Perovskite precursor composition, method of making a perovskite film, perovskite film and perovskite solar cell

Abstract

This invention relates to perovskite precursor compositions, methods for preparing perovskite films, perovskite films, and perovskite solar cells. The invention further relates to an ionic liquid (IL) comprising a perovskite precursor composition containing: a perovskite precursor; and a salt of a cationic imidazole derivative, wherein at least one of the two nitrogen atoms in the imidazole ring is attached to a carbon chain bearing a cyano group (-C≡N). The invention further relates to a perovskite solar cell with high stability comprising a layer composed of a perovskite film formed using the perovskite precursor composition of the invention.

Description

Technical Field

[0001] This invention relates to perovskite precursor compositions, methods for preparing perovskite films, perovskite films and perovskite solar cells, and more specifically, to perovskite precursor solutions for preparing humid air-stable perovskite layers and methods for depositing perovskite layers, and to solar cells obtained using such perovskite layers. Background Technology

[0002] Perovskite solar cells (PSCs) have made considerable progress, with the main improvement being in power conversion efficiency (PCE). Specifically, hybrid organic-inorganic perovskite light harvesters are a class of materials of interest, exhibiting suitable band gaps, high absorption coefficients, long charge mobility, and long diffusion lengths, while also being readily available and inexpensive to fabricate. Organic-inorganic lead halide perovskite solar cells (PSCs) have attracted increasing attention in recent years due to their surprisingly high PCE, ranging from 3.8% [Reference 1] to 25.2% [Reference 2]. However, the stability of PSC devices under operating conditions remains challenging. Numerous solutions have been proposed to address this issue.

[0003] (1) Doping 2-D perovskite into 3-D perovskite. For example, perovskite is treated with phenylethyl ammonium iodide (PEAI). PEAI can reach the surface of 3D perovskite and react with excess PbI2, which leads to the in-situ growth of PEA2PbI4 as a 2D perovskite interlayer. The 2D / 3D hybrid structure formed at the interface can significantly improve the performance of perovskite solar cells [References 4, 5];

[0004] (2) Adjusting the composition of the perovskite [Reference 6] or using a precursor without methylammonium iodide [Reference 7]. In addition, compositional substitution within the 3-D perovskite network can enhance hydrogen bonding within the 3D-perovskite structure, optimize the tilting of the PbI6 octahedral structure [Reference 8], and improve overall stability [Reference 9].

[0005] (3) Passivation techniques are employed [Reference 10]. Perovskite films can be passivated by fumigation [Reference 11] or by laser irradiation [Reference 12] to improve film uniformity and repair film defects, thereby increasing light collection. The use of volatile organic Lewis bases, such as pyridine [Reference 21] or gaseous methylamine [Reference 22], to passivate perovskite films has been reported.

[0006] In addition to the above methods, adding some additives to the perovskite precursor can improve the efficiency and stability of PSC:

[0007] (a) For example, incorporating large cations into the perovskite structure. Guanidine (Guanidinium) has been used as an effective large cationic additive to stabilize PSC with high PCE, thereby improving stability due to the formation of additional hydrogen bonds [Reference 13].

[0008] (b) Using imidazole-based compounds containing a fluorinated chain [Reference 14] or an allyl group [Reference 15] in the cation. Ionic liquid (IL) doping of perovskites can improve the quality of perovskite films, increase the hydrophobicity of the film surface, thereby preventing hydrolysis when exposed to moisture and thus increasing stability.

[0009] (c) Using self-polymerizable imidazole-based Ionic liquid-doped perovskites [Reference 16] can effectively incorporate a protective layer into the perovskite film, thereby allowing perovskite solar cells to be manufactured in air.

[0010] Ionic liquids (ILs) are non-volatile salts with high thermal and electrochemical stability, attributed to the strong electrostatic forces between their molecular ions. ILs have been widely used as additives [Reference 17].

[0011] References:

[0012] [1] Kojima, A. et al., J. Am. Chem. Soc. 131, 6050–6051 (2009);

[0013] [2]NREL, Best Research Cell-Efficiency: https: / / www.nrel.gov / pv / cell-efficiency.html

[0014] [3] Grancini, G.; Nazeeruddin, MK, Nature Reviews Materials2019, 4, 4. [3] Min, H.

[0015] [4] S Li, ​​L. Hu, C. Zhang, Y. Wu, Y. Liu, Q. Sun, Y. Cui, Y. Hao, Y. Wu, J. Mater. Chem. C, 2020, 8, 2425-2435.

[0016] [5] K. Lee, J. Kim, H. Yu, JW Lee, C.-M. Yoon, SKKim, J. Jang, J. Mater. Chem. A, 2018, 6, 24560.

[0017] [6]Min, H. et al., Science 2019, 366, 749.

[0018] [7]Gao, X.-X et al., Adv. Mater. 2020, 32, 1905502.

[0019] [8]R. Prasanna, A. Gold-Parker, T. Leijtens, B. Conings, A. Babayigit, H.-G. Boyen, M. F. Toney, M. D. McGehee, J. Am. Chem. Soc. 2017, 139, 11117.

[0020] [9]D. Ghosh, P. W. Atkins, M. S. Islam, A. B. Walker, C. Eames, ACS Energy Lett. 2017, 2, 2424.

[0021]

[10] Kanda, H.; Energy Environ. Sci. 2020, 13, 1222.

[0022]

[11] Z. Shao, Z. Wang, Z. Li, Y. Fan, H. Meng, R. Liu, Y. Wang, A. Hagfeldt, G. Cui, S. Pang, Angew. Chem. Int. Ed. 2019, 58, 5587.

[0023]

[12] X.-L. Trinh, N.-H. Tran, H. Seo, H.-C. Kim, Solar Energy, 2020, 206, 301.

[0024]

[13] Jodlowski, A. D. et al., Nat. Energy 2017, 2, 972.

[0025]

[14] R. Xia, Z Fei, N. Drigo, F. D. Bobbink, Z. Huang, R. Jasiūnas, M. V. Gulbinas, M. Mensi, X. Fang, C. Roldán-Carmona, M. K. Nazeeruddin, P. J. Dyson, Adv. Funct. Mater. 2019, 29, 1902021.

