JP6673897B2 - Stable organic photosensitive devices including exciton blocking charge carrier filters using high glass transition temperature materials - Google Patents

Description

(Cross-reference of related applications)
This application claims the benefit of priority of International Application No. PCT / US2014 / 062351 filed October 27, 2014, which is hereby incorporated by reference in its entirety, and further filed on July 18, 2014. Claims the priority benefit of filed US Provisional Application No. 62 / 026,301, which is hereby incorporated by reference in its entirety.

(Statement on Federal Research)
This invention is awarded in the United States under Contract Nos. DE-SC0000957, DE-SC00001313 and DE-EE0005310 awarded by the U.S. Department of Energy, and under FA9550-10-1-0339 awarded by the Air Force Science Research Agency. Made with government support. In the present invention, the government has certain rights.

(Joint research contract)
The subject matter of this disclosure is representative of, and / or in connection with, the University of Michigan, the University of Southern California, and the NanoFlex Power Corporation, one or more organizations for the Joint University Institutional Research Agreement. It was done. This Agreement was effective prior to the date on which the subject matter of this disclosure was prepared, and was made as a result of activities performed within the scope of this Agreement.

  The present invention relates generally to devices that are electronically active, optically active, utilize sunlight, and are semiconductors, and in particular, wide energy gap materials that are morphologically stable at the operating temperature of the device. And an organic photosensitive optoelectronic device comprising at least one exciton blocking charge carrier filter comprising: The present application also discloses a method for preparing the device.

  Opto-electronic devices rely on the optical and electronic properties of materials to generate or detect electromagnetic radiation electronically or to generate power from ambient electromagnetic radiation.

  Photosensitive optoelectronic devices convert electromagnetic radiation into electrical power. Solar cells, also called photovoltaic (PV) devices, are a type of photosensitive optoelectronic device that is used, inter alia, to generate electrical power. PV devices may generate electrical energy from light sources other than sunlight and are used to drive loads that consume power, for example, to provide lighting and heating equipment, or to provide a calculator, radio, computer or Power an electronic circuit or device, such as a remote monitor or communication device. Also, these power generation applications often involve charging batteries or other energy storage devices to allow operation to continue even when direct illumination from the sun or other light sources is not available, or Try to balance the power output of the PV device with specific application requirements. As used herein, the term “resistive load” means a circuit, device, apparatus or system that consumes or stores any power.

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

  Another type of photosensitive optoelectronic device is a photodetector. In operation, a photodetector measures the current generated upon exposure to electromagnetic radiation and is used in conjunction with a current detection circuit that may have an applied bias voltage. A detection circuit as described herein can provide a bias voltage to the photodetector and measure the electrical response of the photodetector to electromagnetic radiation.

  These three categories of photosensitive optoelectronic devices depend on whether a rectifying junction is present, as defined below, and whether the device operates with an external applied voltage, also known as a bias or bias voltage. It may be characterized by whether or not. Photoconductive cells do not have rectifying junctions and typically operate with a bias. PV devices have at least one rectifying junction and operate without bias. Photodetectors have at least one rectifying junction and usually, but not always, operate with a bias. In principle, a photovoltaic cell supplies power to a circuit, device or apparatus, but does not supply a signal or current to control the detection circuit or the output of information from the detection circuit. Conversely, a photodetector or photoconductor provides a signal or current, but does not supply power to a circuit, device or apparatus, to control the detection circuit or the output of information from the detection circuit.

  Traditionally, photosensitive optoelectronic devices have been composed of, for example, crystalline silicon, polycrystalline silicon and amorphous silicon, gallium arsenide, cadmium telluride, and many other inorganic semiconductors. As used herein, the term “semiconductor” refers to a material that can conduct when charge carriers are induced by thermal or electromagnetic excitation. The term "photoconductive" generally relates to the process by which electromagnetic radiant energy is absorbed and thereby converted into the excitation energy of charge carriers, which can conduct (ie, transport) charges in a material. The terms "photoconductor" and "photoconductive material" are used herein to mean a semiconductor material that is selected for its properties of absorbing electromagnetic radiation and generating charge carriers.

  PV devices may be characterized by the efficiency with which incident solar power can be converted to useful power. Devices using crystalline or amorphous silicon are at the heart of commercial applications, with some reaching efficiencies of 23% or more. However, efficient crystal-based devices, especially those with large surface areas, are difficult and expensive to manufacture due to the unique problems of manufacturing large crystals without significant efficiency degradation. On the other hand, high efficiency amorphous silicon devices still have stability problems. In recent years, efforts have been concentrated on the use of organic photovoltaic cells to reach acceptable photovoltaic conversion efficiencies at low manufacturing costs.

Under standard illumination conditions (ie, 1000 W / m ² , standard test conditions that are AM1.5 spectrum illumination), the PV device generates maximum power, ie, the product of photocurrent and photovoltaic. May be optimized so that is maximized. Under standard illumination conditions, the power conversion efficiency of such a cell is determined by three parameters: (1) current under zero bias (ie, short-circuit current I _SC , in amps), and (2). It depends on the photovoltaic under open circuit conditions (ie, open circuit voltage V _OC , in volts), and (3) fill factor FF.

PV devices generate a photogenerated current when connected via a load and illuminated by light. When illuminated under an infinite load, the PV device generates its maximum possible voltage (V open-circuit or V _OC ). When illuminated with its electrical connection shorted, the PV device generates its maximum possible current (I short-circuit or I _SC ). In fact, when used to generate power, the PV device is connected to a finite resistive load and the power output is given by the product of current and voltage (I × V). The maximum total power generated by a PV device cannot inherently exceed the product of I _SC × V _OC . If the value of the load is optimized for maximum power, the current and voltage have the values I _max and V _max respectively.

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

_{Here, I SC} and _{V OC,} since never obtained simultaneously in actual use, FF is always less than 1. Nevertheless, as FF approaches 1, the device will have a lower series or internal resistance, so that under optimal conditions, for a load, the product of I _SC and V _OC Give a greater proportion of. If P _inc is the input of power to the device, the power efficiency η _{P of the} device can be calculated by:

  The usual method for generating an internally generated electric field, which occupies a considerable volume of a semiconductor, is to juxtapose two layers of material, with a conductivity appropriately chosen, especially with respect to the distribution of the quantum energy state of the molecule. That is. The interface between these two materials is called a photovoltaic junction. In conventional semiconductor theory, the materials for forming a PV junction have generally been described as being either n-type or p-type. Here, n-type indicates that the type of majority carrier is an electron. This can be viewed as a material with a large number of electrons in a relatively free energy state. The p-type indicates that the majority carrier type is a hole. Such materials have a large number of holes in relatively free energy states. In the background type (ie, the non-light-generating background type), the majority carrier concentration depends primarily on unintentional doping by defects or impurities. The type and concentration of the impurity determines the value of the Fermi energy (or Fermi level) within the gap between the lowest energy of the conduction band and the highest energy of the valence band, also known as the HOMO-LUMO gap. decide. Fermi energy characterizes the statistical occupation of the quantum energy state of a molecule, indicated by a value of the energy whose occupancy probability is equal to 1/2. Fermi energy near the lowest (LUMO) energy of the conduction band indicates that electrons are the dominant carrier. Fermi energy near the highest (HOMO) energy of the valence band indicates that holes are the dominant carrier. Therefore, Fermi energy is the most characteristic characteristic of a conventional semiconductor, and a prototype PV junction has conventionally been a pn junction surface.

  The term “rectifying” particularly indicates that the interface has asymmetric conduction properties (ie, the interface is preferably responsible for transporting charge in one direction). Rectification is usually associated with a built-in electric field that occurs at the junction between appropriately selected materials.

  An important property in 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 organic photosensitive devices, a layer containing a material that conducts preferentially by electrons due to high electron mobility can be referred to as an electron transport layer or ETL. A layer containing a material that conducts preferentially by holes due to high hole mobility can be referred to as a hole transport layer or HTL. In some cases, the acceptor material may be ETL and the donor material may be HTL.

  Conventional inorganic semiconductor PV cells can use a pn junction to establish an internal electric field. However, it is now recognized that, in addition to the placement of a pn junction, the energy level offset of the heterojunction also plays an important role.

Energy level offsets in organic donor-acceptor (DA) heterojunctions are believed to be important to the operation of organic PV devices due to the fundamental nature of the process of photogeneration in organic materials. Upon photoexcitation of an organic material, localized Frenkel or charge transfer excitons are generated. To effect electrical detection or current generation, the bound exciton must be dissociated into its constituent electrons and holes. Such processes include, but may be induced by the built-in field, efficiency of electric fields typically found (F~10 6 V / ^cm) in an organic device is low. The most efficient exciton dissociation in organic materials occurs at the DA interface. At such a junction surface, a donor material having a low ionization potential forms a heterojunction with an acceptor material having a high electron affinity. Exciton dissociation is likely to occur energetically at such junctions by adjusting the energy levels of the donor and acceptor materials, resulting in free electron polarons in the acceptor material and free hole polarons in the donor material .

  Carrier generation requires exciton generation, diffusion and ionization or collection. There is an efficiency η associated with each of these processes. Subscripts such as P for power efficiency, EXT for external quantum efficiency, A for photon absorption, ED for diffusion, CC for collection, and INT for internal quantum efficiency. Can be used. Using this notation, it is as follows.

Diffusion length of an exciton _{(L D)} is generally the optical absorption length considerably shorter than _{(~500Å) (L D ~50Å)} , comprising a bonding surface which is folded back multiple or highly, thicker resistive hence It requires a trade-off between using a high cell or a thin cell with low light absorption efficiency.

  Organic PV cells have many potential advantages when compared to conventional silicon-based devices. Organic PV cells are lightweight, economical in material use, and can be laminated on low cost substrates such as flexible plastic foils. However, for commercialization, device efficiency must be further improved by new materials and device design methods.

  In organic PV cells, interfacial phenomena can be observed to control behavior in key processes such as charge separation at the donor / acceptor interface and charge extraction at the organic layer / electrode interface. Buffer layers are often used between the photoactive region and one or both electrodes to improve charge extraction while preventing exciton recombination.

  As a buffer, a material having a wide energy gap such as BCP and BPhen (hereinafter, a wide energy gap material) has been used. These materials work by transporting electrons through the defect states induced by the stacking of the cathodes, while blocking exciton transport due to their wide HOMO-LUMO energy gap. The second effect of these wide gap buffers is to place the optical absorbing layer at the optimal location in the light field, away from the reflective cathode. However, these buffers are limited to extremely thin films (<10 nm) due to the depth of penetration of defect states that occur during stacking and have high resistance.

  Materials with low HOMO energy, such as Ru (acac), have been used as buffers to transport holes from the cathode and recombine with electrons at the acceptor / buffer interface.

  A third type of buffer has been developed based on materials that have a LUMO energy tuned to the energy of the acceptor, such as PTCBI and NTCDA. Tuning the LUMO level allows for efficient conduction of electrons from the acceptor to the cathode. Also, these materials can act to block excitons if the HOMO / LUMO gap is large enough. However, these materials can hinder device performance if they absorb in the same spectral region as the active layer material. Improvements to the structure of these devices must be made to increase the conversion efficiency of organic PV cells.

  The inventors of the present invention have developed a new class of buffers disclosed herein as exciton blocking charge carrier filters. These new buffers include a mixture of at least one wide energy gap material and at least one electron or hole conducting material. The filters are optimized by their position on the device. That is, the exciton blocking hole conduction filter is disposed between the photoactive region and the anode to block excitons and conduct holes to the anode. Conversely, exciton blocking electron conducting filters are positioned between the photoactive region and the cathode to block excitons and conduct electrons to the cathode. For example, in an exciton blocking electron filter, electrons are transported by an electron conducting material through an impurity band-like mechanism. At the same time, excitons are blocked by a combination of energy barriers due to the wide energy gap material and statistical barriers due to the reduced number of states used to transfer to the electronic conductor.

The problem with many buffers, such as BCP or BPhen, is that they have high resistance and rely on damage-induced transport states that limit the actual layer thickness to 〜１０10 nm. By mixing a wide energy gap material (eg, BCP) with a material having excellent transport properties (eg, C ₆₀ ), the overall conductivity can be improved by using impurity band-like transport.

A second problem with buffers such as BCP or BPhen is that they operate at temperatures that begin to approach their respective glass transition temperatures (T _g ) and, in some cases, exceed their respective glass transition temperatures (T _g ). At operating temperatures, it can be morphologically unstable, which can cause performance degradation over time and can significantly reduce the operating life of the device. Under such conditions, the buffer can crystallize and degrade. By mixing a wide energy gap material with an electron or hole conductor (such as fullerenes), the inventors of the present invention allow the buffer layer to be buffered, such as in the form of “doped pinning”. It has been found that the stability of the layer is improved. Furthermore, in the exciton blocking charge carrier filters described herein, by using a morphologically stable wide energy gap material, i.e., a wide energy gap material having a sufficiently high glass transition temperature, the operating life of the device is increased. It can be significantly extended.

  Also, the exciton blocking charge carrier filter described herein prevents charge accumulation in the active layer, which helps reduce the exciton-exciton-polaron quenching, and reduces the short circuit current and fill factor of the device. Acts to increase.

In a first aspect of the present disclosure, an organic photosensitive optoelectronic device includes two electrodes in an overlapping relationship, including an anode and a cathode, and at least one disposed between the two electrodes to form a donor-acceptor heterojunction. A photoactive region comprising one donor material and at least one acceptor material, wherein the at least one acceptor material has a lowest unoccupied orbital energy level (LUMO _Acc ) and a highest occupied orbital energy level (HOMO _Acc ). Wherein the at least one donor material has a lowest unoccupied orbital energy level (LUMO _Don ) and a highest occupied orbital energy level (HOMO _Don ) and between the cathode and the at least one acceptor material. Exciton blocking electron filter (here, the electron filter Data includes to include) a mixture containing a wide energy gap material and at least one electron-conducting material of at least one cathode, a wide energy gap material of the at least one cathode side,
A lowest unoccupied orbital energy level (LUMO _CS-WG ) that is equal to or less than the LUMO _Acc ;
A highest occupied orbital energy level (HOMO _CS-WG ) which is _{equal to} or higher than the HOMO _Acc or smaller than 0.3 eV than the HOMO _Acc ;
A HOMO _{CS-WG -} an energy gap of LUMO _CS-WG wider than an energy gap of LUMO _Acc- LUMO _Acc ;
The at least one cathode side wide energy gap material has a glass transition temperature of 85 ° C. or higher.

In a second aspect, an organic photosensitive optoelectronic device comprises two electrodes in an overlapping relationship, including an anode and a cathode, and at least one donor disposed between the two electrodes to form a donor-acceptor heterojunction. A photoactive region comprising a material and at least one acceptor material, wherein said at least one donor material has a lowest unoccupied orbital energy level (LUMO _Don ) and a highest occupied orbital energy level (HOMO _Don ). An exciton blocking hole filter disposed between the anode and the at least one donor material, wherein the hole filter comprises at least one anode side wide energy gap material and at least one hole conduction A mixture comprising a material). The wide energy gap material on the side
The highest occupied orbital energy level (HOMO _AS-WG ) which is equal to or higher than the HOMO _Don ;
The lowest unoccupied orbital energy level (LUMO _AS-WG ) that is equal to or less than the LUMO _Don or greater than 0.3 LU (farther from vacuum) than the LUMO _Don ;
A HOMO _{AS-WG -} an energy gap of LUMO _AS-WG wider than the energy gap of LUMO _Don- LUMO _Don ;
The at least one anode side wide energy gap material has a glass transition temperature of 85 ° C. or higher.

