UV-recovery transparent photovoltaic cell

Abstract

To provide transparent photovoltaic cells.SOLUTION: A transparent photovoltaic cell includes a first visibly transparent electrode, a visibly transparent active layer including a light absorbing material that has a bandgap greater than or equal to about 2.75 eV, and a second visibly transparent electrode. The active layer is disposed between the first transparent electrode and the second transparent electrode. The transparent photovoltaic cell is visibly transparent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 62 / 615,283, filed January 9, 2018, the entire disclosure of which is incorporated herein by reference.

[0002] [Government Rights] This invention was made with government support under Grant No. 1807573 from the National Science Foundation. The government has certain rights in this invention.

[0003] [Technical Field] The present disclosure relates to ultraviolet (UV) light harvesting transparent photovoltaic cells. [Background technology]

[0004] This section provides background information related to the present disclosure, but is not necessarily prior art.

[0005] Transparent photovoltaic (TPV) technology offers an effective approach to creating smart windows in buildings, vehicles, and greenhouses. TPVs can both regulate solar heat transfer and generate electricity by photovoltaic conversion of the invisible portion of the solar spectrum. The overall average visible transmittance (AVT) is often the most important parameter in determining whether a TPV is acceptable, due to the stringent aesthetic requirements imposed on TPV applications in portable electronics and windows. To achieve the best combination of transparency and efficiency, selective harvesting of all of the invisible portion of the solar spectrum (e.g., near-infrared and ultraviolet) is required, limiting efficiency to a maximum of 20.1%. Currently, efficiencies of around 5% have been achieved, with AVTs exceeding 50%.

[0006] Although the UV component of the total solar photon flux is substantially smaller, theoretical efficiencies of up to 7% are achievable. The approach of selectively harvesting UV-only photons allows for very high photovoltages (over 1.5 V). It also allows for integration with conventional semiconductors (e.g., GaN, ZnO, and NiO). To date, only a few UV-harvesting TPV devices have been reported. For example, a NiO / ZnO semitransparent UV photovoltaic cell with a power conversion efficiency (PCE) of 0.1% has been reported. However, this cell's efficiency is severely limited due to its large bandgap (3.3 eV). More recently, UV-harvesting organic TPVs with PCEs up to 1.5% and AVTs of 60% have also been demonstrated. However, the visible bandgap of these TPVs is approximately 2.4 eV. These early studies were promising and demonstrated the excellent potential of TPVs for applications. Ultimately, however, the bandgap, far from the ideal cutoff, limits the potential for further optimization.

[0007] This UV harvesting approach allows the use of semiconductors that absorb over a continuous wavelength range, which also offers significant untapped opportunities for halide perovskites, which are currently being explored as alternatives to Si, CdTe, and GaAs. Halide perovskite materials have emerged as strong candidates for light harvesting due to their excellent photovoltaic properties, high quantum efficiency, and guaranteed efficiencies up to 22.7%. Perovskite materials are also among the least expensive light-absorbing semiconductor materials, with bandgaps that can be easily tuned by controlling their composition. Therefore, TPV devices fabricated from perovskite materials are desirable. Summary of the Invention

[0008] This section provides an overview of the present disclosure. This section is not intended to be an exhaustive disclosure of the scope or full scope of the present disclosure.

[0009] In various embodiments, the present technology provides a transparent photovoltaic cell comprising: a visible transparent first electrode; a visible-transparent active layer including a light-absorbing material having a band gap of about 2.75 eV or greater; a visible transparent second electrode; A transparent photovoltaic cell comprising: the active layer is disposed between the first transparent electrode and the second transparent electrode; The transparent photovoltaic cell is visually transparent.

[0010] In one embodiment, the band gap of the light absorbing material is about 2.75 eV or more and about 3.2 eV or less.

[0011] In one embodiment, the light absorbing material absorbs ultraviolet light (UV light) having a wavelength of about 450 nm or less.

[0012] In one embodiment, the light-absorbing material does not substantially absorb light having a wavelength of about 450 nm or greater.

[0013] In one embodiment, the transparent photovoltaic cell reflects at least about 10% of light having a wavelength of at least about 650 nm and at most about 5000 nm.

[0014] In one embodiment, the light absorbing material is a halide perovskite.

[0015] In one embodiment, the halogenated perovskite comprises halogenated perovskite nanocrystals.

[0016] In one embodiment, the halogenated perovskite is represented by the formula ABX3: wherein A is methylammonium (MA), formamidinium (FA), ethanediammonium (EA), isopropylammonium, dimethylammonium, guanidinium, piperidinium, pyridinium, pyrrolidinium, imidazolium, t-butylammonium, Na, K, Rb, Cs, or a combination thereof; B is Pb, Sn, Ge, Cu, Sr, Ti, Mn, Bi, Zn or a combination thereof; X is a halogen or a combination of halogens.

[0017] In one embodiment, the halogenated perovskite contains F, Cl, Br, and I and has a band gap of about 2.75 eV or more and about 3.2 eV or less.

[0018] In one embodiment, the halogenated perovskite comprises Cl and one or more other halides.

[0019] In one embodiment, the light absorbing material is a metal halide, a metal nitride, a metal sulfide, a metal selenide, a metal telluride, an alloy thereof, or a combination thereof.

[0020] In one embodiment, the metal halide is PbI2, PbCl2, PbBr2, PbI X Br (1-X) , PbI X Cl (1-X) , PbBr X Cl (1-X) , Snl2, SnCl2, SnBr2, SnI X Br (1-X) , SnI X Cl (1-X) , SnBr X Cl (1-X) , GeI2, GeCl2, GeBr2, GeI X Br (1-X) , GeI X Cl (1-X) , GeBr X Cl (1-X), InI3, InCl3, InBr3, TiI3, TiCl3, TiBr3, GaI3, GaBr3, GaCl3, AlCl3, AlBr3, AlI3, A2TiI6, A2TiCl6 and A2TiBr6, where A is an alkali metal (Li, Na, K, Rb, Cs or a combination thereof), an organic cation (methylammonium (MA), formamidinium (FA), ethanediammonium (EA), isopropylammonium, dimethylammonium, guanidinium, piperidinium, pyridinium, pyrrolidinium, imidazolium, t-butylammonium or a combination thereof), or a combination thereof; and 0≦X≦1, The metal nitride is In (X) Ga (1-X) N and In (X) Al (1-X) N, where 0≦X≦1; The metal sulfide is ZnS (X) Se (1-X) wherein 0≦X≦1; The metal selenides include ZnSe and ZnO. (X) Se (1-X) and Zn (X) Mg (1-X) Se, where 0≦X≦1; The metal telluride is Zn (X) Mg (1-X) Te and BeSe (X) Te (1-X) (wherein 0≦X≦1).

[0021] In one embodiment, the transparent photovoltaic cell transmits visible light and has an average visible light transmittance of about 45% or greater.

[0022] In one embodiment, the transparent photovoltaic cell has a color rendering index of greater than about 80 based on the Air Mass 1.5 Global (AM1.5G) solar spectrum.

[0023] In one embodiment, the visibly transparent first electrode is a visibly transparent anode and the visibly transparent second electrode is a visibly transparent cathode.

[0024] In one embodiment, the transparent photovoltaic cell further comprises an accessory layer disposed between the visibly transparent first electrode and the visibly transparent active layer, the accessory layer being an electron transport layer, an electron extraction layer, a hole blocking layer, or a buffer layer.

[0025] In one embodiment, the accessory layer comprises poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), poly(3-hexylthiophene-2,5-diyl) (P3HT), N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine (NPD), N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine (TPD), 2,2',7,7'-tetrakis(N,N-diphenylamino)-2,7-diamino-9,9-spirobifluorene (spiro-TAD), poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD), or a combination thereof.

[0026] In one embodiment, the transparent photovoltaic cell further comprises an accessory layer disposed between the first visibly transparent active layer and the visibly transparent second electrode, the accessory layer being an electron transport layer or an electron extraction layer.

[0027] In one embodiment, the accessory layer comprises one or more of fullerenes, ZnO, TiO2, NiO, MoO3, conductive nanotubes, and conductive nanoparticles.

[0028] In one embodiment, the transparent photovoltaic cell further comprises an accessory layer disposed between the visibly transparent active layer and the visibly transparent second electrode, the accessory layer being an electron transport layer or an electron extraction layer that provides an ohmic contact between the visibly transparent active layer and the visibly transparent second electrode.

[0029] In one embodiment, the accessory layer comprises [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), Al-doped ZnO (AZO), TiO2, bathocuproine (BCP), MoO3, or a combination thereof.

[0030] In one embodiment, the visible transparent second electrode comprises a transparent conductive oxide, a nanowire mesh, a conductive oxide nanoparticle, a conductive nanotube, a thin metal layer, or a combination thereof.

[0031] In one embodiment, the visibly transparent second electrode comprises a thin metal layer containing silver (Ag) and a conductive layer containing aluminum tris(8-hydroxyquinolinate) (Alq3) or indium tin oxide (ITO); The thin metal layer is disposed between the visible transparent active layer and the conductive layer.

[0032] In one embodiment, the transparent photovoltaic cell further comprises a visibly transparent substrate disposed over the visibly transparent first electrode, the substrate comprising glass, a rigid polymer, or a flexible polymer.

[0033] In one embodiment, the transparent photovoltaic cell has a power conversion efficiency of about 0.3% or greater.

[0034] In one embodiment, the transparent photovoltaic cell has an external quantum efficiency of about 20% or greater at any wavelength less than about 450 nm.

[0035] In one embodiment, the transparent photovoltaic cell does not include an additional active layer with a bandgap less than 2.75 eV.

[0036] In one embodiment, the transparent photovoltaic cell does not include an additional active layer that has an external quantum efficiency greater than about 10% at wavelengths greater than about 450 nm.

[0037] In various embodiments, the present technology provides a transparent photovoltaic cell comprising: A substrate; A first electrode; an active layer including a light absorbing material that absorbs only ultraviolet light (UV light) having a wavelength less than about 450 nm, the light absorbing material being either (i) a halide perovskite or (ii) a metal halide, a metal nitride, a metal sulfide, a metal selenide, a metal telluride, an alloy thereof, or a combination thereof; A second electrode; A transparent photovoltaic cell comprising: the first electrode is located between the substrate and the active layer; the active layer is located between the first electrode and the second electrode; the substrate, the first electrode, the active layer, and the second electrode are all visible transparent; The transparent photovoltaic cell has an average visible light transmittance of about 50% or more.

[0038] In one embodiment, the transparent photovoltaic cell further comprises a visible transparent accessory layer located between the active layer and the second electrode, the accessory layer being an electron transport layer or an electron extraction layer comprising one or more of fullerenes, ZnO, TiO, NiO, MoO, conductive nanotubes, and conductive nanoparticles.