[0026]

[15] Y.Zhang,Z.Fei,P.Gao,Y.Lee,FFTirani,R.Scopelliti,Y.Feng,PJDyson,MKNazeeruddin,Adv.Mater.2017,29,170215。

[0027]

[16] X.Xia,X.-X.Gao,Y.Zhang,N.Drigo,V.Queloz,FFTirani,R.Scopelliti,Z.Huang,X.Fa ng,S.Kinge,Z.Fei,C.aRoldán-Carmona,MKNazeeruddin,PJDyson,Adv.Mater.2020,2003801

[0028]

[17] Torimoto,T.;Adv.Mater.2010,22,1196。

[0029]

[18] D.Zhao,Z.Fei,R.Scopelliti,PJDyson,Inorg.Chem.2004,43,2197。

[0030]

[19] Z.Fei,D.Zhao,D.Pieraccini,WHAng,TJGeldbach,R.Scopelliti,C.Chiappe,PJDyson,Organometallics 2007,26,1588。

[0031]

[20] Paul Dyson,Dongbin Zhao,Zhaofu Fei,WO2005 / 019185

[0032]

[21] NKNoel,A.Abate,SDStranks,ESParrott,VMBurlakov,A.Goriely,HJSnaith,ACS Nano 2014,8,9815。

[0033]

[22] Y.Zhang,G.Grancinia,Z.Fei,E.Shirzadi,X.Liu,E.Oveisic,FFTirani,R.Scopelliti,Y.Feng,MKNazeeruddin,PJDyson,Nano Energy,2019,58,105–111。

[0034]

[23] G. Sadoughi, DE Starr, E. Handick, SD: Stranks, M. Gorgoi, RG Wilks, M. H. J. Snaith, M. Baer, ​​ACS Appl. Mater. Interfaces 2015, 7, 13440. Summary of the Invention

[0035] The present invention was made primarily with the aim of providing improved stability to perovskite solar cells, particularly stability during long-term use and / or in the presence of air.

[0036] In a first aspect, the present invention therefore relates to perovskite precursor compositions comprising:

[0037] -Perovskite precursors; and

[0038] - A salt of a cationic imidazole derivative, wherein at least one of the two nitrogen atoms in the imidazole ring is attached to a carbon chain bearing a cyano group (-C≡N), wherein the cationic imidazole derivative has formula (1) or formula (2):

[0039]

[0040] In equation (1):

[0041] R 1 It is a C1-C4 alkyl group; and

[0042] R 2 It is –(CH2) n - where n is 2-6; and

[0043] In equation (2):

[0044] R 2a It is –(CH2) a - where a is 1-6; and

[0045] R 2b It is –(CH2) b - where b is 1-6.

[0046] R 1 It can be a C1-C3 alkyl group. R 1 It can be methyl. n can be 2 to 4. n can be 2 or 3. a can be 2 to 4. a can be 3. b can be 2 to 4. b can be 3.

[0047] Here, in the above-described perovskite precursor composition, the anionic counterion for the cationic imidazole derivative of formula (1) or formula (2) can be a halide anion, which is one or more of the following: Cl- , Br - and I - The halide anion can be Cl. - .

[0048] In a second aspect, the present invention relates to a perovskite precursor composition comprising:

[0049] -Perovskite precursors; and

[0050] - Salts of the cationic imidazole derivative of formula (1):

[0051]

[0052] In equation (1):

[0053] R 1 It is a C1-C6 alkyl group; and

[0054] R 2 It is –(CH2) n - where n is 1; and

[0055] The anionic counterion of the cationic imidazole derivative in formula (1) is chloride anion (Cl... - ).

[0056] R 1 It can be a C1-C3 alkyl group. R 1 It can be methyl.

[0057] In a preferred embodiment, the salt of the cationic imidazole derivative is one of the following:

[0058]

[0059] Ionic liquids with many types of nitrogen-containing side chains, such as imidazoles Salts of substances are widely used, primarily as solvents in catalytic reactions and for electrochemical applications. They can be prepared and obtained not only from counterions of halide anions (such as chloride, bromide, and iodide anions), but also from nitrate or acetate anions, dicyandiamide anions, or fluorinated anions such as BF4. - PF6 - Preparation and acquisition of trifluoromethanesulfonate, bis(trifluoromethanesulfonyl)imide, etc. The most preferred imidazole used in this invention is... The salts [C1CNmim]Cl, [C3CNmim]Cl, and [(C3CN)2im]Cl are all commercially available, for example, from suppliers such as Sigma-Aldrich, Alfa Chemistry, and ABClabtory Scientific. The synthesis methods for [C1CNmim]Cl and [C3CNmim]Cl have been further described in Zhao et al., Inorg. Chem. 2004, 43, 6, 2197–2205, and [(C3CN)2im]Cl has been further described in Zhao et al., Chem. Commun. 2004, 2500–2501. As another example of interest to this invention, [C4CNmim]Cl is commercially available from Chemieliva Pharmaceutical, and its synthesis is described in Zhao et al., Inorg. Chem. 2004, 43, 6, 2197–2205.

[0060] In the perovskite precursor composition of the present invention, in addition to using a salt of a cationic imidazole derivative (where at least one of the two nitrogen atoms in the imidazole ring is attached to a carbon chain with a cyano group (-C≡N)) as a perovskite precursor, ABX3 material can also be used, wherein:

[0061] A is an organic cation and / or a Group 1 metal cation, and the Group 1 metal cation is Cs and / or Rb;

[0062] B is selected from at least one of the following metals: Pb, Sn, Bi, Cu, Ag, and mixtures thereof; and

[0063] X is a halide anion, such as Cl, Br, I, and mixtures thereof.

[0064] The organic cation can be selected from at least one of the following: methylammonium (MA), butylammonium (BA), formamidinium. (FA) and guanidine (GUA). B can be Pb.

[0065] In a third aspect, the present invention relates to a method for preparing perovskite films, comprising the steps of:

[0066] (A) Preparation of the perovskite precursor composition of the first or second aspect;

[0067] (B) Provide the substrate; and

[0068] (C) A perovskite film is formed on the surface of the substrate.

[0069] In a fourth aspect, the present invention relates to perovskite films prepared by the method of the third aspect.

[0070] In a fifth aspect, the present invention relates to perovskite solar cells comprising:

[0071] (a) A transparent conductive layer;

[0072] (c) A perovskite film comprising a perovskite precursor composition of the first or second aspect; and

[0073] (e) Electrode,

[0074] Optionally further comprising one or more of the following: (b) an electron transport layer; (b') an electron blocking layer; (d) a hole transport layer; and (d') a hole blocking layer. Attached Figure Description

[0075] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein like symbols denote like elements, and wherein:

[0076] Figure 1A The molecular structures of ionic liquids (ILs) including [C1CNmim]Cl, [C3CNmim]Cl and [(C3CN)2im]Cl are shown.

[0077] Figure 1B The trication (Cs) with [C1CNmim]Cl was shown. 0.08 FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.12 3. Top view of the perovskite film using scanning electron microscopy (SEM).

[0078] Figure 1C The trication (Cs) with [C3CNmim]Cl was shown. 0.08 FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.12 3. Top view of the perovskite film using scanning electron microscopy (SEM).

[0079] Figure 1D It shows a trication (Cs) with [(C3CN)2im]Cl. 0.08 FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.12 3. Top view of the perovskite film using scanning electron microscopy (SEM).

[0080] Figure 1E Trications (Cs) without IL were shown. 0.08FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.12 3. Top-view SEM image of the perovskite film. The scale bar is 1 μm.