The accompanying drawings are incorporated into and constitute a part of this specification.
1 is a schematic diagram illustrating an example of an organic photosensitive optoelectronic device according to the present disclosure. Device A includes an exciton blocking electron filter or an exciton blocking hole filter. Device B includes an exciton blocking electron filter and an exciton blocking hole filter. 1: 0 (left triangle), 3: 1 (down triangle), 1: 1 (circle), 1: 2 (square), and 0: 1 (calculated from k determined by variable angle spectroscopic ellipsometry). FIG. 4 is a diagram showing an absorption spectrum of a C ₆₀ : BCP film having a volume doping ratio of (rightward triangle). The inset shows the absorbance of the attenuation as a function of the ratio of C _60. It is 450 nm (square) and 360 nm (circle). The upper figure shows the JV curve of the device under 1 sun, AM1.5G irradiation, including insets showing the characteristics of the device. The figure below shows a plot of the external quantum efficiency, including an inset showing the structure of the device. (A: B) = 1: 0 (D1), 2: 1 (D2), 1: 1 (D3), 1: 2 (D4). The upper figure shows the JV curve of the device under 1 sun, AM1.5G irradiation. The figure below shows a plot of the external quantum efficiency, including an inset showing the structure of the device. x = 10 nm (D7), 20 nm (D6), and 30 nm (D5). The upper figure shows the JV curve of the device under 1 sun, AM1.5G irradiation. The figure below shows a plot of the external quantum efficiency, including an inset showing the structure of the device. x = 0 nm (D8), 20 nm (D9), and 40 nm (D10). The upper figure shows the JV curve of the device under 1 sun, AM1.5G irradiation. The figure below shows the external quantum efficiency and includes an inset showing the structure of the device. "The _{1C 60} thickness" donor comprises DPSQ (x = 5nm, 15nm, 25nm, 35nm) and - means a thickness of at least one acceptor material forming the acceptor heterojunction. The upper figure shows the JV curve of the device under 1 sun, AM1.5G irradiation. The figure below shows the external quantum efficiency and includes an inset showing the structure of the device. Figure 4 shows the external quantum efficiency under applied bias (+ 0.5V for dashed line, -1V for solid line), normalized to EQE at zero bias, for various buffer layers. In the mixed film used for the movement of excitons, based only on the number of molecules of reduced C _60, on the net C ₆₀ active layer BCP: for exciton diffusion for mixed layer of C _60, Monte Carlo simulation FIG. Excitons are generated randomly in the active layer. They move randomly during a predetermined number of steps and their final position is recorded. They are assumed to be spread only by nearest hopping. In the interface between the mixed layer and the active layer, probability for hopping between the layers is measured by the relative number of molecules of C ₆₀ in each layer. The figure is a diagram showing an absorption spectrum normalized C ₇₀ covered with different buffer layers. Below is a diagram showing an emission spectrum of the quenching layer (NPD), blocking layer (BCP) and mixtures covered with a buffer layer (excited at 450 _{nm) C 70.} The upper figure shows the EQE spectra of devices covered with various buffer layers. The lower figure shows the JV curve of the device under 0.8 sun, AM1.5G irradiation. The upper figure shows the JV curve of the device under 1 sun, AM1.5G irradiation. The figure below shows a plot of the external quantum efficiency, including an inset showing the structure of the device. Buffer, 10 nm of BCP (D11), 10nm of _{C 60: BCP (D12),} 10nm of PTCBI (D13), 10nm of _C 60: BCP / 5nm of PTCBI (D14), 10nm of _BCP: C 60 / 5nm of BCP (D15). The top diagram shows the EQE at -1V, normalized to the EQE at 0V, for the device of FIG. 12 including various buffer layers. The figure below shows the response as a function of the illumination intensity for the device. Buffer, 10 nm of BCP (D11), 10nm of _{BCP: C 60 (D12),} 10nm of PTCBI (D13), 10nm of _BCP: C 60 / 5nm of PTCBI (D14), 10nm of _BCP: C 60 / 5nm of BCP (D15). The upper figure shows the JV curve of the device under 1 sun, AM1.5G irradiation. The figure below shows a plot of the external quantum efficiency, including an inset showing the structure of the device. x = 5 nm (D16), 15 nm (D17), 25 nm (D18), and 35 nm (D19). The upper figure shows the JV curve of the device including various buffer layers under 1 sun, AM1.5G irradiation. The figure below shows a plot of the external quantum efficiency of a device including various buffer layers. The figure _illustrates a device including various buffer layers containing different ratios of _{C 60} pairs BCP, 1 sun, the J-V curves under AM1.5G illumination. The figure below shows a device including various buffer layers containing different ratios of C ₆₀ pairs BCP, is a plot of external quantum efficiency. Relatively thick, of a pure layer of DBP and _{C 70} 1: about 8 plan mixed OPV cell including an active layer having a volume ratio of, 1 sun, in the pseudo AM1.5G irradiation, J-V relates irradiation (upper left), EQE (Top right) and extracted efficiency parameters (bottom). Each buffer regarding thickness and _BPhen: the volume ratio of _{C 70,} shown in Table. J for irradiation in 0.7 sun, quasi AM1.5G irradiation for a planar mixed OPV cell containing a relatively thin, active layer having a 1: 8 volume ratio of DBP to a pure layer of C ₇₀ and various buffers. FIG. 7 shows -V (upper left), EQE (upper right), and extracted efficiency parameters (lower). Each thickness about the buffer and _BCP: the volume ratio of _{C 70,} shown in Table. FIG. 4 shows EQE and JV curves for a dilution comprising BPhen, CBP and UGH2. (A) it is, _DBP: on Mixing HJ OPV cells _{C 70,} pseudo AM1.5G, under irradiation of 1 sun, is a diagram showing characteristics of a spectrum corrected current density vs. voltage (J-V). The shaded area highlights the difference between the fill factors of the two cells (ie, the output with the highest power). The inset shows a schematic view of the structure of the device. (B) is a diagram showing an external quantum efficiency (EQE) spectrum for the cell in (a). Inset, _DBP: shows a schematic diagram of the energy levels in the _{C 70} / buffer junction surface (Left: Jun BPhen buffer, right: _BPhen: buffer of the compounds of _{C 60).} FIG. 4 shows the response to light intensity for mixed HJ control cells and compound buffer cells using a linear fit (broken line) according to the theory of bimolecular recombination. (A) is a figure which shows the electric charge extraction time with respect to an electric field regarding the thickness of various layers calculated using 3D Monte Carlo simulation. The inset shows the cell's series resistance (R _s ) versus layer thickness using a linear fit (dashed line) to the data obtained from the OPV cells (squares). Smaller). (B) is, lambda = 520 nm excitation BPhen (blocking layer) obtained at a wavelength, NPD (quenching layer) and _BPhen: about _{C 60} in contact with the mixed layer of pure _{C 70} layer, shows a photoluminescence (PL) spectrum It is. (A) Spectral corrected current density (JV) versus voltage under simulated AM1.5G, 1 sun irradiation for a DBP: C ₇₀ PM-HJ OPV cell with various buffer layers. FIG. 6 is a diagram showing characteristics of the present invention. (B) is, DBP include various buffer _layer: about PM-HJ OPV cells _{C 70,} is a diagram illustrating an external quantum efficiency spectrum. FIG. 9 is a diagram showing calculated absorption spectra and internal quantum efficiencies of a control cell and a cell including a BPhen: C ₆₀ / BPhen buffer. And control cell, _BPhen: and to a cell containing a C 60 / BPhen buffer is a diagram showing the response to the light intensity (black squares) and power conversion efficiency (open squares). (A) is, _BPhen: in C 60 / BPhen cell containing a buffer, _BPhen: as a function of the thickness of the _{C 60} mixed layer, pseudo AM1.5G, under irradiation of 1 sun, the spectrum corrected J-V It is a figure showing a characteristic. (B) it is, _BPhen: in C 60 / BPhen cell containing a buffer, _BPhen: as a function of the thickness of the _{C 60} mixed layer is a diagram illustrating an external quantum efficiency spectrum. FIG. 3 shows the modeled average extraction time versus electric field as a function of BPhen: C ₆₀ mixed layer thickness. The inset shows the series resistance with mixed layer thickness with the fit. (A) comprises an active layer composed of DBP and _{C 60,} about the OPV cell containing a variety of buffers, illustrates 1 sun, under pseudo AM1.5G irradiation, the J-V about radiation. Inset shows NPD. (B) relates OPV cell comprising an active layer made of DBP and _{C 60,} and various buffers, a diagram illustrating an external quantum efficiency. 1 is a schematic diagram illustrating an example of a series organic photosensitive optoelectronic device according to the present disclosure. Device A includes an exciton blocking electron filter or an exciton blocking hole filter. Device B includes an exciton blocking electron filter and an exciton blocking hole filter. Mixture comprising a thin BPhen cap layer between the mixed buffer layer and the Al electrode (5nm) _{BPhen: C 60} buffer layer comprises a (10 nm), or a thin TPBi cap layer between the mixed buffer layer and the Al electrode (3 nm) FIG. 3 shows a DBP: C ₇₀ device including a mixed TPBi: C ₇₀ buffer layer (10 nm). Mixed with thin BPhen capping layer _{BPhen: C 60} for the device of Figure 30 including a buffer layer, the normalized response at 50 ° C. over time is a diagram illustrating the fill _{factor, V OC} and PCE. FIG. 31 shows normalized response, fill factor, _VOC and PCE at 60 ° C. over time for the device of FIG. 30 including a mixed BPhen: C ₆₀ buffer layer with a thin BPhen cap layer. Mixed with thin BPhen capping layer _{BPhen: C 60} for the device of Figure 30 including a buffer layer, the normalized response at 80 ° C. over time is a diagram illustrating the fill _{factor, V OC} and PCE. Mixed with thin TPBi capping layer _{TPBi: C 60} for the device of Figure 30 including a buffer layer, the normalized response at 50 ° C. over time is a diagram illustrating the fill _{factor, V OC} and PCE. Mixed with thin TPBi capping layer _{TPBi: C 60} for the device of Figure 30 including a buffer layer, the normalized response at 80 ° C. over time is a diagram illustrating the fill _{factor, V OC} and PCE. Mixed with thin TPBi capping layer _{TPBi: C 60} for the device of Figure 30 including a buffer layer, the normalized response at 105 ° C. over time is a diagram illustrating the fill _{factor, V OC} and PCE. Mixed with thin TPBi capping layer _{TPBi: C 60} for the device of Figure 30 including a buffer layer, the normalized response at 130 ° C. over time is a diagram illustrating the fill _{factor, V OC} and PCE. FIG. 4 shows normalized power conversion efficiency over time of a DBP: C ₇₀ mixed heterojunction including various buffers. It is a figure which shows the molecular structure of BAlq which is an example of a wide energy gap material. It is a figure showing the molecular structure of TPBi which is an example of a wide energy gap material. Is a diagram showing the molecular structure of Alq ₃ is an example of a wide energy gap material. It is a figure which shows the molecular structure of BP4mPy which is an example of a wide energy gap material. It is a figure which shows the molecular structure of 3TPYMB which is an example of a wide energy gap material. Relates to a device comprising a mixing buffer comprising a mixture of C ₇₀ and TPBi, normalized response at 55 ° C. over time is a diagram illustrating the fill factor, V _OC and PCE. Relates to a device comprising a mixing buffer comprising a mixture of C ₇₀ and 3TPYMB, normalized response at 55 ° C. over time is a diagram illustrating the fill _{factor, V OC} and PCE. FIG. 4 shows normalized response, fill factor, _VOC and PCE at 55 ° C. over time for a device containing a mixing buffer containing a mixture of C ₇₀ and BAlq. FIG. 3 illustrates a DBP: C ₇₀ device including a mixed 3TPYMB: C ₆₀ buffer layer. FIG. 43 shows normalized response, fill factor, _VOC and PCE over time at 55 ° C. for the device of FIG. 42. FIG. 43 shows normalized response, fill factor, _VOC and PCE over time at 70 ° C. for the device of FIG. 42. FIG. 43 shows normalized response, fill factor, _VOC and PCE over time at 85 ° C. for the device of FIG. 42. FIG. 43 shows normalized response, fill factor, _VOC and PCE over time for the device of FIG. 42 at 100 ° C.

  As used herein, the term "organic" includes polymeric and small molecule organic materials that may be used to make organic photosensitive devices. "Small molecule" means any organic material that is not a polymer, and "small molecule" may actually be quite large. Small molecules may optionally include repeating units. For example, using a long chain alkyl group as a substituent does not exclude a molecule from the "small molecule" classification. Also, small molecules may be incorporated into the polymer, for example, as pendant groups on the polymer backbone or as part of the backbone.

  In the organic materials of the present disclosure, the terms “donor” and “acceptor” refer to the relative occupied orbital (HOMO) and lowest unoccupied orbital (LUMO) energy levels of two joined but different organic materials. Means position. If the LUMO energy level of one material in contact with another material is far from the vacuum level, that material is an acceptor. If not, it is a donor. In the absence of an external bias, the transfer of electrons at the donor-acceptor junction to the acceptor material and the transfer of holes to the donor material are energetically likely.

  As used herein, the term “cathode” is used as follows. Under ambient illumination, in a non-stacked PV device or a single unit of a stacked PV device (eg, a solar cell) connected to a resistive load without an external applied voltage, electrons are transferred from adjacent photoconductive material to the cathode. Go to Similarly, the term "anode" is used herein to refer to holes moving from an adjacent photoconductive material to the anode in a solar cell under irradiation, which refers to the reverse movement of electrons. Equivalent to. It should be noted that the "anode" and "cathode" electrodes may be charge transport or recombination regions, such as the electrodes used in photovoltaic devices in series. In photosensitive optoelectronic devices, it is desirable that a maximum amount of ambient electromagnetic radiation from outside the device be accommodated in the photoconductively active interior region. That is, the electromagnetic radiation must reach the photoconductive layer, where it can be converted to electricity by photoconductive absorption. This often dictates that at least one of the electrical contacts should minimally absorb and minimally reflect incoming electromagnetic radiation. In some cases, such contacts should be transparent or at least translucent. An electrode is said to be "transparent" if it transmits at least 50% of the surrounding electromagnetic radiation at the relevant wavelength. An electrode is said to be "translucent" if it transmits some, but less than 50% of the surrounding electromagnetic radiation at the relevant wavelength. The reflective electrode may be a reflective material such that light that has passed through the cell without being absorbed is reflected back through the cell.