[0039] In one embodiment, the transparent photovoltaic cell comprises: a first optically transparent auxiliary layer located between the first electrode and the active layer; a visible transparent second auxiliary layer located between the active layer and the second electrode; It also has the first visible transparent accessory layer is an electron transport layer, an electron extraction layer, a hole blocking layer, or a buffer layer; The visibly transparent second accessory layer is an electron transport layer or an electron extraction layer.

[0040] In one embodiment, the transparent photovoltaic cell further comprises a visibly transparent third accessory layer located between the visibly transparent second accessory layer and the second electrode, the third accessory layer being an electron transport layer or an electron extraction layer that provides an ohmic contact between the visibly transparent second accessory layer and the second electrode.

[0041] In one embodiment, the second electrode is a first layer comprising a material selected from the group consisting of indium tin oxide (ITO), aluminum doped zinc oxide (AZO), fluorine doped tin oxide (FTO), indium zinc oxide, InZnAlO, zinc oxide, ZnAlO (ZAO), cadmium oxide, indium zirconium oxide (ZrIO), gallium zinc oxide (GZO), Al, Au, Ag, Mo, Cu, Ni, graphene, graphene oxide, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), metal nanowires, and combinations thereof; a second layer comprising aluminum tris(8-hydroxyquinolinate) (Alq3), 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP), N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPD), 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene, N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine (TPD), derivatives thereof, or combinations thereof; It also has The first layer is disposed between the active layer and the second layer.

[0042] In various embodiments, the present technology provides a transparent photovoltaic cell comprising: a visible transparent first electrode; a visible transparent second electrode; a visible-transparent active layer disposed between the visible-transparent first electrode and the visible-transparent second electrode, the active layer including a light-absorbing material that absorbs only light having a wavelength less than about 450 nm and does not substantially absorb light having a wavelength of about 450 nm or more; A transparent photovoltaic cell comprising: A transparent photovoltaic cell, wherein the light-absorbing material is either (i) or (ii) below: (i) a halogenated perovskite of the formula ABX3, wherein A is methylammonium (MA), formamidinium (FA), ethanediammonium (EA), isopropylammonium, dimethylammonium, guanidinium, piperidinium, pyridinium, pyrrolidinium, imidazolium, t-butylammonium, Na, K, Rb, Cs, or a combination thereof; B is Pb, Sn, Ge, Cu, Sr, Ti, Mn, Bi, Zn or a combination thereof; X is a halogen or a combination of halogens, a halogenated perovskite; (ii) PbI2, PbCl2, PbBr2, PbI X Br (1-X) , PbI X Cl (1-X) , PbBr X Cl (1-X) , Snl2, SnCl2, SnBr2, SnI X Br (1-X) , SnI X Cl (1-X) , SnBr X Cl (1-X) , GeI2, GeCl2, GeBr2, GeI X Br (1-X) , GeI X Cl (1-X) , GeBr X Cl (1-X)metal halides including one or more of InI3, InCl3, InBr3, TiI3, TiCl3, TiBr3, GaI3, GaBr3, GaCl3, AlCl3, AlBr3, AlI3, A2TiI6, A2TiCl6, and A2TiBr6 (wherein A is an alkali metal (Li, Na, K, Rb, Cs, or a combination thereof), an organic cation (methylammonium (MA), formamidinium (FA), ethanediammonium (EA), isopropylammonium, dimethylammonium, guanidinium, piperidinium, pyridinium, pyrrolidinium, imidazolium, t-butylammonium, or a combination thereof), or a combination thereof); In (X) Ga (1-X) N and In (X) Al (1-X) Metal nitrides containing one or more of N, ZnS (X) Se (1-X) metal sulfides, ZnSe, ZnO (X) Se (1-X) and Zn (X) Mg (1-X) metal selenides containing one or more of Se, Zn (X) Mg (1-X) Te and BeSe (X) Te (1-X) a metal telluride containing one or more of the following: These alloys, or Combinations thereof (wherein 0≦X≦1).

[0043] In one embodiment, the transparent photovoltaic cell is a rigid display, a flexible display, a watch crystal, an automotive glass, a smart window, a freestanding electrochromic window, or architectural glass.

[0044] Based on the disclosure herein, other areas of applicability of the present technology will be apparent. The description and specific examples in this section are for illustrative purposes only and are not intended to limit the scope of the present disclosure. [Brief explanation of the drawings]

[0045] [Figure 1] The accompanying drawings are intended only to illustrate selected embodiments (rather than all possible embodiments) and are not intended to limit the scope of the present disclosure. Figure 1 is a diagram of a first element according to various aspects of the present technology. [Figure 2] FIG. 2 is a diagram of a second element according to various aspects of the present technology. [Figure 3] FIG. 3 is a diagram of a third element in accordance with various aspects of the present technology. [Figure 4] FIG. 4 is a diagram of a fourth element in accordance with various aspects of the present technology. [Figure 5A] FIG. 5A shows the absorption (1-transmission) spectra of halide perovskite films of various compositions. [Figure 5B] FIG. 5B shows the structure of a perovskite ultraviolet light harvesting transparent photovoltaic device. [Figure 6A] Figure 6A shows the surface morphology of a UV-harvesting perovskite film (MAPbCl). The scale bar is 1 μm. [Figure 6B] Figure 6B shows the surface morphology of a UV-harvesting perovskite film (MAPbCl2.4Br0.6). The scale bar is 1 μm. [Figure 6C] FIG. 6C is a graph showing the XRD pattern of a UV-harvesting perovskite film. [Figure 6D] Figure 6D shows a photograph of the halide perovskite films: MAPbI3 is black, MAPbBr3 is deep orange, MAPbCl2.4Br0.6 is pale yellow, and MAPbCl3 is colorless. [Figure 7A] Figure 7A shows a scanning electron microscope (SEM) image of a cross section of a MAPbCl transparent photovoltaic (TPV) device. The scale bar is 200 nm. [Figure 7B] Figure 7B shows a cross-sectional SEM image of a MAPbCl2.4Br0.6TPV device. The scale bar is 200 nm. [Figure 8A]Figure 8A shows the current-voltage curve (J-V curve) of a UV-recovery transparent perovskite photovoltaic device, measured under conditions of 1 solar irradiance. [Figure 8B] Figure 8B shows a histogram of the PCE measured for 50 different MAPbCl3 devices (white) and 86 different MAPbCl2.4Br0.6 devices (black). [Figure 9A] Figure 9A shows the absorption (A), transmission (T), reflection (R), external quantum efficiency (EQE), and internal quantum efficiency (IQE) of MAPbCl3 UV-harvesting transparent perovskite photovoltaic devices. [Figure 9B] Figure 9B shows the absorption (A), transmission (T), reflection (R), external quantum efficiency (EQE), and internal quantum efficiency (IQE) of MAPbCl2.4Br0.6 UV-harvesting transparent perovskite photovoltaic devices. [Figure 9C] Figure 9C is a photograph of a MAPbCl3 UV-harvesting transparent perovskite device. [Figure 9D] Figure 9D is a photograph of a MAPbCl2.4Br0.6 UV-harvesting transparent perovskite device. [Figure 10] FIG. 10 is a plot of bandgap measurements based on absorption of halide perovskite films. [Figure 11] FIG. 11 is a plot of the band gap measurement based on the absorption of PbI2 films. [Figure 12A] Figure 12A shows the crystal structure of PbI2. [Figure 12B] FIG. 12B shows the structure of a lead halide solar cell. [Figure 12C] FIG. 12C is a graph showing the short-circuit current of opaque PbI2 solar cells fabricated from PbI2 precursor solutions of various concentrations. [Figure 12D] FIG. 12D is a graph showing the power conversion efficiency of opaque PbI 2 solar cells fabricated from PbI 2 precursor solutions of various concentrations. [Figure 13] FIG. 13 is a graph showing the thickness of PbI2 films as a function of PbI2 precursor solution concentration. [Figure 14A]Figure 14A is a scanning electron microscope (SEM) image of a PbI2 film prepared from a 0.1 M PbI2 precursor solution. The scale bar is 1 μm. [Figure 14B] Figure 14B shows an SEM image of a PbI2 film prepared from a 0.2 M PbI2 precursor solution. The scale bar is 1 μm. [Figure 14C] Figure 14C shows an SEM image of a PbI2 film prepared from a 0.5 M PbI2 precursor solution. The scale bar is 1 μm. [Figure 14D] Figure 14D shows an SEM image of a PbI2 film prepared from a 1 M PbI2 precursor solution. The scale bar is 1 μm. [Figure 15A] FIG. 15A is a graph showing the open circuit voltage of opaque PbI 2 solar cells fabricated from PbI 2 precursor solutions of various concentrations. [Figure 15B] FIG. 15B is a graph showing the fill factors of opaque PbI 2 solar cells fabricated from PbI 2 precursor solutions of various concentrations. [Figure 16A] FIG. 16A is a photograph of lead halide films doped with bromine or chlorine at various doping rates (lead concentration: 0.3 M). [Figure 16B] FIG. 16B is a graph showing the transmission spectra of lead halide films doped with bromine or chlorine at various doping rates (lead concentration: 0.3 M). [Figure 17A] FIG. 17A shows the X-ray diffraction patterns (XRD patterns) of Br-doped lead halide films with various doping rates. [Figure 17B] FIG. 17B shows the XRD patterns of Cl-doped lead halide films with different doping rates. [Figure 17C] FIG. 17C shows the XRD patterns of lead halide films doped with Br or Cl at a doping rate of 10% mol, or undoped lead halide films. [Figure 18A] FIG. 18A is a graph showing the short circuit current density (Jsc) of opaque lead halide solar cells fabricated from bromine or chlorine doped lead halide precursor solutions at various doping rates. [Figure 18B]FIG. 18B is a graph showing the open circuit voltage (Voc) of opaque lead halide solar cells fabricated from bromine or chlorine doped lead halide precursor solutions at various doping rates. [Figure 18C] FIG. 18C is a graph showing the fill factor (FF) of opaque lead halide solar cells fabricated from bromine or chlorine doped lead halide precursor solutions at various doping rates. [Figure 18D] FIG. 18D is a graph showing the power conversion efficiency (PCE) of opaque lead halide solar cells fabricated from bromine or chlorine doped lead halide precursor solutions at various doping rates. [Figure 19A] FIG. 19A is a photograph of a lead halide TPV. [Figure 19B] FIG. 19B shows the transmission spectra of PbI2 films prepared from PbI2 precursor solutions with different concentrations. [Figure 19C] FIG. 19C shows the transmission spectra of lead halide TPVs fabricated from PbI2 precursor solutions of various concentrations. [Figure 20A] FIG. 20A shows the transmission spectrum of a lead halide film prepared from a 0.2 M lead halide precursor solution (bromine or chlorine doped at a doping rate of 10%). [Figure 20B] FIG. 20B shows the transmission spectrum of a lead halide TPV fabricated from a 0.2 M lead halide precursor solution (bromine or chlorine doped at 10% doping). [Figure 21A] FIG. 21A is a photograph of a fully assembled PbI1.8Br0.2 TPV device (unpatterned). [Figure 21B] FIG. 21B shows the transmission (T), reflection (R) and external quantum efficiency (EQE) spectra of the PbI1.8Br0.2TPV device shown in FIG. 21A. [Figure 22A] FIG. 22A is a photograph of a PbI1.8Br0.2 film and a TPV device fabricated from a 0.2 M PbI1.8Br0.2 precursor solution. [Figure 22B]FIG. 22B shows the transmission spectra of the film and TPV device shown in FIG. 22A. [Figure 23A] FIG. 23A shows the short-circuit current density (Jsc) of PbI2TPV, PbI1.8Br0.2TPV, and PbI1.8Cl0.2TPV at concentrations of 0.1M, 0.2M, and 0.3M. [Figure 23B] FIG. 23B shows the open circuit voltage (Voc) of PbI2TPV, PbI1.8Br0.2TPV, and PbI1.8Cl0.2TPV at concentrations of 0.1M, 0.2M, and 0.3M. [Figure 23C] FIG. 23C shows the power conversion efficiency (PCE) of PbI2TPV, PbI1.8Br0.2TPV, and PbI1.8Cl0.2TPV at concentrations of 0.1M, 0.2M, and 0.3M. [Figure 23D] 23D is a graph showing initial device stability testing of PbI2TPV, PbI1.8Br0.2TPV, and PbI1.8Cl0.2TPV. Corresponding reference numerals indicate corresponding elements throughout the several views of the drawing. DETAILED DESCRIPTION OF THE INVENTION