[0081] Figure 2A X-ray diffraction (XRD) patterns of perovskite films with [C1CNmim]Cl, [C3CNmim]Cl, [(C3CN)2im]Cl, and those without IL are shown, using a tricationic perovskite composition (Cs). 0.08 FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.12 3. All patterns were collected directly on the perovskite / SnO2 / mp-TiO2 / cp-TiO2 / FTO film, and the diffraction intensities are shown on the original scale. The right column shows magnified views of the (110) diffraction peak of perovskite and the (001) peak of PbI2.

[0082] Figure 2B Steady-state photoluminescence spectra of perovskite films with [C1CNmim]Cl, [C3CNmim]Cl, [(C3CN)2im]Cl and without IL are shown.

[0083] Figure 2C Time-resolved photoluminescence spectra of glass / perovskite coated perovskite films with [C1CNmim]Cl, [C3CNmim]Cl, [(C3CN)2im]Cl and without IL are shown.

[0084] Figure 3A High-resolution X-ray photoelectron spectroscopy (XPS) of perovskite films on FTO / cp-TiO2 / mp-TiO2 / SnO2 is shown, as well as Pb 4f spectra of perovskite films with [C3CNmim]Cl and those without IL after 3 days of storage in air (RH≈50%).

[0085] Figure 3B High-resolution X-ray photoelectron spectroscopy (XPS) of perovskite films on FTO / cp-TiO2 / mp-TiO2 / SnO2 and Pb 4f spectra of films with [C3CNmim]Cl and those without IL after heating in air at 150 °C for 30 min (RT = room temperature, HT = heating temperature) are shown.

[0086] Figure 4A A schematic diagram of the PSC device structure is shown.

[0087] Figure 4BPerformance comparisons of all types of PSCs are shown, including those with IL ([C1CNmim]Cl, [C3CNmim]Cl, [(C3CN)2im]Cl) and those without IL, as well as the JV curves of the device with the best performance during reverse scanning. The scan rate is 0.08 V / s. -1 The effective area is 0.16 cm². 2 .

[0088] Figure 4C Performance comparisons of all types of PSCs are shown, including those with IL ([C1CNmim]Cl, [C3CNmim]Cl, [(C3CN)2im]Cl) and those without IL, as well as the EQE spectra of the best-performing device and the Jsc curves of the integral of the best-performing device.

[0089] Figure 4D Performance comparisons of all types of PSCs are shown, including those with IL ([C1CNmim]Cl, [C3CNmim]Cl, [(C3CN)2im]Cl) and those without IL, as well as steady-state photocurrent output at the maximum power point.

[0090] Figure 4E Performance comparisons of all types of PSCs are shown, including those with IL ([C1CNmim]Cl, [C3CNmim]Cl, [(C3CN)2im]Cl) and those without IL, as well as stability studies of PSCs with and without IL under nitrogen for 1000 h without encapsulation, with PCE measured in situ. Detailed Implementation

[0091] In this invention, imidazole is used. Functionalized ILs containing CN functional groups in their cations are added as additives to the perovskite layer. Without being bound by any specific theory, it is believed that the pre-defined CN group in the IL cation can act as a Lewis base to coordinate to Pb(II) centers during the formation of the 3-D perovskite structure. Furthermore, it is believed that the coordination of CN groups to Pb(II) will compete with I / Br anions in the formation of the 3-D perovskite film, thereby slowing down the nucleation process and resulting in a film with increased uniformity and fewer defects. Cl anions can be encapsulated in the 3-D network to enhance hydrogen bonding and optimize structural tilt to increase stability. Different ILs with alkyl chains of varying lengths have been studied.

[0092] Based on the results of SEM, XRD, UV, and PL, the inventors concluded that regarding the effect of IL on photovoltaic performance, IL studied with cyano (CN) groups, compared with IL without CN groups, likely produced better film quality due to the coordination of CN groups to Pb(II) centers during the formation of the 3-D perovskite structure. Furthermore, Cl anions that can be encapsulated within the 3-D perovskite structure are believed to interact with methylammonium (MA) / formamidinium. The protons in the (FA) cation form significantly stronger hydrogen bonds, locking them in rigid positions and preventing phase transitions, thereby increasing stability. As a result, the PSC modified with CN-functionalized IL not only exhibits improved break-circuit voltage and fill factor, but also reduces the risk of environmental exposure, leading to a significant improvement in device stability.

[0093] <Organic-inorganic hybrid perovskite>

[0094] As used herein, the term "organic-inorganic hybrid perovskite," also referred to below as "hybrid perovskite," refers to ABX3 material, where A is an organic cationic group such as methylammonium (MA), butylammonium (BA), or formamidinium. (FA), or alkali metals Cs or Rb, and mixtures thereof; B is a metal such as Pb, Sn, Bi, Cu, Ag, and mixtures thereof; and X is a halide anion such as Cl, Br, I, and mixtures thereof. More generally, perovskites can be represented by formula A1. w A2 x A3 (1-w-x) B1 y B2 (1-y) X1 z X2 (3-z) This indicates that A1, A2, and A3 are the same or different organic cationic groups, such as methylammonium (MA), butylammonium (BA), and formamidinium. (FA), or alkali metal cation Cs + or Rb + Both w and x are 0 or greater and 1 or less; B1 and B2 are the same or different metals such as Pb, Sn, Bi, Cu, or Ag; y is 0 or greater and 1 or less; X1 and X2 are the same or different halide anions such as Cl, Br, or I; and z is 0 or greater and 1 or less. The preferred organic-inorganic hybrid perovskite of the present invention has lead (Pb) as the main metal B in molar terms, and most preferably lead (Pb) is the only metal B, such that the perovskite is Al. w A2 x A3 (1-w-x) PbX1 z X2 (3-z) Form. More preferably, X1 and X2 are Br and I.

[0095] Layered perovskites contain additional, larger molecules such as phenethylamine (PEA) or phenethylammonium, hexylammonium (HA), and longer-chain ammonium compounds, which confine different perovskite domains to different repeating units. Specific examples given herein include inorganic metal halide multilayer perovskites. These examples are not limiting.

[0096] In suitable perovskite (precursor) materials of the present invention, cesium (Cs) metal cations and organic cations such as formamidinium can be used. A combination of (FA) and / or methylammonium (MA). A particularly preferred cationic system is the tricationic system Cs-FA-MA. The anion used as the perovskite (precursor) material of the present invention may suitably comprise a mixture of iodide (I) and bromide (Br) anions. A particularly preferred peroxide precursor system is (Cs) 0.08 FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.12 3.

[0097] Perovskite precursor

[0098] The choice of perovskite precursor can determine the optoelectronic properties of the material, such as band gap energy, charge transport and / or binding energy, which affects the performance of the final device.

[0099] There are no particular limitations on the perovskite precursors used in the compositions of this invention.

[0100] In one implementation, the precursor is:

[0101] (A) at least one organohalogen compound and / or a cesium or rubidium halide; and

[0102] (B) At least one halide of a metal selected from the following: Pb, Sn, Bi, Cu, Ag and mixtures thereof, with Pb being the most preferred.