  As used herein, "photoactive region" refers to a region of a device that absorbs electromagnetic radiation to generate excitons. Similarly, a layer is "photoactive" if it absorbs electromagnetic radiation to generate excitons. Excitons can dissociate into electrons and holes to generate a current.

  As used and described herein, a "layer" refers to an element or component of a photosensitive device whose primary dimension is XY (i.e., along its length and width). It should be understood that the term layer is not necessarily limited to a single layer or sheet of material. Further, the surface of one layer, including the interface between such a layer and another material or layer, may be imperfect, and the surface may be infiltrated or mixed with other materials or layers. It is to be understood that a network can be complicated. Similarly, it should also be understood that the layers may be discontinuous, such that continuity of the layers along the XY dimension may be impeded or interfered with by other layers or materials. It is.

  As used herein, a first HOMO or LUMO energy level is "less than" a second HOMO or LUMO energy level if it is closer to a vacuum level than a second HOMO or LUMO energy level. Similarly, a first HOMO or LUMO energy level is "greater than" a second HOMO or LUMO energy level if it is farther from the vacuum level than the second HOMO or LUMO energy level.

  As used herein, the energy levels of two orbitals are "equal" to each other, as their terms are used herein, if their energies match up to ten decimal places. For example, in the present disclosure, a LUMO energy of -3.70 eV is considered "equal to" a LUMO energy of -3.79 eV.

LUMO _Acc and HOMO _Acc , as used herein, represent the lowest unoccupied orbital energy level and the highest occupied orbital energy level, respectively, of at least one acceptor material.

LUMO _Don and HOMO _{Don as} used herein represent the lowest unoccupied orbital energy level and the highest occupied orbital energy level, respectively, of at least one donor material.

LUMO _CS-WG and HOMO _{CS-WG as} used herein represent the lowest unoccupied orbital energy level and the highest occupied orbital energy level, respectively, of at least one cathode-side wide energy gap material.

LUMO _AS-WG and HOMO _{AS-WG as} used herein represent the lowest unoccupied orbital energy level and the highest occupied orbital energy level, respectively, of at least one anode-side wide energy gap material.

LUMO _EC and HOMO _{EC as} used herein represent the lowest unoccupied orbital energy level and the highest occupied orbital energy level, respectively, of at least one electron conducting material.

LUMO _HC and HOMO _{HC as} used herein represent the lowest unoccupied orbital energy level and the highest occupied orbital energy level, respectively, of at least one hole conducting material.

  As used herein, the HOMO-LUMO gap is the energy difference between the HOMO and LUMO of a material.

As used herein, the term “between” in the context of describing a range of glass transition temperature (T _g ) values for a wide energy gap material is meant to include the endpoint value.

  The device of the present disclosure includes at least one exciton blocking charge carrier filter. As an example, a schematic diagram of an organic photosensitive optoelectronic device according to the present disclosure is shown in FIG. The electrode 110 includes an anode or a cathode. Where electrode 110 includes a cathode, electrode 140 includes an anode. When electrode 110 includes an anode, electrode 140 includes a cathode. The photoactive region includes donor / acceptor organic layers 120 and 130 to form a donor-acceptor heterojunction as described herein. The photoactive region may include additional donor and / or acceptor layers, for example, to form a hybrid planar mixed heterojunction. Organic layer 120 includes at least one donor material or at least one acceptor material. When the organic layer 120 includes at least one acceptor material, the organic layer 130 includes at least one donor material. When the organic layer 120 includes at least one donor material, the organic layer 130 includes at least one acceptor material. It should be noted that the donor / acceptor layers in FIG. 1 need not be planar. That is, the present disclosure contemplates all types of donor-acceptor heterojunctions that are well known in the art for organic photovoltaic devices, and specifically includes those described herein.

  In device A of FIG. 1, if electrode 110 comprises a cathode, organic layer 120 comprises at least one acceptor material, organic layer 130 comprises at least one donor material and electrode 140 comprises an anode, layer 115 comprises This is an exciton blocking electron filter. If electrode 110 includes an anode, organic layer 120 includes at least one donor material, organic layer 130 includes at least one acceptor material, and electrode 140 includes a cathode, layer 115 may be an exciton blocking hole filter. is there.

  In some embodiments, the device, like device B, includes both an exciton blocking electron filter and an exciton blocking hole filter. Electrode 110 includes a cathode, organic layer 120 includes at least one acceptor material, organic layer 130 includes at least one donor material, layer 135 is an exciton blocking hole filter, and electrode 140 includes an anode. , Layer 115 is an exciton blocking electron filter. If electrode 110 includes an anode, organic layer 120 includes at least one donor material, organic layer 130 includes at least one acceptor material, layer 135 is an exciton blocking electron filter, and electrode 140 includes a cathode, Layer 115 is an exciton blocking hole filter.

  Although not shown in FIG. 1, devices A and B may include an additional buffer or cap layer located between the exciton blocking electron / hole filter and the nearest electrode.

The exciton blocking electron filter is disposed between the cathode and the at least one acceptor material and includes a mixture comprising at least one cathode side wide energy gap material and at least one electron conducting material. At least one cathode side wide energy gap material comprises:
The lowest unoccupied orbital energy level (LUMO _CS-WG ) which is equal to or less than LUMO _Acc ;
A highest occupied orbital energy level (HOMO _CS-WG ) which is _{equal to} or greater than HOMO _Acc or smaller than 0.3 eV than HOMO _Acc ;
- it has an energy gap of _HOMO Acc _-LUMO wide _HOMO CS-WG than the energy gap of _{Acc -LUMO CS-WG,} a.

At least one electron-conducting material _has a at least _{LUMO Acc,} or small in the range of 0.3eV than _{LUMO Acc} (e.g., small in the range of 0.2 eV) lowest unoccupied molecular orbital energy level (LUMO _EC) .

  In order to extend the operating life of the device by using morphologically stable materials, some embodiments of the present invention may require, for example, higher than the maximum operating temperature of the device, higher than the temperature or temperature range at which the device generally operates. A wide energy gap material on the cathode side is used that has a sufficiently high glass transition temperature, such as high, above a threshold temperature.

In some embodiments, the HOMO _CS-WG is greater than the HOMO _Acc , for example, at least 0.2 eV greater, at least 0.3 eV greater, at least 0.5 eV greater, at least 1 eV greater, at least 1.5 eV greater, or at least 1.5 eV greater. The LUMO _CS-WG is 2 eV larger and the LUMO _CS-WG is smaller than the LUMO _Acc , for example, at least 0.2 eV smaller, at least 0.3 eV smaller, at least 0.5 eV smaller, at least 1 eV smaller, at least 1.5 eV smaller, or at least 2 eV smaller.

In some embodiments, LUMO _EC is equal to LUMO _Acc .

In some embodiments, LUMO _EC is greater than LUMO _Acc , for example, greater than 0.5 eV, greater than 0.4 eV, greater than 0.3 eV, or greater than 0.2 eV. Large within range.

In some embodiments, LUMO _EC is 0.1 eV less than or greater than LUMO _Acc .

In some embodiments, the LUMO _CS-WG is less than the LUMO _EC , eg, at least 0.2 eV less, at least 0.3 eV less, at least 0.5 eV less, at least 1 eV less, at least 1.5 eV less, or at least 1.5 eV less. 2 eV smaller.

In some embodiments, the LUMO _CS-WG is less than 0.2 eV less than LUMO _Acc , for example, less than 0.3 eV, less than 0.5 eV, less than 1 eV, and 1. It is smaller than 5 eV or smaller than 2 eV.

  In some embodiments, the at least one cathode side wide energy gap material is bathocuproine (BCP), bathophenanthroline (BPhen), p-bis (triphenylsilyl) benzene (UGH-2), (4,4 ′). -N, N'-dicarbazole) biphenyl (CBP), N, N'-dicarbazolyl-3,5-benzene (mCP), poly (vinylcarbazole) (PVK), phenanthrene, alkyl and / or aryl-substituted phenanthrene, alkyl And / or aryl substituted derivatives of benzene, triphenylene and alkyl and / or aryl substituted triphenylene, aza substituted triphenylene, oxadiazole, triazole, aryl-benzimidazole, adamantane and alkyl and And / or aryl-substituted adamantane, tetraarylmethane and its derivatives, 9,9-dialkyl-fluorene and its oligomers, 9,9-diaryl-fluorene and its oligomers, spiro-biphenyl and its substituted derivatives, corannulene and its alkyl and / or Or aryl-substituted derivatives, as well as materials selected from those derivatives.

For example, higher than the temperature or temperature range the device operates in general, higher than the highest operating temperature of the device, has a sufficiently high T _g of the like above the temperature threshold, by using the cathode side of the wide energy gap materials, devices May be increased in operating life. For example, as seen in FIGS. 31A-31C and FIGS. 32A-32D, a mixture of BPhen: C ₆₀ (BPhen T _g ｇ62 ° C.) with increasing operating temperature from 50 ° C. to 80 ° C. The decrease in performance over time (ie, normalized responsivity, fill factor, _VOC and PCE) of the exciton blocking charge carrier filter including TPBi as the operating temperature increases from 50 ° C. to 130 ° C. : Faster than the degradation over time of an exciton blocking charge carrier filter containing a mixture of C ₇₀ (T _{g of} TPBi ≒ 122 ° C.). That is, the performance of the device using TPBi: C ₇₀ decreases more slowly over time, even at higher operating temperatures than the device using BPhen. Thus, the efficiency and operating life of the device can be improved, for example, by replacing BPhen and blocking materials with similar T _g values with a cathode side wide energy gap material with a higher T _g , such as TPBi.

In some embodiments, the at least one cathode side wide energy gap material is sufficiently high, for example, above the temperature or temperature range at which the device will generally operate, above the maximum operating temperature of the device, above the threshold temperature, etc. It comprises a material having a high _{T g.} For example, in some embodiments, the at least one cathode side wide energy gap material is 3,3 ′, 5,5′-tetra [(m-pyridyl) -phen-3-yl] biphenyl (BP4mPy), 2,2 ′, 2 ″-(1,3,5-benzintriyl) -tris (1-phenyl-1-H-benzimidazole) (TPBi), bis (2-methyl-8-quinolinolate) -4- (Phenylphenolato) aluminum (BAlq), tris (8-hydroxy-quinolinato) aluminum (Alq3), tris (2,4,6-trimethyl-3- (pyridin-3-yl) phenyl) borane (3TPYMB), , 40- (1,3-phenylene) bis (2,6-di-tolylpyridine-3,5-dicarbonitrile) (m-MPyCN), 4,40- ( , 3-Phenylene) bis (2,6-di (biphenyl-4-yl) pyridine-3,5-dicarbonitrile) (m-PhPyCN), 4,40- (1,3-phenylene) bis (2 6-diphenylpyridine-3,5-dicarbonitrile) (m-PyCN), 6,60- (1,4-phenylene) bis (2-phenyl-4-p-tolylnicotinonitrile) (p-PPtNN) 4,40- (1,4-phenylene) bis (2-phenyl-6-p-tolynicotinonitrile) (p-PPtNT), tris (6-fluoro-8-hydroxy-quinolinato) aluminum (6FAlq3), 2,6-bis (4-cyanophenyl) -4-phenylpyridine-3,5-dicarbonitrile (CNPyCN), 4,40- (1,4-phenylene) bis (2,6-di- Rylpyridine-3,5-dicarbonitrile) (p-MPyCN), bisbenzimidazo [2,1-a: 1 ′, 2-b ′] anthra [2,1,9-def: 6,5,10- d'e'f '] diisoquinoline-10,21-dione (PTCBI), 5,10,15-tribenzyl-5H-diindolo [3,2-a: 3', 2'-c] carbazole (TBDI), 5,10,15-triphenyl-5H-diindolo [3,2-a: 3 ′, 2′-c] carbazole (TPDI), 1,3-bis [3,5-di (pyridin-3-yl) Phenyl] benzene (BmPyPhB), 1,3,5-tri (m-pyridin-3-ylphenyl) benzene, 1,3,5-tris (3-pyridyl-3-phenyl) benzene, 3,3 ′-[ 5 '-[3- (3-pyridinyl) phenyl] [1, ': 3', 1 "-terphenyl] -3,3" -diyl] bispyridine (TmPyPB), 9,9-dimethyl-10- (9-phenyl-9H-carbazol-3-yl) -9,10- Material selected from dihydroacridine (PCZAC), 3,3-di (9H-carbazol-9-yl) biphenyl (mCBP), 4,40-bis (triphenylsilyl) -biphenyl (BSB), and derivatives thereof including.

  In some embodiments, the glass transition temperature of the wide energy gap material on the cathode side is 85 ° C or higher, 95 ° C or higher, 105 ° C or higher, 115 ° C or higher, 125 ° C or higher, 135 ° C or higher, 145 ° C or higher, 155 ° C. The temperature is 165 ° C or more, 175 ° C or more, 185 ° C or more, 195 ° C or more, 200 ° C or more, 225 ° C or more, or 250 ° C or more.

  In some embodiments, the glass transition temperature of the wide energy gap material on the cathode side is between 85 and 200C, for example, between 90 and 195C, between 95 and 190C, between 100 and 185C. Between 105-180 ° C, between 110-175 ° C, between 115-170 ° C, or between 120-165 ° C. It should be noted that materials having a glass transition temperature higher than 200C, for example between 200-300C, 200-275C, 200-250C, or 200-225C, may be used.

The operating temperature of the device changes and depends on many factors, for example, ambient conditions (such as temperature and light intensity) and whether an enhancement mechanism (such as a solar concentrator) is used with the device. Can. For example, the ambient temperature may change depending on the geographic location, time, time, etc. of the device. Similarly, light intensity may also depend on geographic location, time of day, time of day, cloud cover, angle of incidence and other factors. Thus, in some embodiments, the wide energy gap material on the cathode side may, for example, provide a device under normal ambient conditions that is higher than the temperature or temperature range at which the device typically operates (eg, at normal ambient conditions). having, such as higher than the highest operating temperature, a sufficiently high T _g.

In some embodiments, a solar concentrator may be integrated with or used with the device to increase, enhance, or enhance the light directed to the device. The use of concentrators and / or other intensifying mechanisms can increase the operating temperature of the device beyond that experienced by the device under normal ambient conditions. Thus, to increase the stability and operating life of the device, the wide energy gap material on the cathode side may have a _Tg higher than the maximum operating temperature experienced by the device under enhanced lighting conditions.

In some embodiments, at least one acceptor material is a dipyrine complex such as a subphthalocyanine, a subnaphthalocyanine, a zinc dipyrine complex, a BODIPY complex, a perylene, a naphthalene, a fullerene and a fullerene derivative (eg, PCBM, ICBA, ICMA, etc.), And materials selected from carbonyl-substituted polythiophenes, cyano-substituted polythiophenes, polyphenylenevinylenes, or polymers containing electron-deficient monomers such as perylenediimide, benzothiadiazole, or polymers such as fullerene polymers. C ₆₀ , C ₇₀ , C ₇₆ , C ₈₂ , C ₈₄ or derivatives thereof, for example, phenyl-C ₆₁ -butyric acid-methyl ester ([60] PCBM), phenyl-C ₇₁ -butyric acid-methyl ester ([70] PCBM) or thienyl-C ₆₁ -butyric acid-methyl ester ([60] ThCBM), and 3,4,9,10-perylenetetracarboxylic acid-bisbenzimidazole (PTCBI), hexadecafluorophthalocyanine (F ₁₆ CuPc), And their derivatives, such as those selected from other acceptors.