[0046] Throughout this disclosure, exemplary embodiments are provided to fully convey the scope of the present disclosure to those skilled in the art. Numerous specific details, such as examples of specific compositions, components, elements, and methods, are described to provide a comprehensive understanding of the embodiments of the present disclosure. It will be apparent to those skilled in the art that the specific details need not be adopted, and the exemplary embodiments can be embodied in many different forms, none of which should be construed as limiting the scope of the present disclosure. In some exemplary embodiments, well-known manufacturing methods, well-known element structures, and well-known technologies are not described in detail.

[0047] The terms used herein are for the purpose of describing specific exemplary embodiments only and are not intended to be limiting. As used herein, the singular forms "a," "an," and "the" may be intended to encompass the plural, unless the context clearly dictates that only the singular is intended. The terms "comprising," "including," "including," "containing," and "having" are inclusive. Thus, while the terms specify the presence of stated features, elements, compositions, steps, integers, operations, and / or components, they do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The open-ended terms "comprising" and "including" should be understood as open-ended terms used to describe and claim each embodiment described herein. However, in certain aspects, the terms may be understood to contemplate more restrictive and limiting terms (such as "consisting of" or "consisting essentially of"). Thus, for any given embodiment that recites a composition, material, component, element, feature, integer, operation, and / or manufacturing step, the present disclosure also specifically includes embodiments that consist of (or consist essentially of) the recited composition, material, component, element, feature, integer, operation, and / or manufacturing step. In the case of "consisting of," alternative embodiments exclude any additional composition, material, component, element, feature, integer, operation, and / or manufacturing step. In the case of "consisting essentially of," any additional composition, material, component, element, feature, integer, operation, and / or manufacturing step that materially affects the basic and novel characteristics is excluded from the embodiment, but that does not materially affect the basic and novel characteristics may be included.

[0048] Unless a sequence is specifically specified, any method steps, manufacturing processes, and operations described herein should not be construed as requiring performance in the specific order described or illustrated, nor may additional or alternative steps be employed, unless otherwise indicated.

[0049] When a component, element, or layer is referred to as being "on," "engaged," "connected," or "coupled" with another element or layer, it may be directly on, engaged with, connected to, or coupled to the other component, element, or layer. Alternatively, intervening elements or layers may be present. Conversely, when an element is referred to as being "directly on," "directly engaged," "directly connected," or "directly coupled" with another element or layer, there may not be intervening elements or layers. Other terms used to describe relationships between elements should be interpreted similarly (e.g., "between" and "directly between," "adjacent" and "directly adjacent"). As used herein, the term "and / or" includes any and all combinations of one or more associated listed items.

[0050] In this specification, terms such as "first," "second," and "third" may be used to describe various steps, elements, parts, regions, layers, and / or portions. However, unless otherwise specified, these steps, elements, parts, regions, layers, and / or portions should not be limited by these terms. These terms are used only to distinguish one step, element, part, region, layer, or portion from another step, element, part, region, layer, or portion. As used in this specification, terms such as "first," "second," and other numerical terms do not imply an order or sequence unless clearly indicated by context. Therefore, a first step, first element, first part, first region, first layer, or first portion described below may be referred to as a second step, second element, second part, second region, second layer, or second portion without departing from the description of an exemplary embodiment.

[0051] For ease of description, spatially or temporally relative terms such as "in front," "after," "inside," "outside," "below," "below," "above," and "above" may be used herein to describe the relationship of one element or feature to another element or feature shown in the figures. Spatial or temporally relative terms may also be intended to encompass the use or operation of an element or system in different directions in addition to those depicted in the figures.

[0052] Throughout this disclosure, numerical values ​​represent approximate scales or range limits. Therefore, minor deviations from a given value are encompassed, and embodiments near the stated value and embodiments including the stated value are encompassed. Except for the examples set forth at the end of the detailed description, all numerical values ​​of parameters (e.g., parameters of quantities or conditions) in this specification (including the appended claims) should be understood to be modified in all instances by the term "about." This applies regardless of whether "about" actually precedes the numerical value. "About" means that the stated numerical value allows for some imprecision (some proximity to the exact value; roughly or reasonably close to a value; roughly close). Unless otherwise understood in the ordinary art, the imprecision introduced by "about" as used herein reflects the minimum deviation that can occur with conventional methods of measurement and use of the parameter. For example, "about" can include deviations of 5% or less. This variation is optionally 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, and in certain embodiments 0.1% or less.

[0053] Furthermore, the disclosure of a range includes disclosure of all values ​​and subranges within the entire range (including the endpoints and subranges of a given range). As noted above, ranges include endpoints unless otherwise specified. The disclosure of a range includes disclosure of all distinct values ​​within the entire range and subranges. Thus, for example, a range of "A to B" or "about A to about B" includes A and B.

[0054] Exemplary embodiments are more fully described with reference to the accompanying drawings.

[0055] The present technology provides transparent solar cell designs (e.g., transparent photovoltaic devices (TPVs)). As used herein, the term "transparent" encompasses an average linear beam visible light transmittance of about 45% or greater. As used herein, the term "semi-transparent" encompasses an average linear beam visible light transmittance of about 10% or greater and about 45% or less. Generally, the designs include a molecular active layer with strong absorption characteristics outside the visible light spectrum (e.g., the ultraviolet (UV) solar spectrum). The device may have a selective, highly reflective anti-reflective contact coating. The device may be formed as a heterojunction solar cell with a second light-absorbing layer having an absorption peak in the ultraviolet (UV) solar spectrum. The second light-absorbing material absorbs ultraviolet light while not substantially absorbing light at wavelengths above about 450 nm, above about 475 nm, or above about 500 nm (discussed below). The device may be formed into a tandem structure with one or more subcells coupled via a recombination zone. The device has a variety of applications. Example applications include rigid and flexible computer displays (used in desktop monitors, laptop or notebook computers, tablet computers, mobile phones, e-readers, etc.). Other example applications include watch crystals, automotive and architectural glass (sunroofs, smart windows, autonomous electrochromic windows, privacy glass, etc.). Photovoltaic devices may also be used for active power generation, for example, for completely self-powered home generation or for battery charging (or extending battery life).

[0056] As used herein, near-infrared (NIR) light is defined as light having a wavelength greater than about 650 nm and less than or equal to about 2000 nm. Ultraviolet (UV) light is defined as light having a wavelength greater than about 10 nm and less than about 450 nm. The use of a UV-absorbing active layer allows for the use of selectively highly reflective coatings, which optimize device performance while still allowing high transmission of visible light throughout the device. Visible light, as used herein, is defined as light to which the human eye responds significantly, and has a wavelength greater than or equal to about 450 nm and less than or equal to about 650 nm.

[0057] Halide perovskite materials are emerging as alternatives to silicon. They exhibit excellent photovoltaic properties, with efficiencies of up to 22.7% demonstrated, at extremely low cost. Semitransparent photovoltaic cells and spatially segmented transparent photovoltaic cells (TPVs) There has been growing interest in the application of halide perovskites to open up a broad range of development routes for these applications. However, these semiconductors have continuous absorption bands, which prevent them from selectively harvesting near-infrared wavelengths (near-infrared light, which is the target of conventional transparent photovoltaic cells (TPVs)) while ensuring high efficiency and transparency that meets the aesthetic requirements of many emerging applications. This technology provides the opportunity to develop TPVs based on perovskite semiconductors. Through a critical range of compositions, the bandgap of these semiconductors can be finely tuned to selectively harvest only ultraviolet (UV) photons within the bandgap range of 400–440 nm. This range is important; bandgaps below approximately 380 nm result in a much lower theoretical efficiency limit of less than 2.5%. Bandgaps above approximately 450 nm result in unacceptable levels of color or insufficient color rendering index (CRI). TPV devices have demonstrated power conversion efficiencies (PCEs) up to 0.52%, average visible transmittances (AVTs) up to 70.7%, and CRIs of over 92. This approach should theoretically provide efficiencies up to 7%, 100% visible transmittance, and CRIs above approximately 90. Practical optimization of these perovskite cells is currently limited by quantum efficiencies of 20-30%. This could readily provide TPVs with PCEs of 3-5% (comparable to the state-of-the-art near-infrared harvesting TPVs), and when combined with near-infrared harvesting TPVs, provides a pathway to even more efficient multijunction TPVs.

[0058] 1 shows an exemplary transparent photovoltaic cell 10 according to various embodiments of the present technology. The transparent photovoltaic cell 10 includes a first electrode 12, an active layer 14 including a light-absorbing material with a bandgap of about 2.75 eV or greater, and a second electrode 16. Each of the first electrode 12, the active layer 14, and the second electrode 16 is visible-transparent. The active layer 14 is disposed between the first electrode 12 and the second electrode 16.

