Perovskite layer, preparation method thereof and photoelectric device

Abstract

The invention relates to a perovskite layer, a preparation method thereof and a photoelectric device. The perovskite layer of the present application includes a perovskite compound and a surfactant, where the perovskite compound is represented by Formula 1: (A +) 1-y (A '+) y (M2 +) (X-) 3, where y is 0.01-0.99; m < 2 + > is Pb < 2 + >, Sn < 2 + > or Ge2 +; each of A + and A '+ is independently Cs +, Rb +, CH3NH3 +, CH3CH2NH3 +, H (C = NH2) NH2 +, or Me (C = NH2) NH2 +; and X-is independently in each case F-, Cl-, Br-or I-wherein A + and A '+ are the same or different; and the surfactant comprises a sulfonate surfactant, an alcohol alkoxylate surfactant, a quaternary ammonium surfactant, or a mixture thereof. The photoelectric device comprising the perovskite layer can achieve improved power conversion efficiency (PCE) while also maintaining the stability of the PCE in the device.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to perovskite layers, methods of making the same, and optoelectronic devices. BACKGROUND

[0002] Perovskite solar cells (PSCs) are considered one of the most promising photovoltaic technologies for the future with a wide range of application scenarios, including building integrated photovoltaics, because it combines the advantages of potentially low manufacturing cost and high power conversion efficiency (PCE). In recent years, the certified record PCE of PSCs has rapidly climbed, continuously injecting vitality into the photovoltaic industry. However, the long-term durability of PSCs under real operating conditions with complex stressors of light, heat, and moisture remains a prominent issue, requiring in-depth fundamental research on the relationship between microstructure and performance. A large number of studies have shown that the device heterointerfaces play a dominant role in the long-term durability of PSCs. Therefore, achieving ideal microstructure and functional integrity on the device heterointerfaces is a key step to optimize carrier injection and thermal management to minimize moisture ingress and mitigate mechanical damage due to interface fatigue and accumulated thermal stress.

[0003] Research on interface engineering has mainly focused on chemical passivation of the perovskite top surface and bottom (also referred to as “buried”) surface / interfacial, thereby reducing defect density, manipulating energy level alignment, improving phase purity, etc. However, in-depth understanding of the microstructural integrity of these heterointerfaces is often missing, which ultimately determines the functional characteristics. In particular, perovskite heterointerfaces are generally considered to be ideal continuous and flat microstructure types. In fact, the perovskite thin films in current PSCs are polycrystalline, consisting of densely packed individual crystalline grains.

[0004] However, the current research on the surface microstructure of perovskite films, especially on the microstructure of individual crystalline grains that make up the perovskite film, is not yet in-depth. In addition, there is still a need to further improve the power conversion efficiency (PCE) and stability of PCE of the devices. The subject matter described herein addresses this unmet need. SUMMARY

[0005] The present disclosure provides strategies for improving the surface of perovskite materials to enhance their performance in photovoltaic devices.

[0006] In a first aspect, provided herein is a perovskite layer comprising a perovskite compound and a surfactant, wherein the perovskite compound is represented by Formula 1:

[0007] (A + ) 1-y (A’ + ) y (M 2+ )(X - )3 1

[0009] wherein y is 0.01-0.99;

[0010] M 2+ is Pb 2+ , Sn 2+ or Ge 2+ ;

[0011] A + and A’ + are each independently Cs + , Rb + , CH3NH3 + , CH3CH2NH3 + , H(C=NH2)NH2 + or Me(C=NH2)NH2 + ; and

[0012] X - is independently at each occurrence F - , Cl - , Br - or I - , wherein A + and A’ + are the same or different; and

[0013] The surfactant comprises a sulfonate surfactant, an alcohol alkoxylate surfactant, a quaternary ammonium surfactant, or a mixture thereof.

[0014] In certain embodiments, the sulfonate surfactant comprises a sulfonic acid group substituted with a halo-C4-C 12 alkyl group.

[0015] In certain embodiments, the quaternary ammonium surfactant comprises one or more C1-C 16 alkyl substituents.

[0016] In certain embodiments, the surfactant comprises one or more of: potassium tridecafluorohexane-1-sulfonate, sodium tridecafluorohexane-1-sulfonate, potassium perfluorobutane-1-sulfonate, sodium perfluorobutane-1-sulfonate, potassium perfluorodecane-1-sulfonate, sodium perfluorodecane-1-sulfonate, poly(ethylene oxide) / poly(propylene oxide) (EO / PO) block copolymer, or N,N,N-Trimethyloctan-1-aminium chloride (NTAC).

[0017] In certain embodiments, M2+ It is Pb 2+ And A + and A' + Each of them is independently Cs + CH3NH3 + or H(C=NH2)NH2 + .

[0018] In some embodiments, the perovskite layer contains (H(C=NH2)NH2) + ) 1-y (Cs + ) y (Pb 2+ (I) - )3, where y is 0.01-0.99.