In some embodiments, the at least one electronically conductive material is a dipyrine complex such as a subphthalocyanine, a subnaphthalocyanine, a zinc dipyrine complex, a BODIPY complex, a perylene, a naphthalene, a fullerene, and a fullerene derivative (eg, PCBM, ICBA, ICMA, etc.). As well as polymers such as carbonyl-substituted polythiophenes, cyano-substituted polythiophenes, polyphenylenevinylenes, or polymers containing electron-deficient monomers such as perylenediimide, benzothiadiazole, or fullerene polymers. C ₆₀ , C ₇₀ , C ₇₆ , C ₈₂ , C ₈₄ or derivatives thereof such as phenyl-C ₆₁ -butyric acid-methyl ester ([60] PCBM), phenyl-C ₇₁ -butyric acid-methyl ester ([70] PCBM ) Or thienyl-C ₆₁ -butyric acid-methyl ester ([60] ThCBM), and 3,4,9,10-perylenetetracarboxylic acid-bisbenzimidazole (PTCBI), hexadecafluorophthalocyanine (F ₁₆ CuPc), and It is not limited to those selected from other acceptors such as derivatives thereof.

  In some embodiments, the at least one acceptor material comprises a material selected from a fullerene and a functionalized fullerene derivative. In some embodiments, the at least one electron conducting material comprises a material selected from a fullerene and a functionalized fullerene derivative.

Fullerenes are of particular interest for use as at least one electron conducting material. C ₆₀ has, for example, two peaks at wavelengths of 260 nm and 340 nm due to an allowed electronic transition that results in an excited state of Frenkel type (ie, a single molecule) while absorption at long wavelengths is due to a symmetric forbidden transition. Liquid has an absorption spectrum. In the transition from the liquid to the solid state, C ₆₀ can be determined by the generation of an intermolecular charge transfer (CT) state, for example, resulting from the excitation of electrons from the HOMO of one fullerene to its nearest LUMO, λ = It shows a significant increase in absorption between 400 and 550 nm. If the C _60, mixed with the cathode side of the wide energy gap materials, such as BCP, absorption of CT state is reduced more rapidly than the absorption due to the characteristics of the Frenkel type. Therefore, when fullerene is mixed with the cathode side wide energy gap material, it does not generate excitons in the fullerene electronically conductive material that does not contribute to the efficiency of the device (70% C ₆₀ and 30% wide gap material). It can be used as an excellent electron conducting material with reduced absorption (even at moderate dilutions, such as).

In some embodiments, the at least one electronically conductive material comprises a material selected from C ₆₀ and C _70.

In some embodiments, at least one acceptor material and at least one electron conducting material comprise the same material. In certain embodiments, the same material is a fullerene or a functionalized fullerene derivative. In some embodiments, the same material _{is C 60} or _{C 70.} In some embodiments, the at least one acceptor material and the at least one electron conducting material comprise different materials.

  In some embodiments, the at least one acceptor material and the at least one electron conducting material are selected from different fullerenes and functionalized fullerene derivatives.

  In some embodiments, the mixture comprises at least one cathode side wide energy gap material and at least one electron conducting material in a volume ratio of about 10: 1 to 1:10, for example, about 8: 1 by volume. １ ： 1: 8, a volume ratio of about 6: 1 to 1: 6, a volume ratio of about 4: 1 to 1: 4, or a volume ratio of about 2: 1 to 1: 2. In some embodiments, the ratio is about 1: 1. It should be understood that the specified ratios include integer and non-integer values.

  In some embodiments, the donor-acceptor heterojunction is selected from a mixed heterojunction, a bulk heterojunction, a planar heterojunction, and a hybrid planar mixed heterojunction. In some embodiments, the donor-acceptor heterojunction is a hybrid planar mixed heterojunction (PM-HJ). For example, in a PM-HJ structure, there are two major loss mechanisms that can result in low FF. One is the recombination of two molecules of free charge carriers in the extensive donor-acceptor mixing region of the PM-HJ structure, where the velocity is given by kBM = γ · n · p. Here, γ is the Langevin recombination constant, and n (p) is the free electron (hole) density. The second major loss is due to exciton-polaron quenching in the pure acceptor layer. Electron-polaron accumulation is observed at the pure acceptor / blocking layer interface, resulting in quenching and, therefore, a decrease in internal quantum efficiency (IQE). It should be noted that since both exciton and polaron concentrations are proportional to intensity, exciton-polaron quenching follows a similar relationship as bimolecular recombination. Both mechanisms result in photocurrent loss under forward bias, which increases the slope of the current density-voltage (JV) characteristic in the fourth quadrant, and ultimately reduces both FF and PCE. sell.

An exciton blocking electron filter located between the photoactive region and the cathode can increase the efficiency of the double layer OPV cell. Electron conductive materials efficiently conduct electron-polarons, and wide energy gap materials block excitons. Due to the ability of the electronic filter to spatially separate excitons and polarons at the blocking interface, exciton-polaron quenching can be significantly reduced in double layer cells using such electronic filters. Similarly, While _{this V OC} and FF remains _unchanged, it can lead to significant increase of _{J SC.} Further, the PM-HJ cell has a problem of recombination of two molecules in the mixed photoactive layer. However, the filter (mixed layer) of the present disclosure results in a reduced interfacial area, including the active layer, due to the increased conductivity as compared to a conventional blocking buffer layer that is a pure layer. The resulting increase in electric field across the photosensitive region results in more rapid charge extraction. This, in turn, results in reduced recombination of the two molecules in the cell.

In some embodiments, the device further includes at least one additional buffer or cap layer disposed between the exciton blocking electronic filter and the cathode. In some embodiments, the at least one capping layer is at least LUMO _EC or less than 0.3 eV less than LUMO _EC (eg, less than 0.2 eV) to conduct electrons to the cathode. Has a LUMO energy level. In some embodiments, the LUMO energy level of the cap layer is greater than the LUMO _{EC in} the range of 0.5 eV, for example, greater in the range of 0.4 eV, greater in the range of 0.3 eV, and greater than 0.2 eV. Large within range. In some embodiments, the cap layer has a LUMO energy level that is 0.1 eV less or greater than the LUMO _EC . In some embodiments, at least one cap layer is selected from a fullerene and a functionalized fullerene derivative. In some embodiments, at least one cap layer comprises PTCBI.

  In some embodiments, the cap layer includes a material having a LUMO energy level that does not promote conduction of electrons to the cathode. In these embodiments, the cap layer may be thin enough to transport electrons through the damage-inducing state. In some embodiments, at least one cap layer includes a material selected from BCP, BPhen, UGH-2, and CBP.

  In some embodiments, at least one cap layer and at least one electron conducting material comprise the same material. In some embodiments, at least one cap layer, at least one electron conducting material, and at least one acceptor material comprise the same material.

  In some embodiments, the at least one cap layer and the at least one cathode side wide energy gap material comprise the same material.

An exciton blocking hole filter is disposed between the anode and the at least one donor material and includes a mixture comprising at least one anode side wide energy gap material and at least one electron conducting material. At least one anode side wide energy gap material
The highest occupied orbital energy level (HOMO _AS-WG ) which is equal to or higher than HOMO _Don ;
The lowest unoccupied orbital energy level (LUMO _AS-WG ) that is equal to or less than LUMO _Don or is larger than LUMO _Don within a range of 0.3 eV;
- it has an energy gap of _HOMO Don _-LUMO wide _HOMO AS-WG _-LUMO than the energy gap of _{Don AS-WG,} a.

The at least one hole-conducting material has a highest occupied orbital energy level (HOMO _HC ) that is less than or equal to HOMO _Don (closer to vacuum) or greater than HOMO _Don within 0.2 eV (farther from vacuum). Have.

  In order to extend the operating life of the device by using morphologically stable materials, some embodiments of the present invention may require, for example, higher than the maximum operating temperature of the device, higher than the temperature or temperature range at which the device generally operates. A wide energy gap material on the anode side is used that has a sufficiently high glass transition temperature, such as high, above a threshold temperature.

In some embodiments, the HOMO _AS-WG is greater than the HOMO _Don , eg, at least 0.2 eV greater, at least 0.3 eV greater, at least 0.5 eV greater, at least 1 eV greater, at least 1.5 eV greater, or at least 1.5 eV greater. The LUMO _AS-WG is 2 eV higher and the LUMO _AS-WG is lower than the LUMO _Don , for example, at least 0.2 eV lower, at least 0.3 eV lower, at least 0.5 eV lower, at least 1 eV lower, at least 1.5 eV lower, or at least 2 eV lower.

In some embodiments, HOMO _HC is equal to HOMO _Don .

In some embodiments, HOMO _HC is less than HOMO _Don , for example, less than 0.5 eV, less than 0.4 eV, less than 0.3 eV, or less than 0.2 eV. Small within range.

In some embodiments, HOMO _HC is 0.1 eV less or greater than HOMO _Don .

In some embodiments, the HOMO _AS-WG is greater than the HOMO _HC , for example, at least 0.2 eV greater, at least 0.3 eV greater, at least 0.5 eV greater, at least 1 eV greater, at least 1.5 eV greater, or at least 1.5 eV greater. 2 eV larger.

In some embodiments, the HOMO _AS-WG is greater than HOMO _{Don by} more than 0.2 eV, for example, greater than 0.3 eV, greater than 0.5 eV, greater than 1 eV, and 1. It is larger than 5 eV or larger than 2 eV.

  In some embodiments, the at least one anode-side wide energy gap material is N, N'-diphenyl-N, N'-bis (1-naphthyl) -1-1'-biphenyl-4,4'-. Tetraarylbenzidines such as diamine (NPD) and N, N'-bis- (3-methylphenyl) -N, N'-bis- (phenyl) -benzidine (TPD), triarylamine, 5,10-disubstituted Including materials selected from anthracene, oligothiophene, 9,9-dialkyl-fluorene and oligomers thereof, 9,9-diaryl-fluorene and oligomers thereof, oligophenylene, spiro-biphenyl and substituted derivatives thereof, and derivatives thereof.

For example, higher than the temperature or temperature range the device operates in general, higher than the highest operating temperature of the device, has a sufficiently high T _g of the like above the temperature threshold, by using the anode side of the wide energy gap materials, devices May be increased in operating life. For example, in some embodiments, the at least one anode-side wide energy gap material is 3,3 ′, 5,5′-tetra [(m-pyridyl) -phen-3-yl] biphenyl (BP4mPy), 2,2 ′, 2 ″-(1,3,5-benzintriyl) -tris (1-phenyl-1-H-benzimidazole) (TPBi), bis (2-methyl-8-quinolinolate) -4- (Phenylphenolato) aluminum (BAlq), tris (8-hydroxy-quinolinato) aluminum (Alq3), tris (2,4,6-trimethyl-3- (pyridin-3-yl) phenyl) borane (3TPYMB), , 40- (1,3-phenylene) bis (2,6-di-tolylpyridine-3,5-dicarbonitrile) (m-MPyCN), 4,40- ( , 3-Phenylene) bis (2,6-di (biphenyl-4-yl) pyridine-3,5-dicarbonitrile) (m-PhPyCN), 4,40- (1,3-phenylene) bis (2 6-diphenylpyridine-3,5-dicarbonitrile) (m-PyCN), 6,60- (1,4-phenylene) bis (2-phenyl-4-p-tolylnicotinonitrile) (p-PPtNN) 4,40- (1,4-phenylene) bis (2-phenyl-6-p-tolynicotinonitrile) (p-PPtNT), tris (6-fluoro-8-hydroxy-quinolinato) aluminum (6FAlq3), 2,6-bis (4-cyanophenyl) -4-phenylpyridine-3,5-dicarbonitrile (CNPyCN), 4,40- (1,4-phenylene) bis (2,6-di- Rylpyridine-3,5-dicarbonitrile) (p-MPyCN), bisbenzimidazo [2,1-a: 1 ′, 2-b ′] anthra [2,1,9-def: 6,5,10- d'e'f '] diisoquinoline-10,21-dione (PTCBI), 5,10,15-tribenzyl-5H-diindolo [3,2-a: 3', 2'-c] carbazole (TBDI), 5,10,15-triphenyl-5H-diindolo [3,2-a: 3 ′, 2′-c] carbazole (TPDI), 1,3-bis [3,5-di (pyridin-3-yl) Phenyl] benzene (BmPyPhB), 1,3,5-tri (m-pyridin-3-ylphenyl) benzene, 1,3,5-tris (3-pyridyl-3-phenyl) benzene, 3,3 ′-[ 5 '-[3- (3-pyridinyl) phenyl] [1, ': 3', 1 "-terphenyl] -3,3" -diyl] bispyridine (TmPyPB), 9,9-dimethyl-10- (9-phenyl-9H-carbazol-3-yl) -9,10- Material selected from dihydroacridine (PCZAC), 3,3-di (9H-carbazol-9-yl) biphenyl (mCBP), 4,40-bis (triphenylsilyl) -biphenyl (BSB), and derivatives thereof including.

  In some embodiments, the glass transition temperature of the wide energy gap material on the anode side is 85 ° C or higher, 95 ° C or higher, 105 ° C or higher, 115 ° C or higher, 125 ° C or higher, 135 ° C or higher, 145 ° C or higher, 155 ° C. The temperature is 165 ° C or more, 175 ° C or more, 185 ° C or more, 195 ° C or more, 200 ° C or more, 225 ° C or more, or 250 ° C or more.

  In some embodiments, the glass transition temperature of the wide energy gap material on the anode side is between 85-200C, between 90-195C, between 95-190C, between 100-185C, between 105-185C. Between 180C, between 110-175C, between 115-170C, or between 120-165C. It should be noted that materials having a glass transition temperature higher than 200C, for example between 200-300C, 200-275C, 200-250C, or 200-225C, may be used.

The operating temperature of the device changes and depends on many factors, for example, ambient conditions (such as temperature and light intensity) and whether an enhancement mechanism (such as a solar concentrator) is used with the device. Can. For example, the ambient temperature may change depending on the geographic location, time, time, etc. of the device. Similarly, light intensity may also depend on geographic location, time of day, time of day, cloud cover, angle of incidence and other factors. Thus, in some embodiments, the wide energy gap material on the anode side may, for example, provide a device under normal ambient conditions that is higher than the temperature or temperature range at which the device typically operates (eg, at normal ambient conditions). having, such as higher than the highest operating temperature, a sufficiently high T _g.

In some embodiments, a solar concentrator may be integrated with or used with the device to increase, enhance, or enhance the light directed to the device. The use of concentrators and / or other intensifying mechanisms can increase the operating temperature of the device beyond that experienced by the device under normal ambient conditions. Thus, to increase the stability and operating life of the device, the wide energy gap material on the anode side may have a _Tg higher than the maximum operating temperature experienced by the device under enhanced lighting conditions.