[0059] As described below, in various embodiments, the transparent photovoltaic cell 10 may include two or more active layers 14. These active layers 14 have a bandgap of about 2.75 eV or greater or an external quantum efficiency of less than 10% at wavelengths greater than about 450 nm. In other words, the transparent photovoltaic cell 10 does not include any additional active layers with a bandgap less than 2.75 eV. Alternatively, the transparent photovoltaic cell 10 does not include any additional active layers with an external quantum efficiency of more than about 10% at wavelengths greater than about 450 nm.

[0060] In various embodiments, the band gap of the light-absorbing material is about 2.75 eV or more and about 3.2 eV or less. For example, in various embodiments, the band gap of the light-absorbing material is about 2.75 eV, about 2.8 eV, about 2.85 eV, about 2.9 eV, about 2.95 eV, about 3 eV, about 3.05 eV, about 3.1 eV, about 3.15 eV, or about 3.2 eV. Therefore, the wavelength of ultraviolet light absorbed by the light-absorbing material is about 470 nm or less, about 460 nm or less, about 450 nm or less, about 440 nm or less, about 430 nm or less, about 420 nm or less, about 410 nm or less, or about 400 nm or less.

[0061] The light-absorbing material absorbs ultraviolet light but does not substantially absorb light with wavelengths of about 450 nm or greater, about 460 nm or greater, or about 470 nm or greater. By "substantially no absorption," we mean that the light-absorbing material absorbs about 25% or less, about 20% or less, about 15% or less, about 10% or less, about 5% or less, or about 1% or less of light with wavelengths of about 450 nm or greater, about 460 nm or greater, or about 470 nm or greater. For example, in some embodiments, the light-absorbing material may have an absorption peak at wavelengths less than about 450 nm, but decreases in the visible range above about 450 nm. In such embodiments, it is understood that the light-absorbing material absorbs some visible light located at the edges. Additionally, a fully assembled transparent photovoltaic cell 10 has a maximum absorption peak in the active layer at wavelengths of about 450 nm or less.

[0062] The transparent photovoltaic cell 10 is transparent. Therefore, the transparent photovoltaic cell 10 transmits visible light and has an average visible light transmittance (AVT) of about 45% or more, about 50% or more, about 55% or more, about 60% or more, about 65% or more, about 70% or more, about 75% or more, about 80% or more, about 85% or more, or even about 90% or more. Furthermore, the transparent photovoltaic cell 10 has a CRI of about 80 or more, about 85 or more, about 90 or more, or about 95 or more, based on the Air Mass 1.5 Global (AM1.5G) solar spectrum. Thus, in various embodiments, the transparent photovoltaic cell 10 is visibly transparent. Therefore, when a human observer looks through the transparent photovoltaic cell 10, objects on the opposite side of the transparent photovoltaic cell 10 from the human observer appear substantially (or completely) natural color, substantially free (or completely) of coloration or haze.

[0063] Additionally, the transparent photovoltaic cell 10 conserves heat by reflecting NIR and IR light. More specifically, the transparent photovoltaic cell 10 has a maximum peak reflectance of about 10% or more, about 15% or more, about 20% or more, about 25% or more, about 35% or more, about 40% or more, or about 50% or more at wavelengths of about 650 nm or more and about 5000 nm or less. The light-absorbing material does not substantially or completely absorb light with wavelengths of about 650 nm or more and about 5000 nm or less. For example, other components of the transparent photovoltaic cell 10 (such as electrodes) may reflect and absorb a portion of the non-reflected light with wavelengths of about 650 nm or more and about 5000 nm or less that is not reflected. The remainder of the non-reflected light with wavelengths of about 650 nm or more and about 5000 nm or less is transmitted through the transparent photovoltaic cell 10. Thus, the transparent photovoltaic cell 10 can replace a low-e window or be combined with a low-e coating or a low-e window. In other embodiments, the transparent photovoltaic cell 10 is integrated into a multi-junction photovoltaic cell or device.

[0064] The power conversion efficiency (PCE) of the transparent photovoltaic cell 10 is about 0.3% or greater, about 0.5% or greater, about 1% or greater, about 1.5% or greater, about 3% or greater, about 5% or greater, about 6% or greater, or about 7% or greater.

[0065] The external quantum efficiency (EQE) of the transparent photovoltaic cell 10 at any wavelength less than about 450 nm is about 20% or greater, about 30% or greater, about 40% or greater, about 50% or greater, about 60% or greater, about 70% or greater, or about 80% or greater.

[0066] The light-absorbing material of the active layer 14 is either (i) a halide perovskite or (ii) a metal halide, metal nitride, metal sulfide, metal selenide, metal telluride, alloys thereof, or combinations thereof. The light-absorbing material is provided as a thin layer, nanoparticles, or nanocrystals.

[0067] In various embodiments, the light-absorbing material of active layer 14 is a halide perovskite. A perovskite is a material that has the same type of crystal structure as calcium titanate (CaTiO; i.e., a naturally occurring perovskite). This crystal structure is known as a "perovskite structure." That is, a perovskite structure with an oxygen-centered structure. XII A 2+VI B 4+ X 2- 3. The general formula for perovskite compounds is "ABX3." A and B are cations of different sizes (A cations are usually 1% larger than B cations). + The B cation is usually 2 +X is an anion bonded to both A and B. In an idealized cubic symmetry structure, the hexacoordinated B cation is surrounded by an octahedron of anions, and the A cation is octahedrally 12-coordinated. In various embodiments, the light-absorbing material comprises one or more of a perovskite, a mixed halide perovskite, an oxide perovskite, a layered halide perovskite, or one or more inorganic halide perovskites. The mixed halide perovskite is represented by the formula ABX3, where A is methylammonium (MA), formamidinium (FA), ethanediammonium (EA), isopropylammonium, dimethylammonium, guanidinium, piperidinium, pyridinium, pyrrolidinium, imidazolium, t-butylammonium, Na, K, Rb, Cs, or a combination thereof. B is Pb, Sn, Ge, Cu, Sr, Ti, Mn, Bi, Zn, or a combination thereof. X is a halogen or a combination of halogens. By mixing various A, B, and X components, a halide perovskite with a desired band gap can be obtained. For example, changing the halogen X from I to Br to Cl to F generally increases the band gap.

[0068] In some embodiments, the halide perovskite comprises F, Cl, Br, and I and has a bandgap of about 2.75 eV or more and about 3.2 eV or less.

[0069] In some embodiments, the halide perovskite comprises F and one or more other halides.

[0070] In some embodiments, the halide perovskite comprises Cl and one or more other halides.

[0071] In some embodiments, the halide perovskite comprises Br and one or more other halides.

[0072] In some embodiments, the halide perovskite comprises I and one or more other halides.

[0073] In various embodiments, the light-absorbing material of active layer 14 is a metal halide, a metal nitride, a metal sulfide, a metal selenide, a metal telluride, alloys thereof, and combinations thereof. Metal halides include PbI2, PbCl2, PbBr2, PbI X Br (1-X) , PbI X Cl (1-X) , PbBr X Cl (1-X) , Snl2, SnCl2, SnBr2, SnI X Br (1-X) , SnI X Cl (1-X) , SnBr X Cl (1-X) , GeI2, GeCl2, GeBr2, GeI X Br (1-X) , GeI X Cl (1-X) , GeBr X Cl (1-X) , InI3, InCl3, InBr3, TiI3, TiCl3, TiBr3, GaI3, GaBr3, GaCl3, AlCl3, AlBr3, AlI3, A2TiI6, A2TiCl6, and A2TiBr6, where A is an alkali metal (Li, Na, K, Rb, Cs, or a combination thereof), an organic cation (methylammonium (MA), formamidinium (FA), ethanediammonium (EA), isopropylammonium, dimethylammonium, guanidinium, piperidinium, pyridinium, pyrrolidinium, imidazolium, t-butylammonium, or a combination thereof), or a combination thereof. The metal nitride is In (X) Ga (1-X) N and In (X) Al (1-X) Metal sulfides contain one or more of the following: ZnS (X) Se (1-X) Metal selenides include ZnSe, ZnO (X) Se (1-X)and Zn (X) Mg (1-X) The metal tellurides contain one or more of Zn, Se, and (X) Mg (1-X) Te and BeSe (X) Te (1-X) In all of the above formulas, 0≦x≦1. In some embodiments, the light absorbing material comprises one or more of In (X) Ga (1-X) N(0.05≦x≦0.25), In (X) Al (1-X) N(0.25≦x≦0.7), ZnS (X) Se (1-X) (0.1≦x≦0.9), Zn (X) Mg (1-X) Se(0.05≦x≦0.5), Zn (X) Mg (1-X) Te (0.05≦x≦0.95) and BeSe (X) Te (1-X) (0.6≦x≦1). By selecting one or more appropriate values ​​of x and mixing various light-absorbing substances, the light-absorbing substance can be adjusted to have a desired band gap (about 2.75 eV or more and about 3.2 eV or less as described above). For example, by selecting x, it is possible to obtain a light-absorbing substance having a band gap of about 2.75 eV or more and about 3.2 eV or less. Alternatively, a plurality of light-absorbing substances (two or more light-absorbing substances) can be combined to achieve a band gap of about 2.75 eV or more and about 3.2 eV or less. Alternatively, the above may be combined.

[0074] The light-absorbing material is either (i) a halide perovskite or (ii) a metal halide, metal nitride, metal sulfide, metal selenide, metal telluride, alloy, or combination thereof, with the understanding that these materials are limited in that they must be incorporated into the transparent photovoltaic cell 10 and must meet each of the requirements discussed above (e.g., bandgap requirement, absorbance requirement, transmittance requirement, CRI requirement, PCE requirement, and EQE requirement).

[0075] The thickness T of the active layer 14AL is about 5 nm or more and about 5000 nm or less; about 10 nm or more and about 1000 nm or less; about 50 nm or more and about 600 nm or less; about 100 nm or more and about 500 nm or less; or about 200 nm or more and about 400 nm or less.

[0076] The first electrode 12 and the second electrode 16 are independently a visibly transparent anode and a visibly transparent cathode, respectively. The first electrode 12 and the second electrode 16 include a visibly transparent conductive material. The visibly transparent conductive material is independently selected from the group consisting of conductive oxides (such as indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), indium zinc oxide, InZnAlO (IZA0; e.g., 90 wt% In2O3, 5 wt% ZnO, and 5 wt% Al2O3), InAlZnSnO (IZA0), zinc oxide, ZnAlO (ZA0), cadmium oxide, indium zirconium oxide (ZrIO), and gallium zinc oxide (GZO)), metals (such as Al, Au, Ag, Mo, Cu, or Ni), carbon, graphene, graphene oxide, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), and combinations thereof. The visibly transparent conductive material can be a thin film, an ultrathin film, a nanowire (e.g., Al, Au, Ag, Mo, Cu, and / or Ni nanowires), a nanowire mesh, a nanotube (e.g., carbon nanotube), a nanoparticle, or a combination thereof.