[0103] (A) At least one organohalide compound in the precursor may be selected, for example, from at least one of the following: methylammonium (MA), formamidinium (FA), phenylethylammonium (PEA) and guanidine (GUA). (B) Specific examples of metal halides in the precursors are PbCl2, PbBr2, and PbI2. It can be noted that metal carboxylates, especially lead carboxylate (Pb), such as Pb(CH3COO)2, can be used in place of metal halides.

[0104] Perovskite Coating Solution

[0105] Ionic liquids (ILs) have no vapor pressure and do not evaporate. In this respect, ILs are not traditional solvents; they can be removed after spin coating and will remain after aging at 100°C. Furthermore, ionic liquids can form eutectic liquids (mixtures of several ion pairs, such as cations MA, FA, and imidazole) with components derived from perovskite solutions. Cations, anions: I - Cl - The nucleation process in self-eutectic liquids is slower than that in pure DMSO or DMF.

[0106] In addition to the ionic liquid (IL) of the present invention, a solvent may be suitably added to the mixture of perovskite precursor components, and said solvent may be, for example, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), a combination of DMSO:DMF, γ-butyrolactone (GBL), N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), and acetonitrile (ACN).

[0107] Preferred solvents include, for example, DMSO, DMF, or γ-butyrolactone.

[0108] A suitable concentration of the perovskite precursor (in terms of Pb) is 0.6-1.4 M (mol / L). The suitable amount of functionalized IL dopant as a dopant in the perovskite precursor composition is 0.5-1.0 mol% of functionalized IL dopant relative to the amount of non-Cs or Rb perovskite metal atoms, for example, relative to the amount of Pb in most lead-based perovskites. An exemplary amount of functionalized IL dopant relative to the amount of perovskite metal atoms, such as Pb, is 0.75 mol%.

[0109] <Methods for preparing perovskite films>

[0110] In the method for preparing perovskite films according to the present invention, the method includes the steps of:

[0111] (A) Preparation of the perovskite precursor composition according to the present invention;

[0112] (B) Provide the substrate;

[0113] (C) A perovskite film is formed on the surface of the substrate.

[0114] Perovskite films can be formed, for example, by spin coating, printing, slot die coating, and meniscus coating. Slot die coating is preferred for large-area deposition.

[0115] In the above-described method for preparing a perovskite film according to the present invention, the substrate may suitably be a flexible or rigid conductive substrate.

[0116] In one aspect, the present invention further relates to perovskite films or layers prepared by the above method.

[0117] <Perovskite Solar Cells>

[0118] Perovskite solar cells can be fabricated, for example, using the perovskite film or layer of the present invention described above, and may include the following layers:

[0119] (a) A transparent conductive layer;

[0120] (c) Perovskite layer;

[0121] (e) Electrode layer.

[0122] Preferably, the perovskite solar cell may further comprise one or more of the following: (b) an electron transport layer; (b') an electron blocking layer; (d) a hole transport layer; and (d') a hole blocking layer.

[0123] The presence of at least one of these layers leads to higher device efficiency.

[0124] The three layers described above can be arranged in the order shown. Furthermore, the electron transport layer can be located between the transparent conductive layer and the perovskite layer, and the hole transport layer can be located between the perovskite layer and the electrode layer.

[0125] In one embodiment, the perovskite solar cell may have a conventional nip structure, which includes, in this order, a transparent conductive layer, an electron transport layer, a perovskite layer, a hole transport layer, and an electrode layer.

[0126] In another embodiment, the perovskite solar cell may have an inverted pin structure comprising, in this order, a transparent conductive layer, a hole transport layer, a perovskite layer, an electron transport layer, and an electrode layer.

[0127] In yet another embodiment, the perovskite solar cell may further include a mesoporous scaffold in the perovskite layer.

[0128] Typically, in a so-called pin or nip structure, an electron (n) or hole (p) blocking layer is sandwiched between the bottom and top of a perovskite layer (i), with the perovskite layer (i) in the middle. The mesoporous TiO2 layer is usually an electron transport layer (on the n side), but it can also be a hole transport layer (on the p side).

[0129] <(a) Transparent conductive layer>

[0130] There are no particular restrictions on the transparent conductive layer, and it may contain or be composed of the following: for example, fluorine-doped tin oxide (FTO), indium tin oxide (ITO), doped zinc oxide, carbon nanotube networks or graphene, with FTO being preferred.

[0131] <(b) Electron Transport Layer (ETL)>

[0132] There are no particular restrictions on the electron transport layer, and it may contain or be composed of the following: for example, TiO2, SnO2, Nb-doped SnO2, Sb-doped SnO2, C60 and C60 derivatives, bath copper spirit (BCP), a combination of C60 / BCP, and a combination of TiO2 / SnO2 bilayers.

[0133] Among these materials, the combination of TiO2 / SnO2 layers is preferred for nip structures, and the combination of C60 / BCP is preferred for pin structures.

[0134] <(b')hole blocking layer>

[0135] The optional hole-blocking layer can be, for example, 2,9-dimethyl-4,7-diphenyl-o-phenanthroline (BCP), TiO2, or ZnO.

[0136] When the electron transport layer (ETL) material is TiO2, assuming the layer is compacted, TiO2 simultaneously acts as both an electron transporter and a hole blocker. However, if the ETL material is mesoporous, the perovskite solution permeates and contacts the FTO electrode (which will result in losses). When the ETL material is mesoporous, to avoid direct contact between the perovskite and FTO, a compacted TiO2 layer can typically be advantageously incorporated between the FTO and the mesoporous TiO2 (barrier layer).

[0137] <(d') Electron blocking layer>

[0138] The optional electron blocking layer can be, for example, AlGaN.

[0139] <(d) Hole Transport Layer>

[0140] There are no particular restrictions on the hole transport layer, and it may contain or be composed of the following: for example, spiro-OMeTAD (2,2',7,7'-tetra-(N,N'-di-p-methoxyphenylamine)-9,9'-spirobisfluorene), pyrene-based materials (e.g., PY-1, PY-2, PY-3), tri-indene-based materials, phenothiazine-based materials, acridine, thiophene, biphenyl, bithiophene, tetrathiophene, difluorobenzene, and phenyl-based materials, triazine-based materials, benzotrithiophene and squaric acid-based materials, fluorene and spiro-fluorene-based materials, carbazole-based materials, phthalocyanine, carbon, metal complexes, CuNCS, NiO x , preferably spiral-OMeTAD.

[0141] <(e) Electrode layer>

[0142] There are no particular restrictions on the electrode layer, and it can contain or be composed of the following: for example, Au, C, Ag, Cu, or Al. Among these, Au is preferred on a laboratory scale because it is very efficient, but expensive. For industrial applications, carbon and Cu are preferred.