  In some embodiments, the at least one donor material is a phthalocyanine, such as copper phthalocyanine (CuPc), chloroaluminum phthalocyanine (ClAlPc), tin phthalocyanine (SnPc), zinc phthalocyanine (ZnPc) and other modified phthalocyanines, boron. Subphthalocyanines such as subphthalocyanine (SubPc), naphthalocyanines, merocyanine dyes, boron dipyrromethene (BODIPY) dyes, thiophenes such as poly (3-hexylthiophene) (P3HT), low band gap polymers, polyacenes such as pentacene and tetracene, diene Selected from indenoperylene (DIP), squaraine (SQ) dye, tetraphenyldibenzoperiflanthene (DBP), and derivatives thereof Including the fee. Examples of squaraine donor materials are 2,4-bis [4- (N, N-dipropylamino) -2,6-dihydroxyphenyl] squaraine, 2,4-bis [4- (N, N- Diisobutylamino) -2,6-dihydroxyphenyl] squaraine and 2,4-bis [4- (N, N-diphenylamino) -2,6-dihydroxyphenyl] squaraine (DPSQ). Not limited.

  In some embodiments, the at least one hole conducting material is a phthalocyanine such as copper phthalocyanine (CuPc), chloroaluminum phthalocyanine (ClAlPc), tin phthalocyanine (SnPc), zinc phthalocyanine (ZnPc), and other modified phthalocyanines. , Subphthalocyanines such as boron subphthalocyanine (SubPc), naphthalocyanines, merocyanine dyes, boron dipyrromethene (BODIPY) dyes, thiophenes such as poly (3-hexylthiophene) (P3HT), low band gap polymers, polyacenes such as pentacene and tetracene , Diindenoperylene (DIP), squaraine (SQ) dye, tetraphenyldibenzoperiflanthene (DBP), and derivatives thereof Including the material. Examples of squaraine donor materials are 2,4-bis [4- (N, N-dipropylamino) -2,6-dihydroxyphenyl] squaraine, 2,4-bis [4- (N, N- Diisobutylamino) -2,6-dihydroxyphenyl] squaraine and 2,4-bis [4- (N, N-diphenylamino) -2,6-dihydroxyphenyl] squaraine (DPSQ). Not limited.

  In some embodiments, at least one donor material and at least one hole conducting material comprise the same material. In some embodiments, the at least one donor material and the at least one hole conducting material include different materials.

  In some embodiments, the mixture comprises at least one anode-side wide energy gap material and at least one hole conducting material in a volume ratio of about 10: 1 to 1:10, for example, in a volume ratio of about 8: 1-1: 8, about 6: 1 to 1: 6 by volume ratio, about 4: 1 to 1: 4 by volume ratio, or about 2: 1 to 1: 2 by volume ratio. In some embodiments, the ratio is about 1: 1. It should be understood that the specified ratios include integer and non-integer values.

  In some embodiments, the device further includes at least one additional buffer or cap layer disposed between the exciton blocking hole filter and the anode.

  The organic photosensitive optoelectronic devices disclosed herein can be created and placed on any substrate that provides the desired structural properties. Thus, in some embodiments, the device further includes a substrate. For example, the substrate may be flexible or rigid, planar or non-planar. The substrate can be transparent, translucent, or opaque. The substrate may be reflective. Plastic, glass, metal, and quartz are examples of solid substrate materials. Plastic foil, metal foil and thin glass are examples of flexible substrate materials. The material and thickness of the substrate may be selected to obtain desired structural and optical properties.

  The organic photosensitive optoelectronic device of the present disclosure may act as a PV device, such as, for example, a solar cell, photodetector or photoconductor.

  When the organic photosensitive optoelectronic device described herein acts as a PV device, the materials used in the photoconductive organic layer and their thickness may be such as to optimize the external quantum efficiency of the device. , May be selected. For example, an appropriate thickness may be selected to achieve a desired light spacing in the device and / or to reduce resistance in the device. If the organic photosensitive optoelectronic device described herein acts as a photodetector or photoconductor, the materials used in the photoconductive organic layer and their thickness may be, for example, the device for a desired spectral region. May be selected to maximize the sensitivity of

  And the device may further include at least one smoothing layer. The smoothing layer may be located, for example, between the photoactive layer and one or both of the electrodes. A membrane containing 3,4-polyethylenedioxythiophene: polystyrene sulfonate (PEDOT: PSS) is an example of a smooth layer.

  The organic photosensitive optoelectronic device of the present disclosure may exist as a series device including two or more subcells (series device). A subcell, as used herein, refers to a component of a device that includes at least one donor-acceptor heterojunction. When the subcell is used individually as a photosensitive optoelectronic device, it typically includes a set of electrodes. Series devices may include a charge transport material, an electrode, or a charge recombination material or tunnel junction between the series donor-acceptor heterojunctions. In some tandem structures, adjacent subcells can use shared materials (ie, shared electrodes, charge transport regions, or charge recombination regions). In other cases, adjacent subcells do not share a common electrode or charge transport region. The subcells may be electrically connected in parallel or in series.

In some embodiments, the charge transport layer or charge recombination _{layer, Al, Ag, Au, MoO} 3, Li, LiF, Sn, Ti, WO 3, indium tin oxide (ITO), tin oxide (TO) , Gallium indium tin oxide (GITO), zinc oxide (ZO) or zinc indium tin oxide (ZITO). In other embodiments, the charge transport layer or charge recombination layer may be composed of metal nanoclusters, nanoparticles or nanorods.

  According to another embodiment, a device of the present disclosure is an excitation device disposed between a first subcell and a second subcell of a device including two or more subcells, as described herein. An electron blocking charge carrier filter may be included. As an example, a schematic diagram of an organic series photosensitive optoelectronic device according to the present disclosure is shown in FIG. The electrode 110 includes an anode or a cathode. Where electrode 110 includes a cathode, electrode 140 includes an anode. When electrode 110 includes an anode, electrode 140 includes a cathode. The series device includes two photoactive regions 150 and 160. Each of these regions includes donor and acceptor organic materials, and may form a donor-acceptor heterojunction as described herein.

  In device A of FIG. 29, layer 115 is an exciton blocking electron filter as described herein. In some embodiments, layer 115 may be an exciton blocking hole filter as described herein. Layer 115 is located between photoactive region 150 and photoactive region 160 of the subcell. In yet another embodiment, the series device may include an additional exciton blocking charge carrier filter, as shown in device B of FIG. For example, a series photosensitive device may include two charge carrier filters located between subcells. In this structure, if the exciton blocking charge filter 115 is an exciton blocking hole filter, the exciton blocking charge filter 135 is an exciton blocking electron filter, and vice versa. In addition, the series device may further include an exciton blocking charge carrier filter disposed between the photoactive region and the electrode, such as between the photoactive region 150 and the electrode 140.

  Although not shown in FIG. 29, devices A and B may further include additional isolation layers located between the subcells. The separation layer may include at least one electrode, at least one charge transport layer, or at least one charge recombination layer. For example, in device A, the separation layer may be disposed between the exciton blocking charge filter 115 and either the photoactive region 150 or the photoactive region 160, and optionally, the exciton blocking charge filter 115. And adjacent. In some embodiments, the separation layer is a charge recombination layer, as is known in the art or as described herein.

  As a further example, in device B, the separation layer may be located between the exciton blocking charge filter 115 and the exciton blocking charge filter 135, and optionally with one or both of layer 115 and layer 135. Adjacent. In some embodiments, the separation layer is a charge recombination layer, as is known in the art or as described herein.

  As shown, in the device A of FIG. 29, when the charge recombination layer is disposed between the layer 115 and the photoactive region 150, and when the electrode 110 includes a cathode, the layer 115 And an exciton blocking hole filter that blocks holes and conducts holes from the photoactive region 160 to the charge recombination layer.

  Alternatively, in the same structure except where electrode 110 is the anode, layer 115 may be an exciton blocking electron filter that blocks excitons and conducts electrons from photoactive region 160 to the charge recombination layer. .

  Also, the series device may include two or more exciton blocking charge filters located between the subcells, as shown in device B of FIG. When the charge recombination layer is disposed between layer 115 and layer 135, and when electrode 110 includes a cathode, layer 135 blocks excitons and transfers photoactive region 160 to charge recombination layer. An exciton blocking hole filter that conducts holes may be used. Layer 115 may be an exciton blocking electron filter that blocks excitons and conducts electrons from photoactive region 150 to the charge recombination layer.

  Alternatively, in the same structure except when electrode 110 is the anode, layer 135 may be an exciton blocking electron filter that blocks excitons and conducts electrons from photoactive region 160 to the charge recombination layer. . Layer 115 may be an exciton blocking hole filter that blocks excitons and conducts holes from photoactive region 150 to the charge recombination layer.

  An advantage of the present disclosure is that the exciton blocking charge carrier filter may be transparent because it uses a wide energy gap material. By mixing the transparent wide energy gap material with the electron or hole conducting material, the electron or hole conducting material is sufficiently diluted to make the exciton blocking charge carrier filter transparent at the relevant wavelength. I do. An exciton blocking charge carrier filter is said to be "transparent" if it transmits at least 50% of the incident electromagnetic radiation at the relevant wavelength. In some embodiments, the filter transmits at least at least 60%, at least 70%, at least 80%, at least 90%, or about 100% of the incident electromagnetic radiation at the relevant wavelength. A charge carrier filter is said to be optically lossless if it absorbs little (<1%) electromagnetic radiation at the wavelength of interest.

In various embodiments, the device may use one or more buffer layers, which are preferably transparent over the visible spectrum. A buffer layer for collecting / transporting charges may be, for example, between the photoactive region and the corresponding electrode. Also, a buffer layer for collecting / transporting charge may be located, for example, between the separation layer and the photoactive region. In some embodiments, the charge collecting / transporting layer comprises a material selected from metal oxides. In certain embodiments, the metal oxide _is selected from _{MoO 3, V 2 O 5,} ZnO and TiO _2.

  Layers and materials may be laminated using techniques well known in the art. For example, the layers and materials described herein can be laminated or co-laminated from a solution, a vapor, or a combination of both. In some embodiments, the organic material or layer is formed by solution processing, for example, one or more techniques selected from spin coating, spin casting, spray coating, dip coating, doctor blading, inkjet printing or transfer printing. For example, they can be laminated or co-laminated.

  In other embodiments, the organic materials may be laminated or co-laminated using vacuum thermal evaporation, for example, using vacuum evaporation, organic vapor deposition, or organic vapor jet printing.

  Exciton blocking charge carrier filters of the present disclosure, including mixtures of materials, may be made by varying the conditions of the stack. For example, the concentration of each material in the mixture can be controlled by changing the rate of lamination of each material.

  It should be understood that the embodiments described herein may be used in connection with a wide variety of structures. Functional organic photovoltaic devices may be achieved by combining the various layers described in different ways, or the layers may be omitted altogether, based on design, performance and cost factors. Is also good. Also, additional layers not specifically described may be included. Materials other than those specifically described may be used. The names given to the various layers herein are not intended to be strictly limiting.

  Unless otherwise specified, or unless otherwise specified, all numbers used in the specification and claims, which indicate the amounts of components, reaction conditions, and analytical measurement results, refer to the term `` about '' in all cases. "Should be understood as modified by". Thus, unless otherwise indicated, numerical parameters set forth herein and in the appended claims are approximate, which may vary depending on the desired properties sought to be obtained by the present disclosure. At least not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter should be construed in light of the significant figures and numbers approximated by conventional rounding techniques.

  Unless stated otherwise, numerical values set forth in specific examples are recorded as accurately as possible, even though the numerical ranges and parameters set forth in the broader ranges of this disclosure are approximate. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in the measurements of their respective tests.

  The devices and methods described herein are further illustrated by the following non-limiting examples, which are for illustrative purposes only.

(Example)
(Example 1)
C ₆₀ and bathocuproine a (BCP) were mixed at various concentrations, to form an exciton blocking electronic filters. BCP _has (singlet of 1.86 eV, triplet of 1.55 eV) C 60 and higher singlet (3.17EV) and triplet (2.62 eV) energy, and LUMO (-1.6eV) a wide energy gap material, the BCP inert dopant, prevent movement of both energy and electrons from C _60. The doped C ₆₀ : BCP film effectively blocks excitons while still conducting electrons. Based on these properties, a doped film was utilized as a buffer layer / filter that provided improved device performance compared to devices containing other buffers.

The effect of absorption of BCP doped into fullerene was examined by preparing C ₆₀ : BCP films at various volume ratios. FIG. 2 shows the absorption spectra of the pure C ₆₀ film and the doped C ₆₀ film. When the ratio of C ₆₀ is reduced, the absorption is reduced, approaching the absorption of BCP. However, as shown in the inset of FIG. 2, the decay of the two absorption peaks at 340 nm and 450 nm, corresponding to Frenkel exciton and charge transfer (CT) exciton, respectively, took quite different rates. Extinction coefficient of allowable Frenkel transition in 340nm reflects the nature of the monolayer of the transition, as predicted by Beer's law was consistent with the linear attenuation with a ratio of C _60. Interestingly, the extinction coefficient of the CT absorption between molecules in 450 nm, shows an exponential decay, and conforming to the formula alpha ^{= x -2.4} where the x and the volume ratio of _{C 60.} This meant that the formation of CT excitons was accompanied by a few molecules. The absorption spectrum of the C ₆₀ : BCP film showed that the doping concentration had a significant effect on CT excitons, and suppressed formation even at moderate doping levels.

(Example 2)
The device was made as follows. Glass substrate covered with patterned ITO (patterned stripe has a width of 2 mm, thickness = 150 nm ± 10 nm, sheet resistance = 20 ± 5 Ωcm ⁻² , transmittance is 84% at 550 nm, courtesy of Thin Film Devices) Was washed with soap and boiled (5 min each) in tetrachloroethylene, acetone and propanol. Immediately before loading the ITO substrate into the inside of the high vacuum chamber, the substrate was exposed to an ozone atmosphere (UVOCS T10X10 / OES) for 10 minutes. The speed of laminating the layers of the pure material is as follows: MoO _x (0.02 nm / s), NPD (0.1 nm / s), C ₆₀ (0.1 nm / s), BCP (0.1 nm / S) and Al (0.2 nm / s). The deposition rate of the doped film (C ₆₀ : BCP volume content) is as follows. In the case of C ₆₀ : BCP (2: 1), C ₆₀ (0.08 nm / s): BCP (0 .04 nm / s), and in the case of C ₆₀ : BCP (1: 1), a co-layer of C ₆₀ (0.06 nm / s): BCP (0.06 nm / s), and C ₆₀ : BCP In the case of (1: 2), a co-layer of C ₆₀ (0.04 nm / s): BCP (0.08 nm / s) was used. After lamination of the organic layer, the mask having a stripe width of 2mm was placed on a substrate under N _2, was laminated an Al cathode of 100 nm. The device area was 4 mm ² .