[0077] In some embodiments, one or more of the first electrode 12 and the second electrode 16 comprises a first layer including a visible-transparent conductive material and a second layer including a transparent conductive organic material. In FIG. 1, the second electrode 16 includes an optional second electrode layer 18, which includes a transparent conductive organic material. The transparent conductive organic material fills the gaps in the visible-transparent conductive material (e.g., the electron transport layer) and reduces reflection. By reducing reflection, the transparent photovoltaic cell 10 becomes more transparent. Non-limiting examples of suitable conductive organic materials include aluminum tris(8-hydroxyquinolinate) (Alq), 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP), N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPD), 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene, N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine (TPD), derivatives thereof, and combinations thereof. In some embodiments, the second electrode layer 18 includes an inorganic compound (e.g., MoO, WO, or combinations thereof). The optional thickness T of the second electrode layer 18 is OM is about 5 nm or more and about 200 nm or less.

[0078] The thickness of the first electrode 12 is T E1 and the thickness of the second electrode 16 is T E2 The thickness T E1 and T E2 are each independently about 1 nm or more and about 200 nm or less; about 50 nm or more and about 150 nm or less; or about 75 nm or more and about 125 nm or less.

[0079] In some embodiments, one of the first electrode 12 or the second electrode 16 is disposed on a substrate. For example, FIG. 2 shows a second transparent photovoltaic cell 10′. The second transparent photovoltaic cell 10′ includes the same first electrode 12, active layer 14, second electrode 16, and optional second electrode layer 18 as the transparent photovoltaic cell 10 of FIG. 1. However, the first electrode 12 of the second transparent photovoltaic cell 10′ is disposed on a substrate 20. The substrate 20 is visibly transparent and includes glass, low-iron glass, plastic, poly(methyl methacrylate) (PMMA), poly-(ethyl methacrylate) (PEMA), (poly)-butyl methacrylate-co-methyl methacrylate (PBMMA), polyethylene terephthalate (PET), polycarbonate, or polyimide (e.g., Kapton® polyimide film (DuPont, Wilmington, DE)). The thickness T of the substrate 20 is 1 / 2 μm. S is about 1 μm or more and about 300 mm or less.

[0080] FIG. 3 illustrates a third transparent photovoltaic cell 10″. The third transparent photovoltaic cell 10″ includes the same first electrode 12, active layer 14, second electrode 16, and optional second electrode layer 18 as the transparent photovoltaic cell 10 of FIG. 1. The third transparent photovoltaic cell 10″ optionally includes the substrate 20 described with reference to FIG. 2. However, the third transparent photovoltaic cell 10″ includes one or more optional accessory layers. For example, in FIG. 3, the third transparent photovoltaic cell 10″ is shown with (i) an optional first accessory layer 22 disposed between the first electrode 12 and the active layer 14, (ii) an optional second accessory layer 24 disposed between the active layer 14 and the second electrode 16, and (iii) an optional third accessory layer 26 disposed between the optional second adjustment layer 24 and the second electrode 16. The accessory layers 22, 24, 26 may each independently be a hole transport layer, an electron blocking layer, a buffer layer, an electron transport layer, a hole blocking layer, or an electron extraction layer.

[0081] In various embodiments, the third transparent photovoltaic cell 10'' includes an optional first accessory layer 22. The first accessory layer 22 is a hole transport layer / operation function modifying layer / buffer layer / hole selective layer. The operation function modifying layer is added to obtain moisture. The optional first attachment layer 22 comprises poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), poly(3-hexylthiophene-2,5-diyl) (P3HT), N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine (NPD), N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine (TPD), 2,2',7,7'-tetrakis(N,N-diphenylamino)-2,7-diamino-9,9-spirobifluorene (spiro-TAD), poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD), CuSCN, CuI, MoO, NiO, or combinations thereof.

[0082] In various embodiments, the third transparent photovoltaic cell 10'' includes an optional second accessory layer 24. The second accessory layer 24 is an electron transport / extraction layer. The optional second accessory layer 24 is a fullerene (C 60 , C 70 , C 84 or phenyl-C 61 These include fullerenes, such as tetrabutyl methyl ester (PCBM), ZnO, TiO2, NiO, MoO3, nanotubes, conductive nanoparticles (such as ITO), or combinations thereof. For example, the role of fullerenes in perovskite solar cells is typically to facilitate electron extraction. Therefore, to prevent tail state absorption, the layers should be as thin as possible. The layer thickness is about 40 nm or less, about 20 nm or less, about 10 nm or less, about 5 nm or less, or about 1 nm or less.

[0083] In various embodiments, the third transparent photovoltaic cell 10″ includes an optional third accessory layer 26. The third accessory layer 26 is an electron transport layer / electron extraction layer / buffer layer / hole blocking layer. The optional third accessory layer 26 provides an ohmic contact between the active layer 14 and the second electrode 16. The optional third accessory layer 26 includes [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), Al-doped ZnO (AZO), TiO2, bathocuproine (BCP), MoO3, or a combination thereof.

[0084] The optional first accessory layer 22 has a thickness of T AL1 and the thickness of the optional second accessory layer 24 is T AL2 and the optional third auxiliary layer 26 has a thickness of T AL3 T AL1 , T AL2 and T AL3 and are each independently about 0.05 nm or more and about 100 nm or less. When the optional second attachment layer 24 includes fullerenes, the thickness T AL2 is approximately 50 nm or less.

[0085] When the third transparent photovoltaic cell 10'' includes an accessory layer 22, 24, 26 that is an electron transport layer or a hole transport layer, the electrode 12, 16 located adjacent to the electron transport layer is the cathode, and the electrode 12, 16 adjacent to the hole transport layer is the anode.

[0086] FIG. 4 illustrates a fourth transparent photovoltaic cell 10'''. The fourth transparent photovoltaic cell 10''' includes all of the layers described in connection with FIGS. 1-3. Specifically, the fourth transparent photovoltaic cell 10''' includes, in order, a substrate 20, a first electrode 12, a first accessory layer 22, an active layer 14, a second accessory layer 24, a third accessory layer 26, a second electrode 16, and a second electrode layer 18. The first accessory layer 22 is a hole transport layer, and the second accessory layer 24 is an electron transport layer. Thus, the first electrode 12 is an anode, and the second electrode 16 is a cathode. It is understood that each of the layers 12, 14, 16, 18, 20, 22, 24, and 26 is visibly transparent. It is also understood that any of the transparent photovoltaic cells 10, 10', 10'', and 10''' described herein may further include additional active layers and additional accessory layers.

[0087] Any of the transparent photovoltaic cells described herein can be used as rigid displays, flexible displays, watch crystals, automotive glass, or architectural glass, by way of non-limiting examples.

[0088] The present technology also provides a method for fabricating a transparent photovoltaic cell. As described above, this method includes adjusting a light-absorbing material to have an acceptable bandgap. When the light-absorbing material is a halide perovskite, the adjustment is performed by mixing various A, B, and X components. When the light-absorbing material is a metal halide, metal nitride, metal sulfide, metal selenide, metal telluride, alloys thereof, or combinations thereof, the adjustment is performed by alloying or mixing various metal halides, metal nitrides, metal sulfides, metal selenides, metal tellurides, or alloys thereof to adjust the bandgap to about 2.75 eV or more and about 3.2 eV or less.

[0089] The method includes sequentially disposing, on a visible transparent substrate, a layer including a first electrode, a layer including a light-absorbing material, and a layer including a second electrode. In various embodiments, the method also includes disposing an accessory layer over the transparent photovoltaic cell.

[0090] The deposition of the various layers can be carried out by any means known in the art. Non-limiting examples of means for depositing the various layers include spin coating, dip coating, doctor blading, chemical vapor deposition (CVD), drop casting, spray coating, plasma sputtering, vacuum deposition, and combinations thereof. Furthermore, layers containing perovskite materials can be deposited by a single-step synthesis without additives or a two- or more-step synthesis without additives. In a one-step synthesis, all perovskite reactants (e.g., PbI2 and MAI) are deposited from a single solution. In a two- or more-step synthesis, a deposition step of one reactant is followed by a reaction step of a second reactant (e.g., as a second deposition layer or a vapor-phase diffusion step).

[0091] As described above for the device, the accessory layer (which may be, for example, a hole transport layer or an electron transport layer) may be a single layer or multiple layers that are deposited separately and sequentially.

[0092] When all layers have been deposited, the method includes annealing the device. The annealing temperature is from about 75°C to about 150°C (e.g., about 90°C). The annealing time is from about 2 minutes to about 60 minutes or longer. In some embodiments, the annealing time is about 10 minutes. [Example]

[0093] Embodiments of the present technology are further illustrated by the following non-limiting examples.

[0094] Example 1 We leverage the tunability of halide perovskites as a platform to fabricate UV-harvesting TPVs with near-ideal bandgaps and visible-light absorption cutoffs, enabling high AVT and CRI. TPV devices fabricated from halide perovskites of various compositions have demonstrated AVTs of 70% and CRIs of over 92, along with PCEs of up to 0.52%. Assuming the quantum efficiency limit of these cells is 20-30%, current halide perovskite cells can easily achieve quantum efficiencies of over 90%, implying efficiencies of over 3%. We demonstrate novel halide perovskite compositions for highly transparent photovoltaic cell and TPV multijunction applications.

[0095] [method] Preparation of materials and precursors: Dimethylformamide (DMF, 99.8%, Aldrich.), dimethyl sulfoxide (DMSO, 99.9%, Aldrich.), PEDOT:PSS (Clevios PVP AI 4083, Heraeus; diluted to 10% with water before use), CH3NH3Cl (MACl, 98%, Aldrich.), PbBr2 (99%, Aldrich.), PbCl2 (98%, Aldrich.), C 60 Use HCl (99.9%, MER), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, 99%, Lumtech.), and tris-(8-hydroxyquinolinato)aluminum (Alq3, 99.5%, Lumtech.) as purchased. Prepare a mixed halide perovskite precursor solution by adding MACl:PbBr2:PbCl2 (135 mg, 220 mg, 389 mg) to a mixed solvent of DMF and DMSO (1.5 mL, 0.5 mL). Prepare a pure perovskite chloride precursor solution by adding MACl:PbCl2 (67.5 mg, 278 mg) to a mixed solvent of DMF and DMSO (1.5 mL, 0.5 mL). Stir the solution for 30 min and filter it through a 0.45 µm PTFE filter before use.