[0143] <Method for fabricating solar cell devices containing perovskite films>

[0144] The present invention also relates to a method for preparing a solar cell device comprising a perovskite film. The method of the present invention includes the following steps:

[0145] 1) Prepare a transparent conductive oxide layer;

[0146] 2) Optionally prepare and deposit an electron transport layer;

[0147] 3) Optionally prepare and deposit a hole-blocking layer;

[0148] 4) Preparation and deposition of perovskite layers;

[0149] 5) Optionally prepare and deposit an electron blocking layer

[0150] 6) Optionally prepare and deposit hole transport layers; and

[0151] 7) Prepare and deposit electrode layers.

[0152] <(1) Preparation of conductive oxide layer>

[0153] The conductive oxide layer can be prepared, for example, on FTO glass. In such a method, the etched FTO glass is cleaned, its surface is then treated, and it can subsequently be treated, for example, by spin-coating a TiO2 layer (which acts as an electron transport layer).

[0154] Those skilled in the art will recognize the appropriate preparation methods used for a given conductive oxide layer material.

[0155] <(2) Optional preparation and deposition of electron transport layer (ETL)>

[0156] The optional electron transport layer can be prepared, for example, with TiO2, such as by spin coating followed by annealing.

[0157] When the ETL material is TiO2, if the layer is compacted, TiO2 acts as both an electron transport and hole blocking material. However, if the ETL material is mesoporous, the perovskite solution can penetrate and contact the FTO electrode (which will result in losses). When the ETL material is mesoporous, to avoid direct contact between the perovskite and FTO, a compacted TiO2 layer is typically incorporated between the FTO and the mesoporous TiO2 (barrier layer). Therefore, optionally, the TiO2 barrier layer can be pre-deposited between the conductive layer and the electron transport layer.

[0158] <(3) Optional preparation and deposition of hole-blocking layers>

[0159] Those skilled in the art know of appropriate preparation methods for hole-blocking materials.

[0160] If the hole-blocking layer material is an organic material such as BCP, it can be prepared by solution (spin-coating with an organic solvent such as chlorobenzene) or by thermal sublimation.

[0161] If the hole-blocking layer material is an inorganic material such as TiO2, it can be prepared by spin-coating a precursor solution followed by thermal annealing. For example, a dilute solution of diisopropanol bis(acetylacetone)titanium in ethanol (Sigma-Aldrich) can be applied by spray pyrolysis at 450°C.

[0162] Those skilled in the art will recognize the appropriate preparation methods used for a given electron transport layer material.

[0163] <(4) Preparation and deposition of perovskite layer>

[0164] The perovskite solar layer can be deposited using the perovskite precursor solution disclosed above, through the method described above. This step can be performed in ambient air (temperature approximately 25°C and humidity approximately 30-50% RH).

[0165] Those skilled in the art will recognize the appropriate preparation methods used for a given perovskite layer material.

[0166] <(5) Optional preparation and deposition of electron blocking layers>

[0167] Those skilled in the art know the appropriate preparation methods for electron blocking materials.

[0168] If the electron blocking layer material is an organic material, it can be added from the solution (spin-coating), such as for spiro-OMeTAD, PEDOT:PSS, PolyTPD, PTAA.

[0169] If the electron blocking layer material is NiOx, it can be prepared by spin-coating a precursor solution followed by thermal annealing.

[0170] <(6) Optional preparation and deposition of hole transport layer (HTL)>

[0171] An optional hole transport layer can then be formed, for example, by spin-coating a solution containing spiro-OMeTAD. This step can be performed in ambient air (temperature approximately 25°C and humidity approximately 30-50% RH).

[0172] Those skilled in the art will recognize the appropriate preparation methods used for a given hole transport layer material.

[0173] <(7) Preparation and deposition of electrode layers>

[0174] The electrode layer can be prepared, for example, by gold (Au) vapor deposition.

[0175] Those skilled in the art know the appropriate preparation methods for electrode layer materials.

[0176] In the method for preparing a solar cell according to the invention, the method may suitably be carried out at a relative humidity of 10% or greater and 60% or less, preferably 20% or greater and 50% or less, more preferably 25% or greater and 45% or less, and most preferably 30% or greater and 40% or less.

[0177] In the method for preparing a solar cell according to the invention, in some embodiments, at least one of steps (1) and (3) can be performed at an ambient temperature of 15°C or higher and 30°C or lower, preferably 15°C or higher and 25°C or lower, and most preferably 20°C or higher and 25°C or lower. However, the temperature of the steps can vary. The perovskite-containing layer can be suitably deposited at ambient temperature and then annealed at a temperature of about 100°C. Depending on the material, steps (1) and (3) can or can not be performed at ambient temperature, but for example, commonly used TiO2 electron transport materials are deposited at ambient temperature and then annealed at a high temperature of 500°C. There are alternative options, such as SnO2 being deposited at 150°C.

[0178] Example

[0179] The present invention will be described in detail below with reference to the embodiments, but it is not believed that the scope of the present invention is limited to the embodiments described below.

[0180] Perovskite precursor solution

[0181] Precursor solutions: The precursor solutions (without IL) were prepared by dissolving PbI₂ (1.190 M, TCI), PbBr₂ (0.155 M, TCI), CsI (0.105 M, TCI), FAI (1.040 M, Dyesol), and MABr (0.155 M, Dyesol) in a mixed solvent DMF:DMSO = 4:1 (volume ratio). The precursor solutions containing IL were prepared by mixing PbI₂ (1.190 M, TCI), PbBr₂ (0.155 M, TCI), CsI (0.105 M, TCI), FAI (1.040 M, Dyesol), and MABr (0.155 M, Dyesol) with an equal molar amount of IL (0.75 mol%), and then mixing in DMF:DMSO = 4:1 (volume ratio).

[0182] Device fabrication

[0183] <Preparation of a transparent conductive layer>

[0184] Fluorine-doped tin oxide (FTO) coated glass substrate (Nippon Sheet Glass, TEC8) was cleaned for 10 minutes each in an ultrasonic bath using a detergent, deionized water, acetone, and isopropanol. The FTO substrate was then treated with a UV / ozone cleaner for 15 minutes before use.

[0185] <Preparation of TiO2 Barrier Layer>

[0186] The TiO2 compacted layer (cp-TiO2) was deposited onto a clean FTO substrate as follows: a diisopropanol bis(acetylacetone) titanium solution (75% in 2-propanol, Sigma-Aldrich, diluted 1:15 by volume in 2-propanol (99.8%, Acros Organics)) was sprayed and pyrolyzed at 450°C, followed by in-situ annealing for 30 min.

[0187] <Preparation and Deposition of Mesoporous Scaffold Layers and Electron Transport Layers>

[0188] The mesoporous TiO2 (mp-TiO2) solution consisted of 1 g of TiO2 paste (30NR-D, Greatcell Solar) diluted in 10 ml of anhydrous ethanol solution. The mesoporous TiO2 layer was then deposited onto an FTO / cp-TiO2 substrate via a one-step spin-coating process at 4500 rpm for 20 s. After annealing at 125 °C for 30 min, the mp-TiO2 films were gradually heated to 500 °C in air, and then baked at the same temperature for 20 min to remove organic components.

