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EP-4742876-A2 - METHOD OF DEPOSITING A PEROVSKITE MATERIAL

EP4742876A2EP 4742876 A2EP4742876 A2EP 4742876A2EP-4742876-A2

Abstract

There is provided a method of producing a photovoltaic device comprising a photoactive region comprising a layer of perovskite material, wherein the layer of perovskite material is disposed on a surface that has a roughness average (R a ) or root mean square roughness (R rms ) of greater than or equal to 50 nm. The method comprises using vapour deposition to deposit a substantially continuous and conformal solid layer comprising one or more initial precursor compounds of the perovskite material, and subsequently treating the solid layer with one or more further precursor compounds to form a substantially continuous and conformal solid layer of the perovskite material on the rough surface. There is also provided a photovoltaic device comprising a photoactive region comprising a layer of perovskite material disposed using the method.

Inventors

  • KAMINO, Brett Akira
  • PEREZ, Laura Miranda

Assignees

  • Oxford Photovoltaics Limited

Dates

Publication Date
20260513
Application Date
20160610

Claims (12)

  1. A method of producing a photovoltaic device which has a multi-junction structure comprising a first sub-cell disposed over a second sub-cell, the first sub-cell comprising a photoactive region comprising a layer of perovskite material having the general formula [A][B][X] 3 where [A] is one or more monovalent cations, [B] is one or more divalent inorganic cations and [X] is one or more halide anions, wherein the layer of perovskite material is disposed on a surface that has a roughness average (R a ) or root mean square roughness (R rms ) of greater than or equal to 50 nm, and wherein an adjacent surface of the second sub-cell has a roughness average (R a ) or root mean square roughness (R rms ) of greater than or equal to 50 nm, and the rough surface on which the layer of perovskite material is disposed is a surface that conforms to the rough surface of the second sub-cell; wherein the rough surface of the second sub-cell comprises a surface of or within the second sub-cell that is provided with a surface texture, and the surface texture comprises one of pyramids and inverted pyramids having a range in height from 500 nm to 20 µm or from 1 µm to 10 µm; the method comprising depositing on said surface a perovskite layer, wherein depositing the perovskite layer comprises: a) using vapour deposition to deposit a substantially continuous and conformal solid layer comprising one or more initial precursor compounds of the perovskite material on the rough surface; the one or more initial precursor compounds comprising one of (i) a compound comprising a divalent inorganic cation B and a halide anion X, and (ii) a compound comprising a monovalent cation A and a halide anion X; and b) subsequently, treating the conformal solid layer comprising the one or more initial precursor compounds of the perovskite material using solution deposition with one or more further precursor compounds comprising the other of (i) a compound comprising a divalent inorganic cation B and a halide anion X and (ii) a compound comprising a monovalent cation A and a halide anion X, and thereby reacting the one or more initial precursor compounds and the one or more further precursor compounds to form a substantially continuous and conformal solid layer of the perovskite material on the rough surface.
  2. The method according to claim 1, wherein [X] comprises two different halide anions selected from fluoride, chloride, bromide, and iodide.
  3. The method according to claims 1 or 2, wherein the one or more monovalent cations, [A], comprises one or more organic cations selected from methylammonium (CH 3 NH 3 + ), formamidinium (HC(NH 2 ) 2 + ), and ethyl ammonium (CH 3 CH 2 NH 3 + ).
  4. The method according to any of claims 1 to 3, wherein the one or more monovalent cations, [A], comprises one or more monovalent inorganic cation selected from Cs + , Rb + , Cu + , Pd + , Pt + , Ag + , Au + , Rh + , and Ru + .
  5. The method according to any of claims 1 to 4, wherein the one or more monovalent cations, [A], comprises one or more monovalent organic cations selected from methylammonium (CH 3 NH 3 + ), formamidinium (HC(NH 2 ) 2 + ) and ethyl ammonium (CH 3 CH 2 NH 3 + ), in addition to one or more monovalent inorganic cations selected from Cs + , Rb + , Cu + , Pd + , Pt + , Ag + , Au + , Rh + , and Ru + .
  6. The method according to any of claims 1 to 5, wherein [B] comprises one or more divalent inorganic cations selected from Pb 2+ and Sn 2+ .
  7. The method according to any of claims 1 to 6, wherein each of the one or more initial precursor compounds comprises one of the one or more divalent inorganic cations [B] and each of the one or more further precursor compounds comprises one of the one or more monovalent cations [A].
  8. The method according to any of claims 1 to 6, wherein [A] comprises one or more inorganic cations, and each of the one or more initial precursor compounds comprises one of the one or more monovalent inorganic cations [A] and each of the one or more further precursor compounds comprises one of the one or more divalent inorganic cations [B].
  9. The method according to any preceding claims, wherein the surface on which the solid layer of perovskite material is disposed is any one of: an adjacent surface of the second sub-cell; and an adjacent surface of a layer that is disposed between the solid layer of perovskite material and the second sub-cell and that conforms to the rough surface of the second sub-cell.
  10. The method according to claim 9, wherein the solid layer of perovskite material is separated from the second sub-cell by one or more layers that each substantially conform to the rough surface of the second sub-cell.
  11. The method according to any preceding claim, wherein the thickness of the perovskite material is between 50 nm and 2 µm, preferably from 100 nm to 1000 nm, most preferably from 200 nm to 700 nm.
  12. The method according to any one of claims 1 to 10, wherein the thickness of the perovskite material is from 200 to 1000 nm, preferably from 300 to 1000 nm, more preferably from 300 to 700 nm, and even more preferably from 300 to 600 nm.