[0096] Device fabrication: A PEDOT solution was spin-coated onto a pre-cleaned ITO substrate at 6000 rpm for 10 seconds, followed by annealing at 100 °C for 5 minutes. A perovskite precursor was spin-coated onto the PEDOT film at 5000 rpm for 12 seconds, then transferred to a homemade vacuum chamber, depressurized to approximately 10 mTorr, and allowed to stand for 1 minute. The sample was then treated with methylamine gas for 2 seconds. The substrate was then transferred to a deposition chamber, where C was deposited as an electron extraction layer. 60 A 20 nm thick layer of silver and a 7.5 nm thick layer of BCP were then deposited to provide an ohmic contact. Finally, a 5 nm thick layer of silver and a 60 nm thick layer of Alq3 were deposited by thermal evaporation as transparent electrodes. The final measured device area was 4.85 mm². 2 Pass it through a shadow mask.

[0097] Measurements and Characterization: UV-VIS-NIR transmission and reflection spectra were measured using a PerkinElmer Lambda 800 spectrometer. XRD data were measured using a Bruker D2 phaser with CuKα radiation (0.154 nm). SEM images were taken using a field emission scanning electron microscope (Carl Zeiss Auriga Dual Column FIB SEM). Current density-voltage characteristics (JV curves) were obtained using a Keithley 2420 sourcemeter in darkness and under AM1.5G solar simulation. Light intensity was measured using an NREL-calibrated Si reference cell with a KG5 filter (xenon arc lamp, spectral mismatch factor: 1.20). 50 mVs -1The device is swept with a . The spectral mismatch in the TPV, which collects only the UV, is much more sensitive than measurements in the lamp spectrum. This is due to the large difference in quantum efficiency of the test cell relative to a calibrated Si reference cell. EQE measurements are performed using a QTH lamp equipped with a monochromator, chopper, lock-in amplifier, and a calibrated Si detector to measure intensity. JV and EQE are measured on unencapsulated devices / samples in open air. IQE is evaluated from device absorption measurements (A=1-RT) by measuring the reflectance of the entire device.

[0098] [result] Methylammonium lead halide (MAPbI3) is a perovskite semiconductor. While other compositions are being actively developed, little research has been done to optimize devices with bandgaps near the visible wavelength range. Figure 5A shows the absorption spectra of MA-based perovskite films substituted with various halides (Cl, Br, and I). Among these perovskites, perovskite iodide (MAPbI3) and perovskite bromide (MAPbBr3) exhibited significant visible light absorption. Therefore, these perovskites have been used as light absorbers in conventional opaque solar cells. While considerable efforts have been made to fabricate semitransparent solar cells, the AVT and CRI of devices generally remain low due to a direct trade-off between efficiency and transparency. To date, the reported AVT for perovskite-based TPVs is only 46% at best (for comparison, the AVT for organic TPVs is 66% at best). In comparison, MAPbCl3 has an absorption cutoff of 410 nm and an AVT of over 90%. Previous theoretical studies have shown that the bandgap of an ideal UV-only TPV is 430-440 nm. To broaden the absorption range while avoiding impact on visible light transmission, a doped composition, MAPbCl3, has been developed. 3-x Br xWe developed a device with an absorption cutoff sharply positioned between 410 and 440 nm. At a bromide substitution rate of 20%, the absorption of the mixed halide perovskite film extended to the ideal wavelength of 435 nm. Therefore, for the development of UV-recovery TPVs, we considered the use of perovskite films with compositions of MAPbCl3 or MAPbCl. 2.4 Br 0.6 The device was developed using a perovskite absorber material and a reverse device structure (Figure 5).

[0099] UV-harvesting perovskite films were fabricated by solution deposition via spin coating. Due to the limited solubility of the bulk Cl precursor in typical solvents, great care must be taken in the processing to form smooth perovskite layers with low haze and roughness to prevent short circuits. A vacuum-assisted solution deposition process combined with post-treatment with methylamine gas resulted in high-quality films with high transparency and low light scattering. MAPbCl3 films and MAPbCl3 films were fabricated using MAPbCl3. 2.4 Br 0.6 Scanning electron microscope (SEM) images of the films are shown in Figures 6A-B and 7A-7B. Both the pure perovskite chloride film and the bromine-doped perovskite film are smooth and uniform. Although these films lack the crystalline grains seen in the perovskite iodide film, strong diffraction peaks are observed in the X-ray diffraction (XRD) patterns. This indicates that the perovskite films are well crystallized and have a single preferred orientation. In Figure 6C, the diffraction peaks at 15.6°, 31.5°, and 48.0° correspond to the (100), (200), and (300) angles of the cubic crystal of MAPbCl3. With 20% bromine doping, the diffraction peaks shifted slightly to smaller angles (15.4°, 31.1°, and 47.4°). Nevertheless, the crystal structure was still cubic, consistent with other literature reports. This shift indicates a larger lattice parameter (a = 5.737 ± 0.008 Å) due to the larger Br atoms compared to pure MAPbCl3 (a = 5.677 ± 0.002 Å).

[0100] Photographs of various halide perovskite films are shown in Figure 6D. 2.4 Br0.6 Mixed halide perovskite films appear pale yellow due to their absorption cutoff at the edge of the visible spectrum (CRI > 95 corresponds to the highest theoretical TPV with visible light transmittance > 99.5% in the visible range, 435-670 nm). On the other hand, MAPbCl3 appears colorless, MAPbBr3 orange, and MAPbI3 dark brown.

[0101] A UV-harvesting TPV is fabricated with the structure shown in Figure 5B. A thin PEDOT layer (approximately 5 nm) is spin-coated on an ITO substrate to act as a hole extraction layer. After growing a perovskite film on the PEDOT layer, C 60 A film (20 nm) is deposited as an electron extraction layer. Next, bathocuproine (BCP) is deposited on top of the fullerene. Next, a top transparent electrode consisting of Ag (5 nm) / Alq3 (60 nm) is deposited. Figure 8A shows the current-voltage (JV) curves of the TPV devices, and Figure 8B shows the histograms of the PCEs of the devices. For the best pure perovskite chloride TPV device, the PCE was 0.33%, J SC is 0.67mAcm -2 , V OC The PCE was 1.18 V and the fill factor (FF) was 41.1%. On the other hand, the best mixed perovskite chloride TPV had a PCE of 0.52% and a J SC is 0.92mAcm -2 , V OC The voltage was 1.26V and the FF was 44.9%. 2.4 Br 0.6 has a wider absorption range than MAPbCl3, so MAPbCl 2.4 Br 0.6 Motoko's J SC is expected to be higher than that of the MAPbCl3 element. OC and FF also showed MAPbCl 2.4 Br 0.6 It can be inferred that the more difficult it is to fabricate pinhole-free MAPbCl3 films, the more charge recombination occurs, resulting in lower photovoltaic parameters for the MAPbCl3 devices (see Figures 6A-6B). 2.4Br 0.6 The average PCE for the devices was 0.24±0.04% and 0.42±0.06%, respectively (Table 1). The low deviation in PCE values ​​indicates the high reproducibility of these TPV devices.

[0102] [Consideration] Next, we systematically examine the optical properties of the UV-recovery TPV devices. Figures 9A and 9B show the absorption (A), reflection (R), transmission (T), external quantum efficiency (EQE), and internal quantum efficiency (IQE) spectra of each device. To confirm the consistency of the photon balance, we show that EQE + R + T < 100% at any position in the spectrum. MAPbCl3 perovskite film and MAPbCl 2.4 Br 0.6 Similar to the perovskite films, the corresponding TPV devices have a sharp absorption cutoff in the UV region while efficiently transmitting visible light. Both UV-recovery TPV devices have very high AVTs: 70.7% for MAPbCl3 and 70.7% for MAPbCl. 2.4 Br 0.6 The luminance was 69.7% (Table 1). Figures 9C-9D show photographs of the complete perovskite TPV devices. The film itself is very light yellow, but the addition of the top transparent cathode creates optical interference, resulting in a natural color. Above 650 nm, there is a decrease in the transmission curve and an increase in the reflection curve. However, because the active layer has very little absorption anywhere in the visible light spectrum, both devices exhibited luminances of 92.4 for MAPbCl3 and 92.4 for MAPbCl4 relative to the AM1.5G solar spectrum. 2.4 Br 0.6 exhibits a very high CRI of 93.1 (Table 1). CRI is another important factor in describing transparent elements. CRI quantitatively describes color quality in terms of the reproduction of an incident light source through a transparent medium and is also used in the lighting industry. A high CRI value indicates that the element has high aesthetic quality and will have little effect on color perception when installed in a window or display.

[0103] [Table 1]

[0104] Although we have demonstrated UV-harvesting TPV devices using halide perovskite semiconductors with nearly ideal optical properties (absorption cutoff, color rendition, and transparency), these devices may still be limited by their modest quantum efficiency. Without being bound by theory, this is likely due to the low solubility of perovskite chloride materials (limited to 30 wt % in DMF and DMSO). As a result, perovskite thin films (100–150 nm) can only harvest 60–70% of UV radiation (Figures 7A and 7B). This indicates an internal quantum efficiency (IQE) of less than 40%. Further improvements in film quality or crystal grain size (although currently exhibiting very favorable crystal orientation) would likely improve IQE. Furthermore, we observed that the device reflectance exceeds 10% in the 600–700 nm wavelength region, unnecessarily reducing transparency (Figures 9A and 9B). Overall, if we refine the manufacturing process, quantum efficiency will increase from 20% to 90%, FF from 45% to 70%, and V OC would increase from 1.26 V to 2.00 V. This mixed perovskite composition achieves an efficiency of over 5%, which is within sight of the theoretical efficiency limit of 7% near the transparency of glass alone (Table 2).

[0105] [Table 2]

[0106] We demonstrate UV-harvesting TPV devices based on a halide perovskite light-absorbing material platform. This suggests TPV devices with an ideal absorption cutoff for selective UV harvesting and minimal visual impact. It also provides a path to maximize performance. Based on the mixed-halide perovskite composition, TPV devices tuned to the ideal bandgap exhibit PCEs up to 0.52%, AVTs of 70%, and CRIs above 92. With an AVT as high as 70.7%, these UV-harvesting TPVs are among the photovoltaic cells with the highest AVTs reported to date. This demonstrates that the great potential of perovskite materials can be effectively translated into TPV devices. This type of technology is highly complementary to other near-infrared-harvesting TPVs in rapidly reaching both single-junction and multi-junction efficiency limits.

[0107] Example 2 TPV devices have many inherent advantages over opaque photovoltaics. However, achieving a balance between efficiency and transparency has been challenging. Few TPV devices have demonstrated PCEs greater than 1% when AVTs are greater than 70%. In this paper, we report a series of metal halide-based TPVs with improved efficiency and transparency. We systematically investigate the effects of the thickness and composition of the metal halide layer, and then evaluate the efficiency, transparency, and stability of metal halide TPVs. The results demonstrate that metal halide TPVs selectively absorb UV wavelengths, achieving efficiencies greater than 1% and AVTs greater than 70%. This provides a straightforward approach to fabricating UV-harvesting TPVs with high efficiency and transparency. These TPVs can be used as single-junction cells (or as components of multi-junction transparent and multi-junction opaque cells).