In order to observe the distinct photoreactive from C _60, a hole transport material in a wide gap, N, N'-di - [(1-naphthyl) -N, N'-diphenyl] -1,1 A double layer device having the structure shown in FIG. 3 was prepared using '-biphenyl) -4,4'-diamine (NPD) as a donor. All changes observed between the devices, instead of the interface effect, as related to the volume of the doped membrane, pure layer of C ₆₀ in D / A joint surface is thermodynamically and kinetics of charge separation It was intended to protect.

FIG. 3 shows the current-voltage (JV) characteristics and the external quantum efficiency (EQE) curve of the device under quasi-AM1.5G irradiation having an intensity of 1 sun (100 mW / cm ² ). As shown in Table 1, as the doping concentration of the C ₆₀ : BCP layer increases from 1: 0 to 1: 2, the short circuit current (J _SC ) increases from 3.0 ± 0.1 mA / cm ² to 1 become a .3 ± 0.1mA / cm ^2, it was reduced by about 1.7mA / cm ^2. This reduction, as reflected in the measurement results of EQE, is due to the decrease in the photoreaction of the C _60, on the other hand, as the ratio of C ₆₀ is reduced, the open circuit voltage (V _OC) is 0 The fill factor (FF) increased from 0.45 ± 0.01 to 0.49 ± 0.01, remaining largely unchanged at 0.87 ± 0.01. Reduction reactions of EQE is reduced reaction between 400nm~550nm is, they produce more rapidly than the reaction at a wavelength shorter than 400 nm, and the profile of the absorption of doped _{C 60} films, there was significantly correlated. The effect of CT excitons can be most clearly confirmed by comparing D1 and D2. In these devices, the response of the EQE at 350 nm remained unchanged, while the response of the EQE at 450 nm decreased from 23% to 15.5%, about a third.

The observation that the photoreaction decreases with increasing concentration of BCP doping in the mixed layer is demonstrated by the dilution of SubPC using the wide energy gap material UGH2, which resulted in a significant increase in photocurrent, J. et al. Nat. Mater. This was in sharp contrast to the observations of Menke et al. In the case of SubPc, Menke reported that the increase in photocurrent was due to the increase in exciton diffusion length caused by the fact that there was a type of concentration where the Forster radius increased faster than the average molecular separation distance. The cause was shown. The increase in diffusion length was attributed to increased photoluminescence efficiency, excited state duration and spectral overlap integral, and reduced nonradiative decay rates in the doped films. The contrast between these results can be explained by examining the exciton origin for the two systems. In SubPc, a monomolecular forster exciton was formed. In the dilution, the decrease in absorption was linear while the increase in exciton diffusion length was exponential. Conversely, in the C ₆₀ is, CT excitons were present, which is formed by a multi-molecular quite a few. In the dilution, this resulted in an exponential decay of CT exciton formation, outweighing any increase in diffusion length. Absorption characteristics of CT in C ₆₀ is, by the fact that in a region of high solar irradiance, the overall performance of the device is decreased.

While the mixed device had low photocurrent, the _VOC of the device remained unchanged, indicating that maintaining the D / A interface achieved its desired effect. In dilutions of C _60, the fact that the FF did not decrease, showing that the mixed film could be efficiently transporting electrons. J _SC in combination with reduced, the increase in _{V OC} and FF does not change in dilutions, resulted in a greater than 50% reduction in power conversion efficiency (eta), 0.56% from 1.14% (D1) (D4). However, an increase in the transparency of the mixed film, and transport of efficient charge, C _60: BCP membrane is attractive candidates for the buffer layer.

(Example 3)
The device shown in FIG. 4 was manufactured by the manufacturing method disclosed in Example 2. FIG. 4 shows the JV curve of the device under 1 sun, AM1.5G irradiation and a plot of external quantum efficiency as a function of wavelength, with the device structure (x = 10 nm (D7), 20 nm) in the inset. (D6), shown with 30 nm (D5) Table 2 provides performance data for this device.

(Example 4)
The device shown in FIG. 5 was manufactured by the manufacturing method disclosed in Example 2. FIG. 5 shows the JV curve of the device under 1 sun, AM1.5G irradiation and a plot of the external quantum efficiency as a function of wavelength, with the device structure (x = 0 nm (D8), 20 nm) in the inset. (D9), 40 nm (D10)). Table 3 provides performance data for this device.

(Example 5)
An OPV device shown in FIG. 6 (inserted figure below) was produced. Two _{C 60} layer (the one hand, a x ≦ 35 nm thick and the other, [40 nm-x] thickness is) is sandwiched between, the 10nm thick _BCP: the OPV comprising _{C 60} layers, red absorbing donor It was prepared using (2,4-bis [4- (N, N-diphenylamino) -2,6-dihydroxyphenyl] squaraine) (DPSQ). Pure _{C 60} and _BCP: total thickness of the _{C 60} film was 50nm. FIG. 6 shows the JV and EQE characteristics of devices D20 to D23 having x = 5 nm to 35 nm, and other performance parameters are shown in Table 4. _BCP: As _{C 60} layer moves toward the D / A joint surface (i.e., as x _{decreases), J SC} is, 6.2 ± 0.3mA / cm ² from 4.1 ± 0.2 mA / cm ² . This trend, as the thickness of the pure _{C 60} layer adjacent to the D / A joint surface is reduced (D20～D23 in Table _4), were seen in the EQE spectrum of the reaction was reduced from _{C 60.} These data, excitons generated in C ₆₀ film adjacent to the metal electrodes, the diffusion in the D / A bonding surface dissociation may occur to free charges, BCP: showed that C ₆₀ is prevented . On the other hand, the mixed layer does not prevent charge transport, as inferred from the constant high FF = 0.72 ± 0.01 and V _OC = 0.94 ± 0.01V. The thickness of the _{C 60} layer adjacent to the D / A joining surface is increased from x = 5 nm to 35 nm, 1 sun, the power conversion efficiency under AM1.5G illumination from 2.7 ± 0.1% Increased to 4.1 ± 0.1%.

(Example 6)
The device shown in FIG. 7 was manufactured by the manufacturing method disclosed in Example 2. FIG. 7 shows the JV curve of the device under 1 sun, AM1.5G irradiation (the inset shows the characteristics of the device) and the external quantum efficiency as a function of wavelength (the inset shows the structure of the device. Is shown). With these devices, the performance of a mixed buffer layer covered with an additional layer to improve charge collection was compared to a single pure PTCBI buffer layer.

(Example 7)
The device shown in FIG. 8 was manufactured by the manufacturing method disclosed in Example 2. FIG. 8 shows the external quantum efficiency under applied bias (+0.5 V for dashed line, -1 V for solid line), normalized to EQE at zero bias, for various buffer layers. These data indicate that the mixed buffer layer reduced the bias dependence of the device and reduced charge storage at the active layer / buffer interface, resulting in a reduced amount of exciton-polaron quenching. showed that.

(Example 8)
The mechanism by which the mixed layer rejects excitons can be evaluated in a statistical manner, in which the reduced density of states used in the doped layer reduces the rate of exciton migration. In the mixed layer, there is a significantly reduced number of states to which energy can be transferred, effectively preventing those processes. The effect of the change in the density of states is modeled by Monte Carlo simulation, and the result can be confirmed in FIG. In this model, excitons were generated randomly in a pure film adjacent to the mixed film. Then, in order to simulate the diffusion, the excitons were moved by a random walk for a predetermined number of steps, and their final positions were recorded. Excitons were assumed to move only by nearest hopping. At the interface between the doped and pure layers, the probability of hopping between the layers was measured by the relative number of sites used in each layer. The model predicted that for the junction between two materials with equal site density, 50% of the excitons had diffused into the buffer. 1: 1 _C 60: corresponding to the case of Frenkel exciton _{C 60} approaching the buffer of BCP, if 50% of the sites in the buffer is reduced, only 20% of the excitons is moved. Simulating the case of a CT exciton approaching a 1: 1 C ₆₀ : BCP buffer at 80% site reduction, less than 5% of the excitons migrated. These simulations, while only considering statistical measures, showed that the doped buffer blocked excitons fairly well.

(Example 9)
As shown in FIG. 10, in the upper diagram, the absorption spectrum normalized C ₇₀ covered with different buffer layer was plotted as a function of wavelength. These data indicate that the more the mixture, the higher the exciton energy, which helps in exciton rejection. The figure below shows the emission spectrum of the quenching layer (NPD), blocking layer (BCP) and mixtures covered with a buffer layer (excited at 450 _{nm) C 70.}

(Example 10)
As shown in FIG. 11, the EQE spectrum of the device covered with various buffer layers (top) and the JV curve of the device under 0.8 sun, AM1.5G irradiation (bottom) are the other. Compared to the buffer layer, an improvement in performance due to the inclusion of the buffer of the compound was shown.

(Example 11)
Investigate the use of a buffer consisting of C ₆₀ : BCP and compare its performance with the performance of the previously developed buffers BCP and PTCBI and the buffer of compounds where the C ₆₀ : BCP is covered with BCP or PTCBI. did. In these devices, and the active layer from DPSQ _{/ C 60.} The structure of the JV, EQE and device is shown in FIG. 12, and the relevant data is shown in Table 5. The _VOC of the device remained constant at 0.95 ± 0.01 V, independent of the buffer. 10nm devices covered with PTCBI buffer (D13) is, the parasitic light absorption from PTCBI ^20, showed 7.1 ± 0.1mA / cm ² is the smallest _{J SC.} Unlike PTCBI, an other buffers having a thickness of 10 nm, BCP (D11) and _C 60: BCP (D12) does not absorb, 7.5 ± 0.1mA / cm ² and 7.6 an increase in _{J SC} to ± 0.1mA / cm ² resulted, respectively. C ₆₀ : BCP / PTCBI (D14) and C ₆₀ : BCP / BCP (D15), buffer layers of compounds having a thickness of 15 nm, are 8.1 ± 0.1 mA / cm ² and 8.3 ± 0. that .1mA / cm ^2, even higher _{J SC} had respectively. Measurement results of the EQE is a change in the reaction of C _60, an increase of J _SC to transition from 10nm buffer to 15nm and it was confirmed that due to optical effects, the optical model using transfer matrix form ^9, It was shown that the change in photocurrent was caused. Significant changes also occurred in FF between devices. BCP-covered devices D11 and D15 exhibited the smallest FFs of 0.64 ± 0.01 and 0.65 ± 0.01, respectively. The buffer consisting of C ₆₀ : BCP only (D12) had a slightly better FF of 0.66 ± 0.01. PTCBI covered devices D13 and D14 showed the largest FFs of 0.68 ± 0.01 and 0.71 ± 0.01, respectively. Due to the increase of the photocurrent and the FF, the power conversion efficiency of the C ₆₀ : BCP / PTCBI buffer is 5.3 ± 0.1%, 5.0 ± 0.1% of C ₆₀ : BCP / BCP, and C ₆₀ : Compared with 4.8 ± 0.1% of BCP, 4.8 ± 0.1% of PTCBI, and 4.8 ± 0.1% of BCP, it was the largest.

By examining the EQE under applied bias and the responsivity (R) as a function of irradiation intensity, the difference in FF between the buffer layers could be explained. FIG. 13 shows the EQE under a -1 V bias, normalized to their 0 V EQE, for devices that include various buffer layers. The signal from the _{C 60} between 400 nm to 550 nm, adjusted by the application of an external bias, on the one hand, DPSQ reaction between 600nm~825nm remained constant. The effect of the buffer layer was confirmed in the magnitude of the deviation from the zero bias EQE. The voltage dependence was greatest for the 10 nm BCP buffer covered device (D11), while it was smallest for the 10 nm C ₆₀ : BCP buffer (D12).

The device (D15) covered with 10 nm C ₆₀ : BCP / 5 nm BCP showed a lower voltage dependence than the 10 nm BCP (D11). This was due to two factors. First, the BCP layer is thinner and reduces the number of trapped electrons. Second, as indicated above, the C ₆₀ : BCP layer prevented excitons from diffusing to the C ₆₀ : BCP / BCP interface while still transporting electrons. This prevented excitons from interacting with electrons trapped at the C ₆₀ : BCP / BCP junction.

10 nm PTCBI buffer _(D13), the transport of electrons of equal energy from _{C 60,} was possible by the adjustment of their LUMO. At the same time, the PTCBI / Ag interface did not form a dipole or energetic barrier for charge extraction. 10 nm C ₆₀ : BCP / 5 nm PTCBI (D14) worked similarly, while also preventing excitons from reaching the PTCBI.

The quenching of polaron-exciton induced excitons was further demonstrated by examining the responsiveness as a function of irradiation intensity, as shown in FIG. Responsiveness was defined as the short circuit current density of the device, divided by the light intensity of the incident area. This parameter made it possible to compare the current generation efficiency of the device under different irradiation intensities. The BCP-covered devices D11 and D15 showed a distinct non-linear decrease in response as irradiation increased from 1 W / m ² (0.01 sun) to 100 W / m ² (1 sun). The non-linearity of the decay was consistent with the exciton-polaron induced quenching of the exciton, and the increased illumination intensity resulted in an increase in the number of both excitons and polarons. All other buffers used for D12, D13 and D14 showed small changes in responsiveness as a function of illumination intensity, indicating reduced exciton-polaron induced exciton quenching.

(Example 12)
To investigate the exciton blocking properties of C ₆₀ : BCP, a device containing a doped C ₆₀ layer sandwiched between two pure C ₆₀ layers was prepared using a red absorbing donor (2,4-bis [4 -(N, N-diphenylamino) -2,6-dihydroxyphenyl] squaraine) (DPSQ) ²⁰ , ²¹ (FIG. 14). The total thickness of the pure C ₆₀ and C ₆₀ : BCP films was constant and only the position of the doped film was moved from the D / A junction to the Ag electrode.

FIG. 14 shows the JV and EQE characteristics of the devices D16 to D19, and Table 6 shows related data. The thickness of the pure _{C 60} layer adjacent to the D / A cemented surface decreases from 35nm to 5 nm _(or, C 60: a BCP layer, is to move to the D / A bonding surface) As the device of the photocurrent Decreased significantly from 6.2 ± 0.1 mA / cm ² to 4.1 ± 0.1 mA / cm ² . This trend is the reaction of from _{(D16~D19) C 60} as the thickness of the pure _{C 60} layer adjacent to the D / A joint surface is reduced is reduced, was also observed in the EQE spectrum. These results indicate that C ₆₀ : BCP effectively prevents excitons generated in the pure C ₆₀ film adjacent to the metal electrode from diffusing to the D / A junction to separate charges. Showed clearly that it acted as an exciton blocking layer. In contrast to its exciton blocking effect, the doped layer exhibited excellent charge conductivity because the FF of the device remained constant at about 0.72 ± 0.01. The V _OC also remained constant at 0.94 ± 0.01. Overall, increasing the thickness of the pure _C60 layer adjacent to the D / A interface from 5 nm to 35 nm increases η from 2.7 ± 0.1% to 4.1 ± 0.1% did.

(Example 13)
FIG. 15 shows the JV curve under 1 sun, AM1.5G irradiation in the upper figure, and the lower figure shows a plot of the external quantum efficiency as a function of wavelength for devices including various buffer layers. These devices showed improved performance due to the inclusion of the mixed buffer layer.