Description

FIELD OF THE INVENTION The present invention relates to a method of depositing a conformal layer of photoactive perovskite material onto a rough or textured surface, and photovoltaic devices that comprise a conformal layer of photoactive perovskite material disposed over a rough or textured surface. BACKGROUND OF THE INVENTION Over the past forty years or so there has been an increasing realisation of the need to replace fossil fuels with more secure sustainable energy sources. The new energy supply must also have low environmental impact, be highly efficient and be easy to use and cost effective to produce. To this end, solar energy is seen as one of the most promising technologies, nevertheless, the high cost of manufacturing devices that capture solar energy, including high material costs, has historically hindered its widespread use. Every solid has its own characteristic energy-band structure which determines a wide range of electrical characteristics. Electrons are able to transition from one energy band to another, but each transition requires a specific minimum energy and the amount of energy required will be different for different materials. The electrons acquire the energy needed for the transition by absorbing either a phonon (heat) or a photon (light). The term "band gap" refers to the energy difference range in a solid where no electron states can exist, and generally means the energy difference (in electron volts) between the top of the valence band and the bottom of the conduction band. The efficiency of a material used in a photovoltaic device, such as a solar cell, under normal sunlight conditions is a function of the band gap for that material. If the band gap is too high, most daylight photons cannot be absorbed; if it is too low, then most photons have much more energy than necessary to excite electrons across the band gap, and the rest will be wasted. The Shockley-Queisser limit refers to the theoretical maximum amount of electrical energy that can be extracted per photon of incoming light and is about 1.34eV. The focus of much of the recent work on photovoltaic devices has been the quest for materials which have a band gap as close as possible to this maximum. One class of photovoltaic materials that has attracted significant interest has been the hybrid organic-inorganic halide perovskites. Materials of this type form an ABX3 crystal structure which has been found to show a favourable band gap, a high absorption coefficient and long diffusion lengths, making such compounds ideal as an absorber in photovoltaic devices. Early examples of hybrid organic-inorganic metal halide perovskite materials are reported by Kojima, A. et al., 2009. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. Journal of the American Chemical Society, 131(17), pp.6050-1 in which such perovskites were used as the sensitizer in liquid electrolyte based photoelectrochemical cells. Kojima et al report that a highest obtained solar energy conversion efficiency (or power energy conversion efficiency, PCE) of 3.8%, although in this system the perovskite absorbers decayed rapidly and the cells dropped in performance after only 10 minutes. Subsequently, Lee, M.M. et al., 2012. Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites. Science (New York, N.Y.), 338(6107), pp.643-7 reported a "meso-superstructured solar cell" in which the liquid electrolyte was replaced with a solid-state hole conductor (or hole-transporting material, HTM), spiro-MeOTAD. Lee et al reported a significant increase in the conversion efficiency achieved, whilst also achieving greatly improved cell stability as a result of avoiding the use of a liquid solvent. In the examples described, CH3NH3PbI3 perovskite nanoparticles assume the role of the sensitizer within the photovoltaic cell, injecting electrons into a mesoscopic TiO2 scaffold and holes into the solid-state HTM. Both the TiO2 and the HTM act as selective contacts through which the charge carriers produced by photoexcitation of the perovskite nanoparticles are extracted. Further work described in WO2013/171517 disclosed how the use of mixed-anion perovskites as a sensitizer/absorber in photovoltaic devices, instead of single-anion perovskites, results in more stable and highly efficient photovoltaic devices. In particular, this document discloses that the superior stability of the mixed-anion perovskites is highlighted by the finding that the devices exhibit negligible colour bleaching during the device fabrication process, whilst also exhibiting full sun power conversion efficiency of over 10%. In comparison, equivalent single-anion perovskites are relatively unstable, with bleaching occurring quickly when fabricating films from the single halide perovskites in ambient conditions. More recently, WO2014/045021 described planar heterojunction (PHJ) photovoltaic devices comprising a thin film of a photoactive perovskite ab