[0108] [background] Wavelength-selective TPVs focus on transmitting a large portion of visible light (VIS) while converting invisible light into electricity. This capability offers great potential for development in unconventional applications. TPVs have two key parameters: power conversion efficiency (PCE) and average visible transmittance (AVT). AVT is equally important as PCE, as it often defines the minimum threshold for adopting TPVs in novel applications. Furthermore, color rendering index (CRI) is an important parameter for TPV applicability. Although the PCE of TPVs has been significantly improved to over 5% (AVT of approximately 50%), much research has focused on semitransparent PVs. However, many emerging applications are only possible with a high AVT of approximately 70%.

[0109] Reducing visible light absorption is key to improving the AVT and CRI of TPVs. A few reports have explored the selective use of ultraviolet (UV) or near-infrared (NIR) absorbing materials to create highly transparent devices. Other studies have reported (i) UV-harvesting organic TPVs that achieved an AVT of 60% and a PCE of 1.5%, (ii) a series of organic salts with NIR harvesting properties and efficiencies up to 0.9% and an AVT of 60.4%, and (iii) organic-based NIR-harvesting TPVs with PCEs ranging from 0.9% to 2.2% and AVT values ​​(450–670 nm) ranging from 62% to 66%. Previous work has developed UV-wavelength-selective photovoltaic devices with an AVT of up to 73%, utilizing a sharp wavelength cutoff near the UV-visible cutoff, enabled by tuning the band gap of perovskite. However, previous research into the development of highly transparent TPVs has shown that it is difficult to improve TPV efficiencies above 1% while achieving AVT above 70%, even though the theoretical limit for UV-recovery TPVs is above 7% and for UV / NIR-recovery TPVs is above 21%.

[0110] Several types of metal halide semiconductors exist, including bulk semiconductors and metal halide nanoclusters. The latter have been incorporated as phosphorescent materials in luminescent solar concentrators (LSCs) and light-emitting diodes (LEDs). The former emerged as a by-product of metal halide perovskite solar cell research. Several metal halide semiconductors have been used as light-absorbing materials in opaque solar cells, demonstrating the potential of metal halide materials for photovoltaic applications. For example, InI-based solar cells (band gap: 2.0 eV) have been reported. Although the device efficiency was only 0.4%, this demonstrates the viability of InI as a photovoltaic material. Bismuth iodide (band gap: 1.72 eV) has also been used in solar cells as a light-harvesting material, demonstrating photovoltaic device efficiencies of up to 1.2%. However, because their band gaps are in the visible light range, these two metal halide materials are not suitable as wavelength-selective light-absorbing materials in TPVs. Studies of lead halide perovskite solar cells have shown that PbI2 (a perovskite precursor) can function as a photovoltaic material. The bandgap of PbI2 (2.4 eV) makes it unsuitable for single-junction opaque cells (Figure 11). However, increasing the bandgap to approach 2.7-2.8 eV may enable selective UV harvesting for TPVs. In reported demonstrations, TPVs using PbI2 as the light absorber have achieved efficiencies up to 0.75% with corresponding AVTs of 49%, but with low CRIs of 77. Therefore, TPV devices with improved efficiency and transparency are desirable.

[0111] In this paper, we demonstrate metal halide-based TPVs with efficiencies exceeding 1%. First, we optimized the thickness and processing of the PbI2 active layer. We also demonstrated that the bandgap can be tuned by systematically exploring chlorine and bromine doping. This approach has been demonstrated to work successfully with bulk metal halides (non-perovskite structures), and its effects on the physical and optoelectronic properties are demonstrated. While the optical properties change smoothly with doping, the electronic properties drop sharply above 10% Br and Cl doping. Based on this optimization method, the resulting metal halide TPVs exhibit device PCEs up to 1.22% and AVTs of 70.7%. Initial device stability studies further shed light on the influence of doping composition. Bromine doping was found to extend lifetime. This demonstrates that simple metal halide semiconductors are useful as light-harvesting materials for TPVs with high efficiency and transparency, and their bandgaps can be tuned to achieve ideal cutoff. Metal halides offer a potential approach to TPVs in a variety of applications due to their low cost and ease of processing.

[0112] [method] Material and precursor preparation: Dimethylformamide (DMF, anhydrous, 99.8%, Aldrich), PbI2 (99%, Aldrich), PbBr2 (99%, Aldrich), PbCl2 (98%, Aldrich), C 60(99.9%, MER Corporation.), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, Lumtech.), and tris-(8-hydroxyquinolinato) aluminum (Alq3, 99.5%, Lumtech.) were used as purchased. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT, Clevios PVP AI 4083, 1.3 wt.%, Heraeus) was diluted to 10 vol.% with deionized water before use. A 1.0 M PbI2 precursor solution was prepared by adding 461 mg of PbI2 to 1.0 mL of DMF. The solution was then stirred for 1 h and filtered through a 0.45 μm PTFE filter. Various concentrations of PbI2 solutions were prepared by diluting the 1 M PbI2 solution with DMF.

[0113] Device manufacturing: The PEDOT solution was spin-coated onto a pre-cleaned ITO substrate at 6000 rpm for 10 seconds, followed by annealing at 110 °C for 2 minutes. The lead halide precursor solution was spin-coated onto the PEDOT film at 6000 rpm for 7 seconds, then quickly transferred to a homemade vacuum chamber, depressurized to mTorr, and left for 3 minutes. The substrate was then transferred to a hotplate and annealed at 80 °C for 2 minutes. The substrate was then transferred to a deposition chamber and heated to 1000 °C. 60 (20 nm) and BCP (7.5 nm). Finally, a 5 nm thick silver electrode and 60 nm of Alq3 are deposited by thermal evaporation at a base pressure of 3 × 10 -6 Torr, and the final measured element area was 4.85 mm 2 For the opaque elements, a 80 nm silver layer is thermally evaporated onto the BCP layer as an electrode.

[0114] Measurements and Characterization: The thickness of the PbI2 film was measured using a spectroscopic ellipsometer (Wollam Vase). UV-VIS-NIR transmission and reflection spectra were measured using a dual-beam PerkinElmer Lambda 800 spectrometer. No reference sample was used for transmission measurements. Current density-voltage characteristics (JV curves) were obtained using a Keithley 2420 source measurement unit in the dark and under AM1.5G solar simulation. The light intensity was measured using an NREL-calibrated Si reference cell with a KG5 filter (xenon arc lamp; spectral mismatch factor for the studied device: 1.08 ± 0.02). The device was swept at 50 mV / s. EQE measurements were performed using a QTH lamp equipped with a calibrated Si detector, monochromator, chopper, and lock-in amplifier. IQE was estimated as IQE = EQE / (1 − RT). JV and EQE were measured on unencapsulated devices / samples in ambient air.

[0115] [result] PbI2 is a precursor material for lead halide perovskite films with a hexagonal crystal structure. PbI2 films are deposited on substrates by spin coating or thermal evaporation, and the thickness of the PbI2 film is controlled by varying the concentration of the precursor solution or the spin-coating speed (Figure 12A). First, the effect of PbI2 film thickness on device performance is investigated in an opaque device structure. PbI2 precursor solutions are prepared in the concentration range of 1 M to 0.1 M. As the solution concentration increases from 0.1 M to 1.0 M, the thickness of the PbI2 film increases from 9 ± 1 nm to 93 ± 2 nm (Figure 13). The processing atmosphere can have a significant effect on the morphology of the PbI2 film. Therefore, a vacuum-assisted method is used to fabricate highly reproducible and smooth PbI2 films. Scanning electron microscope (SEM) images show that the PbI2 films are uniform and smooth, with almost no pinholes (Figures 14A-14D). Figure 12B shows the device structure used. A thin layer of PEDOT acts as a hole transport layer. A 20 nm layer of fullerene is deposited on top of the PbI2 to act as an electron extraction layer. A thin layer of BCP is deposited on top of the fullerene to form an ohmic contact with an 80 nm thermally evaporated silver electrode. For transparent devices, the 80 nm silver electrode is replaced with a transparent electrode: 5 nm silver / 60 nm Alq3.

[0116] The device parameters for the opaque cells are summarized in Figures 12A-12D and Figures 15A-15B. The photocurrent of the device decreases with increasing PbI2 film thickness. The series resistance of the device increases with the PbI2 film thickness, and it is speculated that an appropriate charge collection length (or depletion width) of less than 40 nm induces increased charge recombination. The increase in series resistance leads to a decrease in the open circuit voltage (V OC ) also decreased, and V OC is less than 1.0 V (Fig. 15A). In contrast, V OC is typically 1.1V, with the highest recorded V OCThe PbI2 concentration is 1.17 V. The highest average PCE is 1.68% at approximately 0.4 M. This result is used as a guide for TPV fabrication. The goal is to utilize a sharp bandgap cutoff to more selectively harvest UV light. In some cases, a thick PbI2 film can reduce the transparency of TPV devices and the color appearance due to tail state absorption. Therefore, in this study, the concentration of the PbI2 precursor solution is constrained to less than 0.3 M, and the thickness of the PbI2 film in the TPV devices is less than 30 nm.

[0117] We further demonstrate that, surprisingly, despite their distinct crystal structures (hexagonal and perovskite), the absorption range of lead halide materials can be easily tuned by halogen doping, similar to that of perovskite films. This is useful because it allows precise tuning of the bandgap near the UV / VIS cutoff. Such bandgaps have been shown to be important for optimizing both PCE and AVT. Figure 16A shows photographs of PbI2 films with various bromine or chlorine doping ratios. As the Br or Cl doping amount increases, the pale yellow color fades to near colorless. Thus, the transparency of the films increases concomitantly (Figure 16B). A PbI2:PbBr2 ratio of 10:0 results in a yellow color, while a PbI2:PbBr2 ratio of 0:10 results in virtually no color. Figures 17A–17C show X-ray diffraction patterns (XRD patterns) of Br-doped lead halide films. The diffraction intensity increases when the molar doping rate is between 10 and 30%. This indicates that Br doping improves film crystallization. However, when the Cl doping rate increases beyond 10% and the Br doping rate increases beyond 30%, the performance of the corresponding device rapidly deteriorates (Figures 18A-18D). The doping optimization of TPV is performed with a limit of approximately 10% for both Cl and Br doping.