[0189] The SnO2 layer was prepared as follows: a 0.1M SnCl4 aqueous solution (99%, Acros Organics) was spin-coated at 3000 rpm for 20 seconds using a one-step method. The substrate was then transferred to a hot plate and heated at 150℃-190℃ for 1 hour. Before use, the FTO / cp-TiO2 / mp-TiO2 / SnO2 substrate was treated with UV / ozone for 30 minutes.

[0190] <Preparation and Deposition of Perovskite Layers>

[0191] Different types of perovskite precursors were spin-coated onto the top of an FTO / cp-TiO2 / mp-TiO2 / SnO2 substrate at 1000 rpm for 10 s and then at 5000 rpm for 30 s. In the second step, 100 μL of chlorobenzene was dropped onto the membrane at 15 s. The membrane was then annealed on a hot plate at 100 °C for 1 h. For all PSC devices, the perovskite absorber layer was thus prepared via a one-step spin-coating method. Once the perovskite membrane was fabricated, it was further treated with PEAI. Specifically, after cooling to room temperature, a phenylethyl ammonium iodide (PEAI) solution (14.9 mg / 1 mL) diluted in isopropanol (IPA) was spin-coated onto the substrate at 4000 rpm for 30 s.

[0192] <Preparation and Deposition of Hole Transport Layers>

[0193] The spiro-OMeTAD solution was prepared as follows: 4-tert-butylpyridine, Li[TFSI] in acetonitrile, and Co[t-BuPyPz]3[TFSI]3 (FK209, Dyesol) in acetonitrile were dissolved, and the molar ratio of spiro-OMeTAD:FK209:Li[TFSI]:TBP was 1:0.03:0.5:3.3. Subsequently, 40 μL of the spiro-OMeTAD solution was spin-coated onto a perovskite layer at 4000 rpm for 20 s to deposit as a hole transport layer (also referred to as a hole transport material (HTM) layer).

[0194] <Preparation and Deposition of Electrode Layers>

[0195] Finally, the Au electrode was deposited onto the hole transport material (HTM) layer with a thickness of 70 nm.

[0196] Grain morphology study

[0197] All functionalized ILs were used in the same amount (0.75 mol%) as trications (Cs). 0.08 FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.123) The effect of dopants in the perovskite precursor on the effect of IL (intensity filtration) varying with the number of CN groups and alkyl length was investigated. Perovskite solutions with different ILs were prepared using the methods described in the experimental examples section above. All samples were deposited on FTO / cp-TiO2 / mp-TiO2 / SnO2, and the films were then annealed on a hot plate at 100°C for 1 h.

[0198] Figure 1A The molecular structures of ionic liquids (ILs) including [C1CNmim]Cl, [C3CNmim]Cl and [(C3CN)2im]Cl are shown. Figure 1B-1E Trications (Cs) with different ILs were shown. 0.08 FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.12 3. Top view scanning electron microscope (SEM) images of perovskite films: (b) with [C1CNmim]Cl, (c) with [C3CNmim]Cl, (d) with [(C3CN)2im]Cl, (e) trications without IL (Cs 0.08 FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.12 3. Top-view SEM image of the perovskite film. The scale bar in the illustration is 1 μm.

[0199] like Figure 1B-1E As shown, when IL is introduced into the perovskite precursor, the trication (Cs) 0.08 FA 0.8 MA 0.12 )Pb(I 0.88 Br 0.12 )3. SEM images of the perovskite film show good coverage and clear grain morphology. Figure 1B-1D The grain sizes of the perovskite films are 320 nm (with [C1CNmim]Cl), 330 nm (with [C3CNmim]Cl), and 300 nm (with [(C3CN)2im]Cl). Conversely, the surface morphology of perovskites without IL consists of smaller crystals with an average size of 280 nm. Figure 1E ).

[0200] It has been reported that [BF4] has been added. - Low concentrations of IL can slightly increase grain size. This confirms that the presence of Cl... -The IL has the same beneficial effect during crystal growth. Furthermore, at the same dopant concentration, it has been shown that the grain size of perovskite films increases with increasing alkyl unit length and CN group number.

[0201] X-ray diffraction data and crystallinity study

[0202] In addition to morphology, X-ray diffraction (XRD) patterns ( Figure 2A The results show that all perovskite films exhibit similar characteristics, indicating that the introduction of low concentrations of IL did not significantly alter the perovskite structure. Typically, the ~12.6° peak is attributed to the (001) peak of PbI2, and the ~14.2° peak is attributed to the (110) peak of the perovskite.

[0203] It is known that a slow nucleation / crystallization process leads to large grain size and high crystallinity. Since the annealing steps are identical for all perovskite films, differences in grain size / crystallization can originate from the introduction of IL (inductance sulfide). Notably, films without IL exhibit the lowest crystallinity. Films with doped IL exhibit stronger diffraction, representing better crystallinity. As shown in the right column of the magnified view of the (110) diffraction peak of perovskite, the intensity of the (110) peak is significantly increased, indicating improved crystallinity of the perovskite film.

[0204] Furthermore, the crystallinity of the perovskite film increases with decreasing full width at half maximum (FWHM) value of the (110) peak. Consistent with previous reports, the "IL-free" film not only exhibits poor crystallinity but also shows poor crystallinity for formamidin. (FA) exhibits a tendency to transform into a yellow phase (δ-phase). However, the intensity of the main diffraction peak increases slightly with different doping of IL, and there is no peak at ~11.8°, indicating the increased crystallinity and excellent stability of the perovskite film. Interestingly, the (001) peak of PbI2 gradually disappears with increasing alkyl unit length and CN group number of IL.

[0205] Photoluminescence research

[0206] Steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements were performed to investigate nonradiative carrier recombination and charge separation or collection processes at the interface in perovskite films. The emission intensity of perovskite films with IL was significantly increased compared to those without IL. Figure 2B Specifically, [C3CNmim]Cl exhibits the highest PL intensity and is significantly better than that without IL. The UV-Vis absorption spectra of perovskite films with [C1CNmim]Cl, [C3CNmim]Cl, and [(C3CN)2im]Cl show that the band gaps of the perovskite films are similar to those without IL.

[0207] TRPL analysis was used to further verify the crystallinity quality of the perovskite film. A double-exponential fit was performed on the TRPL curves to quantify the support dynamics. Figure 2C As shown, the [C3CNmim]Cl doped perovskite film exhibits a long PL lifetime of 269.5 ns, while the PL lifetimes of the [C1CNmim]Cl doped film and the [(C3CN)2im]Cl doped perovskite film are 198.2 ns and 248.1 ns, respectively. However, the perovskite film without IL exhibits the shortest PL lifetime of only 117.7 ns. The large decrease in PL lifetime may also mean that the film with IL has significantly better crystal quality and fewer defect states compared to the film without IL. These results are consistent with SEM and steady-state PL measurements.