(Example 14)
Figure 16 is a top _view, devices including various buffer layers containing different ratios of _{C 60} pairs BCP, 1 sun, shows the J-V curves under AM1.5G illumination, in the figure below, the external quantum efficiency The plot of is shown. These devices exhibited optimal mixing ratios of 1: 1 by volume.

(Example 15)
Of _MoO 3/54 nm of ITO / 10 nm glass substrate / 100 nm 1: 8 of _DBP: using structure of _{C 70} / buffer / 100 nm of Ag, were prepared device. Figure 17 is a relatively thick, DBP 1 of pure layers of the _{C 70:} about 8 plan mixed OPV cell including an active layer having a volume ratio of, 1 sun, in the pseudo AM1.5G irradiation, irradiated relates J-V ( Upper left), EQE (upper right) and extracted efficiency parameters (lower). Each buffer regarding thickness and _BPhen: the volume ratio of _{C 70,} shown in Table. The best fill factors and efficiencies are for devices that include a mixed buffer that includes an additional BPhen or PTCBI layer between the mixed region and the contact, and that the contact can be used for mixed or bulk heterojunction devices. Showed improvement.

(Example 16)
Of _MoO 3/25 nm of ITO / 5 nm of the glass substrate / 100 nm 1: 8 of _DBP: using structure of _{C 70} / buffer / 100 nm of Ag, were prepared device. Figure 18 is a relatively thin, 1 with pure layer of DBP and _{C 70:} active layer having 8 volume ratio of, and to plan mixed OPV cells containing various buffers, 0.7Sun, in the pseudo AM1.5G illumination , JV for irradiation (top left), EQE (top right) and extracted efficiency parameters (bottom). Each thickness about the buffer and _BCP: the volume ratio of _{C 70,} shown in Table. The best fill factors and efficiencies are for devices that include a mixed buffer that includes an additional BPhen or PTCBI layer between the mixed region and the contact, and that the contact can be used for mixed or bulk heterojunction devices. Improved, indicating that an exponential fill factor could be obtained for mixed layer devices.

(Example 17)
A device was fabricated using the structure specified in FIG. The device in FIG. 19A has a structure of ITO / MoO ₃ / DPSQ / C ₆₀ / C ₆₀ : BPhen (x) / BPhen / Al. The device in FIG. 19B has a structure of ITO / MoO ₃ / DPSQ / C ₆₀ / C ₆₀ : BCP (x) / BPhen / Al. The device in FIG. 19C had a structure of ITO / MoO ₃ / DPSQ / C ₆₀ / C ₆₀ : UGH2 (x) / BPhen / Al. FIG. 19 shows the EQE and JV curves for dilutions with BPhen, CBP and UGH2. Improvement was observed in all cases, reduction in the accumulation of charge in C _{60 /} buffer bonding surface, it was confirmed that resulted in improved.

(Example 18)
OPV cells were produced by vacuum thermal evaporation (VTE) at a reference pressure of 2 × 10 ⁻⁷ torr on glass substrates precoated with indium tin oxide (ITO, sheet resistance: 15 Ω / □). Prior to lamination, the substrates were washed in diluted Tergitol® (type NP-10), deionized water, acetone and isopropyl alcohol and exposed to UV ozone for 10 minutes. The MoO ₃ from Acros Organics _Corp., the _{C 60} from Materials and, Electrochemical Research Corp., a BPhen and DBP from Luminescence Technology _Corp., has acquired the _{C 70} from the SES Research Corporation. _DBP, of _{C 60} and _{C 70,} the temperature gradient sublimation purified once.

A MoO ₃ layer and a BPhen layer were generated at a rate of 0.1 nm / s, and DBP and C ₇₀ were combined with a DBP of 0.02 nm / s lamination rate and a C ₇₀ of 0.16 nm / s lamination rate. To achieve a 1: 8 ratio. _BPhen: The _{C 60} mixed buffer, generated by co-laminating BPhen and _{C 60} at a rate of respectively 0.05 nm / s, 1: produced a mixture of 1. Subsequently, 100 nm thick Ag cathodes were laminated through a shadow mask defining 15 devices and 1 mm diameter devices (0.008 cm ² device area). Following manufacturing, for J-V characteristics and EQE of measurement, in a glove box filled with ultrapure N _2, the device was moved. During the measurements, only the device to be tested was placed under irradiation, while the other devices were stored in the dark. The intensity of the sun simulator, calibrated using a Si standard cell can be traced to NREL, the J _SC, corrected for the spectral mismatch. The EQE as a function of wavelength (l) was obtained using a lock-in amplifier and monochromatic light from a Xe lamp triangulated at 200 Hz. _JSC and PCE errors arise primarily from uncertainties in light intensity and spectral calibration.

Mixed HJ cells were generated by vacuum thermal evaporation (VTE) using the structure MoO ₃ (10 nm) / DBP: C ₇₀ (54 nm, 1: 8 by volume) / buffer / Ag (100 nm). As two different buffer layer, a 8nm thick BPhen (control), covered with pure BPhen layer of 5nm thickness, the 10nm thick _BPhen: (by volume) of _{C 60} 1: 1 in a mixing layer of the ratio Using. FIG. 20 shows the JV characteristics and the EQE spectra of a mixed HJ device with control and compound buffers. As described above, under the irradiation of pseudo AM1.5G, 1 sun (spectral mismatch rate: 1.00 ± 0.01), FF = 55 ± 1% and J _SC = 12.5 ± 0. It had 3 mA / cm ² , V _OC = 0.91 ± 0.1 V and PCE = 6.3 ± 0.3%. The cell containing the buffer of the compound electronic filter showed improvement in all three performance parameters, FF = 63 ± 1%, J _SC = 12.8 ± 0.3 mA / cm ² , V _OC = 0.93 ±. 0.1V and PCE = 7.5 ± 0.4%, the latter corresponding to a 19% increase compared to the control.

The significant improvement in FF for the device containing the compound buffer is shown in FIG. 20 (a) (indicated by the shaded area between the curves), and the energy level diagram is shown in the inset of FIG. 20 (b). . Previous studies have shown that energy level bending occurred at the fullerene / BCP interface, resulting in electron accumulation and large voltage drop, as shown in the inset on the left. As a result, as the voltage is redistributed, the electric field across the active layer decreases, the charge extraction time, and thus the electron and hole at the donor-acceptor heterojunction interface, which had the opportunity for the electrons and holes to recombine. The residence time was increased. In the case of a compound buffer, the high conductivity of the 1: 1 mixture of BPhen: C ₆₀ results in less electron accumulation and therefore a lower voltage drop across the junction (right inset of FIG. 20 (b)). ) And higher electric fields in the DBP: C ₇₀ mixed region. Similarly, this results in reduced bimolecular quenching, resulting in increased FF and increased EQE at wavelengths between l = 400 nm and 550 nm, as shown in FIG. 20 (b). Was.

Both cells showed almost the same EQE at l <400 nm and λ> 550 nm (see FIG. 20 (b)). In lambda <400 nm, by the recombination of reduced bimolecular, while the internal quantum efficiency (IQE) is increased, BPhen: results from C ₆₀ parasitic absorption rate in the mixed buffer, the photoactive region of the cell of the buffer compound Absorption rate decreased. Overall, the EQE of the cells in the compound buffer was approximately equal to the control cells. At λ> 550 nm, the exciton generated in the mixed region of DBP: C ₇₀ almost immediately dissociates into charges, so that the peak of the absorbed optical power moves toward the anode similarly to the peak of the charge distribution. did. This reduced the number of holes at the DBP: C ₇₀ / BPhen junction where electrons are stored (close to the cathode side) in the control cell, while at the same time improving the extraction of holes. Spatial separation of holes and electrons at longer excitation wavelengths reduced the recombination of the two molecules in the control cell and also resulted in nearly identical EQE.

To understand the role of bimolecular recombination, the response (R) for both cells was examined as a function of light intensity (I). The control cell has a monotonic decrease in R with I, from R = 12.7 ± 0.4 A / W at I = 0.6 sun to 11.8 ± 0.3 A / W at I = 2.7 sun. Whereas, for the compound buffer cell, R decreased by 0.2 A / W over the same intensity range (see FIG. 21). Generally, J _SC = J _G -J _MM -J _BM , where J _G is the photogenerated current density, J _MM is the recombination current density of a single molecule, and J _BM is the recombination current density of a bi molecule. Both J _G and J _MM are linearly proportional to I, while J _BM ∝γ ・ n ・ p∝b ・ I ² , where γ is the Langevin coefficient and b is a constant. Therefore, R = J _SC / I = R ₀ −β · I, where R ₀ is the responsiveness in the absence of recombination of two molecules. A linear fit to this analysis (dashed line in FIG. 21) obtained R ₀ = 12.9 A / W for both cells. Identical sections for both cells at zero light intensity indicated that both OPV cells had the same responsiveness as I → 0 in the absence of bimolecular recombination. However, β for control was 4 times greater than β for cells containing the buffer of compound. The smaller β for the compound buffer cell means that the recombination of the bimolecular was only 25% of that of the control cell, and the increased electric field in the mixing region caused the electron and hole concentrations to decrease On average, each of them decreased by about 50%. With respect to the applied external bias, over the heterojunction in the cell of the compound buffer, this internal field, which was larger compared to the control internal field, resulted in improved charge extraction and thus higher FF.

The charge transport properties of the compound buffers were further investigated by 3D Monte Carlo simulation of the layers, programmed in Matlab. Involves the transfer of caused by electrons to re-adjacent hopping between the molecules of C _60, a random distribution of molecules of BPhen and C ₆₀ in solid lattice, was modeled buffer. In this model, the interaction of the columbium between the charges was ignored, the lattice sites were assumed to be of equal energy, and the energy difference provided by the applied electric field was excluded. The likelihood of migration was calculated by Miller-Abrahams theory, which obtains the average extraction time for the charge injected on one side of the buffer layer. The mobility of the layer is then calculated from the relationship between the extraction time and the electric field, and the mobility of the zero electric field of the electrons in the pure _C60 layer is set to 5.1 × 10 ⁻² cm ² / V. -Normalized to the experimental value of s. For a 1: 1 mixed buffer, the model predicted an effective mobility of 4.7 × 10 ⁻³ cm ² / V · s, an order of magnitude lower than that of pure C ₆₀ . By comparison, the pure BPhen film had a significantly lower electron mobility of 1.9 × 10 ⁻⁵ cm ² / V · s, resulting in charge accumulation at the buffer interface that enhanced quenching.

The model was analyzed by examining the predictions for different thicknesses of the 1: 1 mixed buffer, and the results are shown in FIG. 22 (a). Assuming a constant charge density (ie, a constant irradiation intensity), there is a linear relationship between the extraction time (corresponding to the mobility of the film) at the supply voltage and the thickness of the mixed layer, in other words the series resistance. It was confirmed that there was a linear increase in The fit of the mixed buffer to the experimental data for DBP: C ₆₀ OPV is shown in the inset of FIG. The pure BPhen layer conducted electrons through defect states induced during metal deposition, resulting in a super-linear relationship between thickness and resistance. On the other hand, the resistance of the mixing buffer, increases linearly with the thickness of even 20 nm, electrons in the mixed buffer, the C ₆₀ in the mixture showed that it was mainly conducted.

1 on quartz: 1 _BPhen: a 40nm thick _{C 70} film covered with a mixture of _{C 60,} using a photoluminescence (PL) excitation spectra, the efficiency of blocking excitons was investigated experimentally. By comparing the PL intensity of the layers stacked on the surface of the mixture under consideration with the PL intensity of either the "perfect" blocking or quenching layer, the relative importance of these processes could be confirmed. . Therefore, for this purpose, an 8 nm thick BPhen layer or an N, N′-diphenyl-N, N′-bis (1-naphthyl) -1-1-1′-biphenyl-4,4′diamine (NPD) layer is used for this purpose. , As a complete exciton blocking layer or quenching layer. PL intensity of mixing buffer is substantially same and (see FIG. 22 (b)) and seen strength with respect to the reference of the blocking layer, BPhen: mixed layer of C ₆₀ is shown that could be prevented efficiently excitons Was. BPhen: mixture of C ₆₀ is, because of its relatively high electron mobility, mixing the buffer layer acts as an effective filter, excitons and polarons can spatially separated excitation inside the pure fullerene layer Child-polaron resulted in reduced quenching.

(Example 19)
An OPV cell containing a hybrid planar mixed heterojunction (PM-HJ) was made by the experiment disclosed in Example 18. In OPV cells, the DBP and _{C 70,} used respectively as donor and acceptor. The OPV cell has a device structure of indium tin oxide (ITO) / MoO ₃ (10 nm) / DBP: C ₇₀ (54 nm, 1: 8 by volume ratio) / C ₇₀ (9 nm) / buffer / Ag (100 nm). did. _DBP: In PM-HJ OPV cells _{C 70,} three different buffer layers in the following, (1) 8 nm thick bathophenanthroline (BPhen) (control), (2) 10nm thick _BPhen: 1 of _{C 60:} 1 of A mixed layer of ratio, (3) the same mixed buffer as (2) covered with a 5 nm thick pure BPhen layer was used.

  FIG. 23 compares the performance of the devices using the buffer layer structures (1) to (3), and shows the characteristics of the current density (JV) with respect to the voltage and the EQE spectrum as the external quantum efficiency. This is shown together with the summary of Table 7.

The control cell had an FF = 56% and a short circuit current J _SC = 13.8 ± 0.4 mA / cm ² corresponding to the previous result or slightly better than the previous result ¹ . Therefore, the control cell showed a power conversion efficiency PCE = 7.1 ± 0.2% under irradiation of pseudo AM1.5G and 1 sun. Compared to the control cell, the cell containing only the BPhen: C ₆₀ (1: 1) filter had a similar open circuit voltage (V _OC ) = 0.91 ± 0.01 V, but with a reduced polaron- The FF was increased to 62 ± 1% due to exciton quenching ^2′3 . However, J _SC = 12.8 ± 0.3 mA / cm ² , which is slightly smaller due to the above, and as shown in FIG. 23 (b), λ <420 nm and λ> 550 nm. Resulted in a reduced EQE. Overall, PCE increased slightly to 7.2 ± 0.2% under 1 sun irradiation.

OPV cells containing a buffer of BPhen: C ₆₀ / BPhen compound had an 18% improvement compared to control and had FF = 66 ± 1%. The _VOC also increased from 0.91 ± 0.1 V for control to 0.93 ± 0.1 V for cells containing BPhen: C ₆₀ / BPhen buffer. _{However, J CS} is decreased 5% compared to control, was reduced to 13.2 ± 0.4mA / cm ^2. Overall, the OPV cell containing the BPhen: C ₆₀ / BPhen buffer had a PCE = 8.1 ± 0.4% under pseudo-AM1.5G, 1 sun irradiation, a 14% increase compared to the control cell. Indicated.