[0118] Lead halide TPVs were fabricated using bromine- or chlorine-doped (10%) PbI precursor solutions. The solution concentrations were 0.1 M, 0.2 M, and 0.3 M. A photograph of a fully assembled (unpatterned) TPV device is shown in Figure 19A. Quantitative transparency parameters for the TPVs, including AVT and CRI, are summarized in Table 3. Figures 19B and 19C show the transmittance spectra of PbI films and TPVs fabricated from various concentrations of lead halide precursor solutions. Figure 19B shows that the transmittance of the 0.1 M-PbI film is greater than 80% from 510 to 900 nm. Therefore, the peak transmittance of the 0.3 M-PbI film is approximately 70%, resulting in a decrease in the AVT of the TPV from 68.4% to 63.5% (Figure 19C). However, the highly colorless and transparent films obtained by the vacuum-assisted method exhibited all TPVs with AVT values ​​above 60% and no measurable haze (Table 3). The high transparency of undoped lead halide TPVs is partially attributable to the extremely thin lead halide films. However, doped lead halide films maintain higher transparency over a wider thickness range due to their band gaps closer to the 2.7-2.8 eV cutoff. Various lead halide films with the same precursor concentration have similar transmission spectra (particularly the transmission spectra of TPV devices) (Figures 20A-20B). For example, the transmission spectra of 0.2M films were all above 70% from 515 to 900 nm. The transmission spectra of TPV devices showed a peak at 520 nm. The transmittance at the peak was above 70%, and the AVT for 0.2M was approximately 68%.

[0119] [Table 3]

[0120] To investigate the optical properties, the reflectance spectra of the doped lead halide TPVs were also measured. 1.8 Br 0.2 The TPV device was used as a representative device. 1.8 Br 0.2A photograph of a TPV device taken outdoors is shown. The high CRI (over 90) indicates that there is no noticeable color change. Generally, the lower limit of acceptable color change for maintaining natural color is a CRI of 85-90. Figure 22A shows the PbI on ITO. 1.8 Br 0.2 film and PbI 1.8 Br 0.2 A photograph of the TPV device is shown. Figure 22B shows the corresponding PbI 1.8 Br 0.2 The transmission spectrum of the TPV is shown. Compared to the film itself, the transmittance of the TPV is reduced from 510 to 900 nm. This is mainly due to reflection (see Figure 21B). Typically, an anti-reflection layer (AR layer) can reduce the optical loss by about 3-4% on both sides of the device. An additional layer of AR coating on the glass surface reduces the optical loss of PbI 1.8 Br 0.2 The AVT of TPV increased from 67.5% to 69.1%. 1.8 Br 0.2 The AVT of TPV was over 70%.

[0121] To check the stationarity requirement, PbI 1.8 Br 0.2 The EQE of the TPV device is also shown in Figure 21B. The EQE of the device is 35% of the maximum at 410 nm. The integrated photocurrent calculated from the EQE spectrum is 1.78 mA cm -2 Considering that the calculated spectral mismatch factor is 1.09, the integrated value of this photocurrent is approximately equal to the short-circuit current density (J SC ) is in good agreement with the total absorbance. By estimating the total absorbance from the photon balance (A = 1 - TR), the maximum IQE is calculated to be 70.1% at 465 nm. Checking the consistency from the photon balance, the maximum sum of (T + R + EQE) was less than 1.0 at all wavelengths. Therefore, it is unlikely that these independently measured values ​​are overestimated.

[0122] The photovoltaic performance of lead halide TPVs is also systematically investigated as a function of doping and thickness (concentration). The photovoltaic parameters of the TPVs are summarized in Table 3 and plotted in Figures 23A–23D. The results show that the TPV devices are highly reproducible, with the majority of devices having PCEs greater than 1% (except for a few devices fabricated from 0.1 M precursor solutions). Overall, the lead halide TPVs exhibit improved device efficiency and transparency, with PCEs up to 1.22% and AVTs greater than 70%. Thus, we report TPV devices with AVTs greater than 70% and PCEs greater than 1%. Furthermore, by controlling both absorption and reflection, the CRI of the resulting devices is improved over that of the film itself. As a result, the devices exhibit more natural colors.

[0123] The initial stability of the unencapsulated TPVs is evaluated (see Figure 23D). All tested devices are able to maintain over 80% of their initial efficiency after 150 hours and over 60% of their initial efficiency after 500 hours. Among the TPVs investigated, PbI 1.8 Br 0.2 The devices were somewhat more stable in testing, a result similar to that seen with halide perovskites. Br-doped compositions and analogs generally tend to be more stable than pure iodide-based compositions, especially in air. Improved film crystallization also contributes to the stability of Br-doped TPV devices (see Figure 17C). With proper encapsulation, device lifetimes can be further improved, far beyond initial measurements in the encapsulated state.

[0124] In summary, a series of highly efficient and transparent lead halide TPV devices have been demonstrated. The thickness of the lead halide layer is systematically optimized. The bandgap and optical absorption of the lead halide film are also tuned by doping pure PbI2 with chlorine or bromine. The doping range is limited because device performance drops sharply above 10% for Cl doping and above 30% for Br doping. The results demonstrate the ability to tune the bandgap with these materials. After global optimization, the lead halide TPVs exhibit PCEs of over 1.0%, AVTs of over 70%, and CRIs of over 90. This is one of the highest device efficiencies reported at the highest transparency levels. It also paves the way for higher performance TPVs and multijunction TPVs using additional metal halides.

[0125] The above descriptions of the embodiments are provided for purposes of illustration and description. These descriptions are not intended to be exhaustive or to limit the present disclosure. Individual elements or features of specific embodiments are generally not limited to the specific embodiments and may be interchangeable where applicable. Furthermore, these elements or features may be used in selected embodiments even if not specifically set forth or described. These elements or features may be modified in various ways. Such variations should not be considered a departure from the present disclosure, and all such modifications are intended to be within the scope of the present disclosure.

Claims

1. A substrate; A first electrode; a homogeneous active layer including a light-absorbing material that absorbs only ultraviolet light (UV light) having a wavelength of less than 450 nm, the light-absorbing material being either (i) a halogenated perovskite containing two or more types of halogen atoms, or (ii) a metal halide; A second electrode; A transparent photovoltaic cell comprising: the first electrode is located between the substrate and the uniform active layer; the uniform active layer is located between the first electrode and the second electrode; the substrate, the first electrode, the uniform active layer, and the second electrode are all visibly transparent; The transparent photovoltaic cell has an average visible light transmittance of 50% or more; The transparent photovoltaic cell has a peak external quantum efficiency of 20% or more at wavelengths less than 450 nm. Transparent photovoltaic cells.

2. The light-absorbing substance is a metal halide, 10. The transparent photovoltaic cell of claim 1, having a peak external quantum efficiency of 30% or greater at wavelengths less than 450 nm.

3. The transparent photovoltaic battery has an average visible light transmittance of 50% or more, The transparent photovoltaic cell has a peak reflectance of more than 15% at a wavelength of 650 nm or more and 5000 nm or less. The transparent photovoltaic cell of claim 1.

4. 10. The transparent photovoltaic cell of claim 1, further comprising a first visible-transparent accessory layer located between the first electrode and the uniform active layer, the first visible-transparent accessory layer being an electron transport layer, an electron extraction layer, a hole blocking layer, or a buffer layer.

5. 5. The transparent photovoltaic cell of claim 4, wherein the first visible transparent accessory layer is an electron transport layer or an electron extraction layer that provides an ohmic contact between the homogeneous active layer and a first electrode.

6. The visible transparent first auxiliary layer may be made of fullerene, ZnO, TiO ２ , NiO, MoO ３ 5. The transparent photovoltaic cell of claim 4, comprising one or more of conductive nanotubes and conductive nanoparticles.

7. a second optically transparent auxiliary layer located between the uniform active layer and the second electrode; the first visible transparent accessory layer is an electron transport layer, an electron extraction layer, a hole blocking layer, or a buffer layer; the visibly transparent second accessory layer is an electron transport layer or an electron extraction layer; the visibly transparent second accessory layer is of a different type than the visibly transparent first accessory layer; The transparent photovoltaic cell of claim 4.

8. The transparent photovoltaic cell of claim 1 , wherein the uniform active layer is smooth.

9. The halogenated perovskite has the formula ABX ３ is expressed as wherein A is methylammonium (MA), formamidinium (FA), ethanediammonium (EA), isopropylammonium, dimethylammonium, guanidinium, piperidinium, pyridinium, pyrrolidinium, imidazolium, t-butylammonium, Na, K, Rb, Cs, or a combination thereof; B is Pb, Sn, Ge, Cu, Sr, Ti, Mn, Bi, Zn or a combination thereof; X is a combination of two or more halogen atoms; The transparent photovoltaic cell of claim 1.

10. The metal halide is PbI ２ , PbCl ２ , PbBr ２ , PbI Ｘ Br （１－Ｘ） , PbI Ｘ Cl （１－Ｘ） , PbBr Ｘ Cl （１－Ｘ） , Snl ２ , SnCl ２ , SnBr ２ , SnI Ｘ Br （１－Ｘ） , SnI Ｘ Cl （１－Ｘ） , SnBr Ｘ Cl （１－Ｘ） , GeI ２ , GeCl ２ , GeBr ２ , GeI Ｘ Br （１－Ｘ） , GeI Ｘ Cl （１－Ｘ） , GeBr Ｘ Cl[[ID=�3]] （１－Ｘ） , InI ３ , InCl ３ , InBr ３ , TiI ３ , TiCl ３ , TiBr ３ , GaI ３ , GaBr ３ , GaCl ３ , AlCl ３ , AlBr ３ , AlI ３ , A ２ , ATiI ６ , A ２ , ATiCl ６ and one or more of ATiBr ２ ６ are included,​ A is an alkali metal, an organic cation, or a combination thereof; wherein 0≦X≦1. The transparent photovoltaic cell of claim 1.

11. The transparent photovoltaic cell of claim 1, wherein the light-absorbing material satisfies either (i) or (ii) below: (i) the light-absorbing material is a halide perovskite; the halogenated perovskite includes nanocrystals; The nanocrystals have the formula ABX ３ is expressed as wherein A is methylammonium (MA), formamidinium (FA), ethanediammonium (EA), isopropylammonium, dimethylammonium, guanidinium, piperidinium, pyridinium, pyrrolidinium, imidazolium, t-butylammonium, Na, K, Rb, Cs, or a combination thereof; B is Pb, Sn, Ge, Cu, Sr, Ti, Mn, Bi, Zn or a combination thereof; X is a combination of two or more halogen atoms; (ii) the light-absorbing material is a metal halide; The metal halide has the formula BX ２ is expressed as wherein B is Pb, Sn, Ge, Cu, Sr, Ti, Mn, Bi, Zn or a combination thereof; X is a halogen or a combination of halogens.

12. 2. The transparent photovoltaic cell of claim 1, wherein the average visible light transmittance is 60% or greater.

13. 10. The transparent photovoltaic cell of claim 1, having a color rendering index greater than 80.

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