[0208] X-ray photoelectron spectroscopy (XPS) studies

[0209] X-ray photoelectron spectroscopy (XPS) was performed to probe the surface composition and chemical state of all films. Perovskite films containing [C3CNmim]Cl and those without IL were studied. The corresponding samples were placed in air at room temperature for 3 days (RH≈50%) and then the degradation products were detected. Figure 3A and 3B High-resolution XPS images of perovskite films on FTO / cp-TiO2 / mp-TiO2 / SnO2 are shown. Figure 3A The Pb4f spectra of perovskite films with [C3CNmim]Cl and those without IL are shown after 3 days of storage in air (RH≈50%). Figure 3B The Pb4f spectra of films with [C3CNmim]Cl and those without IL are shown after heating in air at 150°C for 30 minutes (RT = room temperature, HT = heating temperature).

[0210] like Figure 3A As shown, the main peaks at 138.5 eV and 143.4 eV can be attributed to the Pb–X (X: I, Br, Cl) bonds in the perovskite film, specifically Pb₄f₇ / ₂ and Pb₄f₅ / ₂, respectively. Interestingly, two additional peaks at lower binding energies (136.6 eV and 141.5 eV) are observed in the film without Il, which are attributed to metallic Pb. This confirms that the perovskite film with [C₃CNmim]Cl exhibits better air stability, thus reducing the risk of exposure to the atmosphere.

[0211] thermal stability

[0212] Furthermore, before XPS measurements, the thermal stability of films with and without IL was investigated by placing the films on a hot plate at 150°C in air for 30 minutes. This study showed that metallic Pb was detected in both samples. However, the ratio of metallic Pb in the perovskite without IL was higher than that with [C3CNmim]Cl, indicating that [C3CNmim]Cl effectively improves thermal stability. The formation of metallic Pb due to the presence of IL in perovskite films has not been routinely studied [Reference 23]. The low concentration of metallic Pb should be attributed to the improved film quality resulting from the application of IL as an additive. The presence of metallic Pb indicates the presence of iodide defects in the perovskite lattice of the samples. Additionally, the metallic Pb material in the film likely acts as a recombination center. As can be seen above, the introduction of IL ([C3CNmim]Cl) can simultaneously improve both air stability and thermal stability. The increased stability of perovskite films with [C3CNmim]Cl can be attributed to improved film quality, as the CN group in the cation competes with the I / Br anion in the formation of the 3-D perovskite network, resulting in a slower crystallization process and subsequently better quality. Introducing the Cl anion into the 3-D perovskite bulk strengthens hydrogen bonding, thereby preventing phase transitions and increasing stability.

[0213] Performance comparison of perovskite solar cells

[0214] Figure 4A The structure of the PSC used is shown, featuring an FTO / cp-TiO2 / mp-TiO2 / SnO2 / perovskite / PEAI / HTM / Au configuration. For all PSC devices, the perovskite absorber layer was prepared via a one-step spin-coating method, as shown in the experimental section. Once the perovskite film was fabricated, it was further treated with PEAI. SEM images show cross-sections of the devices. For comparison, devices were fabricated using different IL concentrations and the same fabrication method. The current density–voltage (J–V) curves for the optimal perovskite device were measured at AM1.5G. Figure 4B (and Table 1).

[0215] Figure 4B-4E Performance comparisons of all types of PSCs are shown, including those with IL ([C1CNmim]Cl, [C3CNmim]Cl, [(C3CN)2im]Cl) and those without IL. Figure 4B The JV curves for the device with optimal performance during reverse scanning are shown. The scan rate is 0.08 V / s. -1 The effective area is 0.16 cm². 2 . Figure 4C The EQE spectrum of the optimal performance device and the Jsc curve of the integral of the optimal performance device are shown. Figure 4DThe steady-state photocurrent output at the maximum power point is shown. Figure 4E The stability study of PSC with and without IL, measured in situ, is shown within 1000 h under nitrogen atmosphere without encapsulation.

[0216] It was observed that both the alkyl unit length and the number of CN groups in the ionic liquid (IL) affect the resulting membrane break voltage (Voc). The Voc of the PSC with IL increases from 1.09V (with [C1CNmim]Cl) to 1.15V (with [C3CNmim]Cl) and 1.15V (with [(C3CN)2im]Cl).

[0217] The short-circuit current density (Jsc) of the PSC with IL is similar (23.00 mA cm⁻¹). -2 (with [C1CNmim]Cl) up to 22.73 mA cm -2 (with [C3CNmim]Cl) and 22.21 mA cm -2 (with [(C3CN)2im]Cl)), which is lower than (23.30 mA cm) without IL. -2 ).

[0218] The fill factor (FF) of PSCs is sensitive to the quality of the perovskite layer, as well as the quality of the electron transport material (ETM) and hole transport material (HTM). PSCs with IL exhibit higher FFs, ranging from 0.810 (with [C1CNmim]Cl) to 0.819 (with [C3CNmim]Cl) and 0.815 (with [(C3CN)2im]Cl).

[0219] As can be seen above, among all devices doped with IL samples, the PSC doped with [C3CNmim]Cl exhibits the best performance compared to those doped with [C1CNmim]Cl (20.71%) and [(C3CN)2im]Cl (20.84%), with a power conversion efficiency (PCE) of 21.34%, all higher than those without IL (19.73%).

[0220] Therefore, it can be seen that perovskite solar cells doped with IL can achieve high overall performance. This improvement should be attributed to the reduced photogenerated charge recombination at the perovskite interface, as confirmed by PL measurements. Typically, the hysteresis phenomenon between forward and reverse scans is a key aspect for evaluating the overall performance of PSCs. Furthermore, devices based on perovskite with IL exhibit small hysteresis in both forward and reverse scan J–V curves. The PCE hysteresis is 3% for PSCs doped with [C3CNmim]Cl and 5% for PSCs without IL. These results indicate that doping with IL as an additive can provide high-performance PSCs with virtually eliminated hysteresis. Figure 4C The external quantum efficiency (EQE) and the corresponding spectral dependence of the integral current for PSCs under different conditions are shown. Clearly, all samples exhibit significantly higher EQE (~90%), which is attributed to the same transport layer. Furthermore, the trend of the integral current density across different devices is found to be consistent with that obtained from J–V measurements.

[0221] Table 1. Optimal device performance of perovskite solar cells with and without IL.

