptor material, wherein the acceptor material is selected from the group consisting of,

wherein the donor material and acceptor material form a photosensitive region between the two electrodes;

at least one electron blocking layer or hole blocking layer located between the two electrodes,

wherein the electron blocking layer and the hole blocking layer comprise at least one material selected from an organic semiconductor, an inorganic semiconductor, a polymer, a metal oxide, or a combination thereof.

21. The stacked organic photosensitive optoelectronic device of claim 20, wherein the electron blocking layer comprises a material selected from tris (8-hydroxyquinoline) aluminum (III) (Alq3), N '-bis (3-methylphenyl) - (1, 1' -biphenyl) -4 '-diamine (TPD), 4' -bis [ N- (naphthyl) -N-phenylamino ] s]Biphenyl (NPD), subphthalocyanine (SubPc), pentacene, squaric acid, copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), aluminum phthalocyanine chloride (ClAlPc), tris (2-phenylpyridine) (Ir (ppy)₃) At least one organic semiconductor material.

22. The stacked organic photosensitive optoelectronic device of claim 20, wherein the electron blocking layer comprises at least one metal oxide of Cu, Al, Sn, Ni, W, Ti, Mg, In, Mo, Zn, and combinations thereof.

23. The stacked organic photosensitive optoelectronic device of claim 20, wherein the electron blocking layer comprises at least one of Si, II-VI semiconductor materials, and III-V semiconductor materials.

24. The stacked organic photosensitive optoelectronic device of claim 20, wherein the hole blocking layer comprises at least one organic semiconductor material selected from naphthalene tetracarboxylic dianhydride (NTCDA), p-bis (triphenylsilyl) benzene (UGH2), 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA), and 7, 7, 8, 8-Tetracyanoterephthalquinodimethane (TCNQ).

25. The stacked organic photosensitive optoelectronic device of claim 20, wherein the hole blocking layer comprises a material selected from TiO₂、GaN、ZnS、ZnO、ZnSe、SrTiO₃、KaTiO₃、BaTiO₃、MnTiO₃、PbO、WO₃And SnO₂At least one inorganic material.

26. A method of increasing the power conversion efficiency of a photosensitive optoelectronic device by reducing dark current, the method comprising in the device:

at least one electron blocking layer or hole blocking layer,

wherein the electron blocking layer or the hole blocking layer includes at least one material selected from an organic semiconductor, an inorganic semiconductor, a polymer, a metal oxide, or a combination thereof.

27. The method of claim 26, wherein the electron blocking layer comprises a material selected from tris (8-hydroxyquinoline) aluminum (III) (Alq3), N '-bis (3-methylphenyl) - (1, 1' -biphenyl) -4 '-diamine (TPD), 4' -bis [ N- (naphthyl) -N-phenylamino (nba) s]Biphenyl (NPD), subphthalocyanine (SubPc), pentacene, squaric acid, copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), aluminum phthalocyanine chloride (ClAlPc), tris (2-phenylpyridine) (Ir (ppy)₃) At least one organic semiconductor material.

27. The method of claim 26, wherein the electron blocking layer comprises at least one metal oxide of Cu, Al, Sn, Ni, W, Ti, Mg, In, Mo, Zn, and combinations thereof.

28. The method of claim 26, wherein the electron blocking layer comprises at least one of Si, a II-VI semiconductor material, and a III-V semiconductor material.

29. The method of claim 26, wherein the hole blocking layer comprises at least one organic semiconductor material selected from naphthalene tetracarboxylic dianhydride (NTCDA), p-bis (triphenylsilyl) benzene (UGH2), 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA), and 7, 7, 8, 8-Tetracyanoterephthalquinodimethane (TCNQ).

30. The method of claim 26, wherein the hole blocking layer comprises a material selected from TiO₂、GaN、ZnS、ZnO、ZnSe、SrTiO₃、KaTiO₃、BaTiO₃、MnTiO₃、PbO、WO₃And SnO₂At least one inorganic material.