In FIG. 24, for both cells, the absorption η _A of the organic photoactive region (ie, the mixed layer of DBP: C ₇₀ and the cap layer of pure C ₇₀ ) is calculated using the transfer matrix method ^4′5 , Further, the internal quantum efficiency (IQE) was calculated. Absorption of cells covered buffer, as described above ^3, _BPhen: by absorption of the mixed buffer _{C 60,} and decreased between lambda = 350 nm to 500 nm. At λ> 500 nm, the two cells had nearly identical absorption spectra because the mixing buffer was transparent.

Similarly, IQE increased between λ = 350 nm to 550 nm for cells containing BPhen: C ₆₀ / BPhen buffer compared to control cells. For example, the IQE for a cell containing a BPhen: C ₆₀ / BPhen buffer has 〜90% of the EQE between λ = 350 nm and 500 nm, reaching １００100% at λ = 430 nm, and all absorbed photons. Was converted to charge carriers collected by the electrodes.

Responsiveness (R) and PCE were examined as a function of light intensity ranging from 0.4 sun to 2.7 sun for BPhen: C ₆₀ / BPhen filtered cells and controls (FIG. 25). The responsiveness of the control cell monotonically decreases with intensity from R = 14.9 ± 0.4 A / Wat at 0.4 sun to 13.0 ± 0.4 A / W at 2.7 sun, while The filtered cell remained unchanged over this same range of solar intensity. The control cell also showed a PCE roll-off as the light intensity increased due to a monotonic decrease in responsiveness, as shown in FIG. The PCE of the cells containing the BPhen: C ₆₀ / BPhen buffer increased slightly in 1 sun to a maximum, with the decrease in FF being higher, probably caused by enhanced bimolecular recombination at high light intensity. Roll-off in light intensity started.

In the DBP: C ₇₀ PM-HJ cell including the BPhen: C ₆₀ / BPhen buffer, the thickness of the mixed buffer layer was also changed. FIG. 26 shows the JV characteristics and the EQE spectrum under the irradiation of 1 sun, and Table 8 summarizes the device performance.

As the thickness of the mixed buffer is increased, J _SC is decreased monotonically. As shown in FIG. 26 (b), as the mixed layer thickness increased, the EQE decreased over the visible spectrum. V _OC increased slightly from 0.91 ± 0.01 V for cells without a mixed buffer layer to 0.93 ± 0.01 V for cells with a 10 nm thick mixed buffer, and increased for thicker mixed buffer layers. Remained constant. The FF increases from 0.56 ± 0.01 for the control cell to 0.66 ± 0.01 for the 10 nm thick mixed buffer, and for the thicker mixed buffer, the increased series resistance as shown in Table 8 Due to roll off.

On the other hand, it includes a mixed layer which is modeled as a random distribution of molecules of C ₆₀ and BPhen, using 3D Monte Carlo simulations for the transport of re adjacent hopping in solid lattice, the charge transport through the mixed buffer layer Modeled. Ignoring columbium interactions between charges, we assumed that the lattice sites were of equal energy and excluded the energy difference due to the applied electric field. The relative hopping probability between sites was calculated using the Miller-Abrahams equation. During each time step of the model, the charge selected a random re-adjacency for hopping, weighted by the relative hopping probability. If the selected site contained a BPhen molecule, the charge instead remained immobile during that step. The movement of the charge in the mixed layer and the pure layer was otherwise identical.

  The average extraction time for different thicknesses was calculated by injecting charge into one side of the 100 × 100 pseudo-lattice under the electric field and measuring the time for charge to escape from the other side. FIG. 27 shows the average extraction time versus electric field as a function of mixed layer thickness. For the thickness of the mixed layer of interest, the electric field accelerated the transport of charge in the mixed layer, thus reducing the average extraction time as the electric field increased. As the thickness of the mixing buffer increased, the time for the charge to move through the mixed layer took longer. Therefore, the average extraction time was longer as the thickness of the mixed layer was increased.

To analyze the model predictions, the series resistance obtained by fitting the JV characteristics in the dark, as shown in Table 8, was obtained from the modeling from PM-HJ cells with different mixed layer thicknesses. And compared. The mobilities of the mixed layers having different thicknesses were calculated from the electric field dependence of the extraction time as 1 / electric field dependence of the extraction time, and all the simulated layers were 4.7 × 10 ⁻³ cm ² / V · An effective mobility of s was shown. This predicted that the resistance of the layer would depend linearly on the thickness, as shown in the inset of FIG. 1: predicted mobility of the mixed buffer layer 1, pure C ₆₀ than by one order of magnitude smaller, as the organic substance relatively high, these layers have been described or not efficiently extract how a charge of pure layers. As shown in the simulations above, these layers were effective in blocking excitons and resulted in spatial separation of excitons and polarons that suppressed quenching.

(Example 20)
The device shown in FIG. 28 was fabricated as shown. The overall structure is glass substrate / ITO (100 nm) / MoO ₃ (100 nm) / buffer 1 / DBP (20 nm) / C ₆₀ (40 nm) / buffer 2 / Ag (100 nm), buffer 1 and buffer 2, and The corresponding measured efficiency parameters are shown in Table 9. FIG. 28 (a) an active layer composed of DBP and _{C 60,} about the OPV cell containing a variety of buffers, 1 sun, under pseudo AM1.5G irradiation, shows the J-V about radiation, inset shows the NPD, FIG. 28 (b), regarding OPV cell comprising an active layer made of DBP and _{C 60,} and various buffers, shows the external quantum efficiency.

The thickness, composition and measured efficiency parameters for each filter are shown in Table 9. Compared to the reference, containing pure layer of NPD as filter, with a decrease of FF, it resulted in a significant increase in J _SC. Of DBP and NPD 1: Use of a filter consisting of a mixture of 1, as compared to the reference device, while still improving J _CS, compared to the use of NPD alone served to improve the FF. When used in conjunction with an electronic filter at the cathode, the NDP: DBP hole filter provided a 10% increase in PCE.

(Example 21)
The device shown in FIG. 30 was fabricated as shown. The overall structure was glass substrate / ITO / MoO ₃ (10 nm) / DBP: C ₇₀ (1: 8) (54 nm) / C ₇₀ (9 nm) / buffer / Al (100 nm). Devices were grown on commercially available pre-patterned ITO substrates. The substrate was cleaned using a solvent and a UV-ozone system. The organic layer, metal oxide and cathode were deposited in a thermal evaporator at a rate of 0.1 nm / sec. The device was encapsulated by placing an epoxy layer around the device and pressing the glass slide up. The epoxy was UV cured.

In one device, the buffer layer was a mixed layer of BPhen: C ₆₀ (1: 1) (10 nm) with a BPhen cap layer (5 nm). In another device, the buffer layer was a mixed layer of TPBI: C ₇₀ (1: 1) (10 nm) with a TPBi cap layer (3 nm). It should be noted that other wide energy gap materials may be used, such as those listed in Table 10 below and other materials described above.

To test the lifetime at elevated temperatures, devices were placed on a carrier board made from a printed circuit board. The contacts were soldered. A copper plate was attached to the device using a resistive heater to spread the heat across the device area. The temperature was measured using a thermocouple. The device was illuminated using a 1000 W / m ² xenon arc lamp and measured every 30 minutes using a current-voltage source meter controlled by the Matlab program.

  31A-C show normalized performance values at various temperatures for devices using BPhen, and FIGS. 32A-D show normalized performance values at various temperatures for devices using TPBi. Show. As shown by the respective Tg's shown in FIGS. 31A-C and 32A-D, BPhen has morphological instability compared to TPBi, so the performance of the device using BPhen uses TPBi. It degraded significantly faster over time than the performance of the device, especially as the temperature increased.

(Example 22)
The device shown in FIG. 33 was fabricated using the same method as described in Example 21 as shown. The overall structure is glass substrate / ITO / MoO ₃ (10 nm) / C ₇₀ : DBP (8: 1) (54 nm) / C ₇₀ (9 nm) / buffer (15 nm) / Al (100 nm), as shown in the figure. And various buffer layers, including a mixed layer of a wide energy gap material and an electron conducting material, and a cap layer of a wide energy gap material. It should be noted that other wide energy gap materials may be used, such as the materials described above. FIG. 33 shows a comparison at 55 ° C. of a device using BPhen for the buffer layer and three devices each using a different wide energy gap material with a higher Tg than BPhen (ie, BAlq, 3TPYMB and TPBi). 4 shows normalized power conversion efficiency.

As shown in FIG. 33, the degradation of device performance over time was significantly less for devices containing a mixed buffer layer containing a wide energy gap material with a higher Tg than BPhen. The molecular structure of these materials, with the molecular structures of other wide energy gap material (Alq ₃ and BP4mPy), shown in FIGS. 34 to 38.

FIGS. 39-41 show normalized responsiveness, fill factor, V _OC at 55 ° C. over time for devices containing mixing buffers each containing a mixture of C ₇₀ and TPBi, one of 3TPYMB and BAlq. And FIG. As shown, the normalized performance values (e.g., based on PCE, _VOC , FF and R) of the device containing one of TPBi, 3TPYMB and BAlq are the performance of the device containing BPhen (FIGS. 31A-C). And the performance of the BPhen device shown in FIG. 33) remained significantly higher over time.

(Example 23)
The device shown in FIG. 42 was fabricated using the same method as described in Example 21 as shown. The overall structure is glass substrate / ITO (160 nm) / MoO ₃ (10 nm) / C ₇₀ : DBP (8: 1) (54 nm) / C ₇₀ (9 nm) / 3TPYMB: C ₆₀ (1: 1) (10 nm) / Al (100 nm). _3TPYMN: 10nm layer of _{C 60} was buffer layer containing 3TPYMB (Tg ≒ 106 ℃ of 3TPYMB) a wide energy gap material. The lifetime of the device at the elevated temperature was tested using the same method as described in Example 21. FIGS. 43-46 show normalized responsiveness, fill factor, _VOC and PCE over time at 55 ° C., 70 ° C., 85 ° C., and 100 ° C. for the device of FIG. 42, respectively.

Claims (21)

Two electrodes in an overlapping relationship, including an anode and a cathode,
A photoactive region disposed between the two electrodes and comprising at least one donor material and at least one acceptor material forming a donor-acceptor heterojunction, wherein the at least one acceptor material has a minimum free orbital energy; Level (LUMO _Acc ) and the highest occupied orbital energy level (HOMO _Acc ));
An exciton blocking electronic filter disposed between the cathode and the at least one acceptor material, wherein the electronic filter is a mixture comprising at least one cathode side wide energy gap material and at least one electron conducting material ) And
At least one cap layer disposed between the exciton blocking electron filter and the cathode (where the at least one cap layer and the at least one cathode side wide energy gap material include the same material; )When,
Including
The wide energy gap material on the at least one cathode side comprises:
A lowest unoccupied orbital energy level (LUMO _CS-WG ) that is equal to or less than the LUMO _Acc ;
A highest occupied orbital energy level (HOMO _CS-WG ) which is _{equal to} or higher than the HOMO _Acc or smaller than 0.3 eV than the HOMO _Acc ;
An energy gap of HOMO _CS-WG- LUMO _CS-WG wider than an energy gap of HOMO _Acc- LUMO _Acc ;
A glass transition temperature of 85 ° C. or higher,
Has,
The at least one electron-conducting material, an organic photosensitive optoelectronic device having said at _{LUMO Acc} or more, or less lowest unoccupied molecular orbital energy level in the range of 0.2eV than the _{LUMO Acc (LUMO EC).}   The wide energy gap material on the at least one cathode side is 3,3 ′, 5,5′-tetra [(m-pyridyl) -phen-3-yl] biphenyl (BP4mPy), 2,2 ′, 2 ″- (1,3,5-benzintriyl) -tris (1-phenyl-1-H-benzimidazole) (TPBi), bis (2-methyl-8-quinolinolate) -4- (phenylphenolato) aluminum (BAlq) ), Tris (8-hydroxy-quinolinato) aluminum (Alq3), tris (2,4,6-trimethyl-3- (pyridin-3-yl) phenyl) borane (3TPYMB), 4,40- (1,3- Phenylene) bis (2,6-di-tolylpyridine-3,5-dicarbonitrile) (m-MPyCN), 4,40- (1,3-phenylene) bis (2 -Di (biphenyl-4-yl) pyridine-3,5-dicarbonitrile) (m-PhPyCN), 4,40- (1,3-phenylene) bis (2,6-diphenylpyridine-3,5-di (Carbonitrile) (m-PyCN), 6,60- (1,4-phenylene) bis (2-phenyl-4-p-tolylnicotinonitrile) (p-PPtNN), 4,40- (1,4- The device of claim 1, comprising a material selected from phenylene) bis (2-phenyl-6-p-tolynicotinonitrile) (p-PPtNT), and derivatives thereof.   The device of claim 1, wherein the wide energy gap material has a glass transition temperature between 85-200C.   The device of claim 1, wherein the wide energy gap material has a glass transition temperature between 100 and 165C. The device of claim 1, wherein the HOMO _CS-WG is greater than the HOMO _Acc and the LUMO _CS-WG is smaller than the LUMO _Acc . The device of claim 1, wherein the LUMO _EC is equal to the LUMO _Acc . The device of claim 1, wherein the LUMO _EC is greater than the LUMO _Acc . The device of claim 1, wherein the LUMO _CS-WG is smaller than the LUMO _EC .   The method of claim 1, wherein the at least one acceptor material comprises a material selected from subphthalocyanine, subnaphthalocyanine, dipyrine complex, BODIPY complex, perylene, naphthalene, fullerene, functionalized fullerene derivative, and derivatives thereof. device.   10. The device of claim 9, wherein the at least one acceptor material comprises a material selected from a fullerene and a functionalized fullerene derivative.   The at least one electron conducting material comprises a material selected from subphthalocyanine, subnaphthalocyanine, dipyrine complex, BODIPY complex, perylene, naphthalene, fullerene, functionalized fullerene derivative, and derivatives thereof. Devices.   The device of claim 1, wherein the at least one acceptor material and the at least one electron conducting material comprise the same material.   The device of claim 1, wherein the mixture comprises the at least one cathode-side wide energy gap material and the at least one electron conducting material in a volume ratio ranging from 10: 1 to 1:10.   The device of claim 1, wherein the mixture comprises the at least one cathode side wide energy gap material and the at least one electron conducting material in a volume ratio ranging from 2: 1 to 1: 2. The device of claim 1 1 comprising at least one electron-conducting material, a material selected from fullerenes and functionalized fullerene derivative. The at least one electron-conducting material, the device according to claim 15 comprising a material selected from C ₆₀ and C _70. The at least one acceptor material, The device of claim 16 comprising a material selected from C ₆₀ and C _70. 17. The device of claim 16 , wherein the at least one cathode side wide energy gap material comprises a material selected from BP4mPy, TPBi, BAlq, Alq3, and 3TPYMB. 18. The device of claim 17 , wherein the at least one cathode side wide energy gap material comprises TPBi. 20. The device of claim 19 , wherein said at least one donor material comprises tetraphenyldibenzoperiflanthene (DBP).   The device of claim 1, wherein the at least one cathode side wide energy gap material comprises TPBi.