[0222]

[0223]

[0224] In terms of statistical results, twenty (20) devices were fabricated. Among devices doped with [C1CNmim]Cl, [(C3CN)2im]Cl, or perovskite devices without IL, the PSC doped with [C3CNmim]Cl exhibited significantly better performance. The histogram of the statistical efficiency distribution shows that the device doped with [C3CNmim]Cl exhibited superior performance with a narrow PCE distribution. Regarding device stability testing, the steady-state photocurrent density of the PSC was first measured at a fixed bias potential, with the maximum output power detected in the JV curve. The photocurrent output of devices with and without IL showed similar performance, and after 150 s, the device without IL showed only the smallest decrease compared to the device with IL. Figure 4D Then, the maximum power output (MPO) decay was evaluated for both IL-doped and undoped devices. All PSC devices were tested at 100 mW / cm². -2 The device was kept in a nitrogen atmosphere under constant illumination. Current-voltage curves (JV) were recorded every 2 hours. Clearly, the device doped with IL exhibited better stability than the device without IL. Figure 4EAfter 1000 hours of continuous light immersion, the MPO values ​​of the IL-doped devices remained at 86% (with [C1CNmim]Cl), 95% (with [C3CNmim]Cl), and 93% (with [(C3CN)2im]Cl), respectively. Conversely, the loss of PSCs without IL (70% of their initial values ​​after 1000 hours) was relatively high compared to the IL-doped devices. These stability data highlight the significant advantage of the long-term stability of PSCs resulting from the use of IL. It should be noted that additional treatment of the perovskite film with a PEAI layer can also benefit overall stability, as strong hydrogen bonding between the cations in IL and the protons and iodide anions in PEAI will be generated at the interlayer between the 3-D perovskite film, IL, and PEAI. Therefore, in a preferred embodiment of the invention, after depositing the perovskite film, the prepared perovskite film / layer is coated with a layer containing phenylethyl ammonium iodide (PEAI).

[0225] In summary, this has confirmed the presence of imidazole. The CN group on the alkyl side of the cation and the IL group of the halide anion (preferably Cl anion) can act as effective additives for perovskite precursors, especially tricationic (Cs, FA, MA) perovskite precursors, thereby achieving better stability in the resulting PSC device. (Imidazole linkage) Both the length of the alkyl unit in the ring and the number of CN groups affect the overall performance.

[0226] The effect of IL on the photovoltaic performance of PSC can be attributed to the completion effect of CN-to-I / Br anions during the formation of the 3-D perovskite film, resulting in better quality, and the encapsulation of Cl anions, which is attributed to the halide anion exchange Cl-I / Br, leading to enhanced hydrogen bonding and thus increased stability. These results indicate that doping PSC with CN-functionalized IL not only improves the break-circuit voltage and fill factor of PSC but also reduces the risk of exposure to the atmosphere, thereby leading to a significant improvement in device stability. The PSC device exhibits a high PCE of 21.34%, which is higher than that of the device without IL. Notably, after 1000 h of aging studies, the unencapsulated devices retained approximately 95% of their original efficiency.

Claims

1. A perovskite precursor composition, characterized in that it comprises: -Perovskite precursors; and - A salt of a cationic imidazole derivative, wherein at least one of the two nitrogen atoms in the imidazole ring is attached to a carbon chain bearing a cyano (-C≡N) group, wherein the cationic imidazole derivative has formula (1) or formula (2): in, In equation (1): R 1 It is a C1-C4 alkyl group; and R 2 It is –(CH2) n - where n is 2-6; and In equation (2): R 2a It is –(CH2) a - where a is 1-6; and R 2b It is –(CH2) b - where b is 1-6.

2. The perovskite precursor composition according to claim 1, characterized in that the anionic counterion of the cationic imidazole derivative of formula (1) or formula (2) is a halide anion, which is Cl... - ,Br - and I - One or more of them.

3. The perovskite precursor composition according to claim 1 or 2, characterized in that the salt of the cationic imidazole derivative is one of the following: 。 4. The perovskite precursor composition according to claim 1 or 2, characterized in that the perovskite precursor is ABX3 material, wherein: A is an organic cation and / or a Group 1 metal cation; and the Group 1 metal cation is Cs and / or Rb; B is selected from at least one of the following metals: Pb, Sn, Bi, Cu, Ag, and mixtures thereof; and X is selected from at least one of the following halogens: Cl, Br, I, and mixtures thereof.

5. The perovskite precursor composition according to claim 1 or 2, characterized in that it further contains a solvent, which is one or more of the following: DMSO or DMF or γ-butyrolactone.

6. A method for preparing perovskite films, characterized by comprising the following steps: (A) Preparation of a perovskite precursor composition according to any one of claims 1-5; (B) Provide the substrate; and (C) A perovskite film is formed on the surface of the substrate.

7. The method for preparing a perovskite film according to claim 6, characterized in that step (C) is performed by a method selected from: printing, slot die coating, meniscus coating, and spin coating.

8. The method according to claim 6 or 7, characterized in that the substrate is a flexible or rigid conductive substrate.

9. The method according to claim 6 or 7, characterized in that after forming the perovskite film, the perovskite film is coated with a layer containing phenylethyl-ammonium iodide (PEAI).

10. A perovskite film, characterized in that it is prepared by the method according to any one of claims 6-9.

11. A perovskite solar cell, characterized by comprising: (a) A transparent conductive layer; (c) A perovskite film comprising the perovskite precursor composition according to any one of claims 1-5; and (e) Electrode.

12. The perovskite solar cell according to claim 11, characterized in that it further comprises one or more of the following: (b) an electron transport layer; (b') an electron blocking layer; (d) a hole transport layer; and (d') a hole blocking layer.

13. The perovskite solar cell according to claim 11 or 12, characterized in that the transparent conductive layer (a) comprises one or more of the following: fluorine-doped tin oxide (FTO), indium tin oxide (ITO), doped zinc oxide, carbon nanotube network, and graphene.

14. The perovskite solar cell according to claim 12, characterized in that the electron transport layer (b) comprises one or more of the following: TiO2, SnO2, Nb-doped SnO2, Sb-doped SnO2, C60 and C60 derivatives, bath copper phosphate (BCP), a combination of C60 / BCP, and a combination of TiO2 / SnO2 bilayers.

15. The perovskite solar cell according to claim 12, characterized in that the hole transport layer (d) comprises one or more of the following: spiro-OMeTAD (2,2',7,7'-tetra-(N,N'-di-p-methoxyphenylamine)-9,9'-spirobisfluorene), pyrene-based materials, indene-based materials, phenothiazine-based materials, acridine, thiophene, biphenyl, bithiophene, tetrathiophene, difluorobenzene, and phenyl-based materials, triazine-based materials, benzotrithiophene and squaric acid-based materials, fluorene and spirofluorene-based materials, carbazole-based materials, phthalocyanine, carbon, metal complexes, and CuNCS, NiO x .

16. The perovskite solar cell according to claim 15, characterized in that the pyrene-based material is selected from PY-1, PY-2, and PY-3.

17. The perovskite solar cell according to claim 11 or 12, characterized in that the electrode (e) comprises one or more of the following: Au, C, Ag, Cu or Al.

18. The perovskite solar cell according to claim 11 or 12, characterized in that the perovskite solar cell further comprises a mesoporous support having a nip or pin structure.

19. The perovskite solar cell according to claim 12, characterized in that the perovskite film (c) is coated with a layer containing phenylethyl ammonium iodide (PEAI), the PEAI-containing layer being located between the perovskite film (c) and the hole transport layer (d), and also between the perovskite film (c) and the electrode (e).

Images