[0019] In some embodiments, the perovskite layer comprises perovskite of formula 2:

[0020] [(A + ) 1-y (A' + ) y (M 2+ (X) - )3] 1-z [(A” + )(M' 2+ (Q) - )3] z 2

[0022] Where y is 0.01-0.99;

[0023] z is 0.01-0.99;

[0024] M 2+ It is Pb 2+ Sn 2+ Or Ge 2+ ;

[0025] M' 2+ It is Pb 2+ Sn 2+ Or Ge 2+ ;

[0026] A + A' + and A” + Each of them is independently Cs + 、Rb + CH3NH3 + CH3CH2NH3 + H(C=NH2)NH2 + Or Me(C=NH2)NH2+ ; and

[0027] X - and Q - are independently in each case F - , Cl - , Br - , or I - , wherein A + and A’ + are the same or different.

[0028] In certain embodiments, each of M 2+ and M’ 2+ is Pb 2+ ; each of A + and A’ + is independently Cs + , CH3NH3 + , or H(C=NH2)NH2 + ; and A” + is CH3NH3 + .

[0029] In certain embodiments, the perovskite layer comprises [(H(C=NH2)NH2 + ) 1-y (Cs + ) y (Pb 2+ )(I - )3] 1-z [(CH3NH3 + )(Pb 2+ )(Br - )3] z , wherein y is 0.01-0.99 and z is 0.01-0.99.

[0030] In certain embodiments, the perovskite layer comprises a plurality of perovskite grains, and a bottom surface of each of the plurality of perovskite grains comprises a single grain surface concave (GSC) and a ridge surrounding the GSC, and wherein an average angle ξ between a line connecting a ridge apex and a GSC center and a top surface opposite the grain bottom surface of the perovskite grain is 0°-1.5°.

[0031] In certain embodiments, the perovskite layer comprises a plurality of perovskite grains and a grain-boundary grooving (GBG) between a bottom surface of each adjacent perovskite grain, the GBG being surrounded by edges of the adjacent perovskite grains as GBG sidewalls, and wherein an average angle Θ of the perovskite grains between a tangent to the GBG sidewall and a top surface opposite the grain bottom surface is 0°-15°.

[0032] In a second aspect, provided herein is a method for producing the perovskite layer in the first aspect, wherein the method comprises:

[0033] providing a perovskite precursor solution, the solution comprising one or more metal salts each independently represented by the formula MX2, two or more salts each independently represented by the formula AZ, a surfactant, and a solvent, wherein M is Pb 2+ , Sn 2+ or Ge 2 + , A is Cs + , Rb + , CH3NH3 + , CH3CH2NH3 + , H(C=NH2)NH2 + or Me(C=NH2)NH2 + , X is independently at each occurrence F - , Cl - , Br - or I - , and Z is independently at each occurrence F - , Cl - , Br - or I - ;

[0034] depositing the perovskite precursor solution on a surface of a charge-transport layer (CTL) to form a wet film; and

[0035] annealing the wet film to form the perovskite layer.

[0036] In certain embodiments, wherein the perovskite precursor solution comprises (Cs + )(I - ), (H(C=NH2)NH2 + )(I - ), (Pb 2+ )(I - )2, and perfluorohexane-1-sulfonate.

[0037] In certain embodiments, wherein the perovskite precursor solution comprises (Cs+ )(I - ), (H(C=NH2)NH2 + )(I - ), (CH3NH3 + )(Cl - ), (Pb 2+ )(I - )2, (CH3NH3 + )(Pb 2+ )(Br - )3, and perfluorohexane-1-sulfonate.

[0038] In certain embodiments, the surfactant has a concentration of 0.1-5 mg / ml in the perovskite precursor solution.

[0039] In certain embodiments, the one or more metal salts have a concentration of 0.5-2.0 M in the perovskite precursor solution.

[0040] In a third aspect, provided herein is an optoelectronic device comprising the perovskite layer of the first aspect.

[0041] In certain embodiments, the optoelectronic device is a perovskite solar cell (PSC), a perovskite light-emitting diode, a perovskite laser, or a perovskite photodetector.

[0042] In certain embodiments, the perovskite solar cell comprises an interfacial glue layer between the perovskite compound film and an adjacent charge transport layer.

[0043] In certain embodiments, the perovskite solar cell has a photoelectric conversion efficiency of 23.5-25.5%. BRIEF DESCRIPTION OF DRAWINGS

[0044] The foregoing aspects and many of the attendant advantages of this application will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings.

[0045] Figure 1Geometrical features and chemical accommodation of GSC microstructure at perovskite grain-CTL microheterointerfaces are depicted. a, b, AFM topography of perovskite film bottom surfaces with (a) and without (b) GSC at the grain-CTL heterointerface. c-f, 2D (c, d) and 3D (e, f) AFM images of selected areas (dotted lines) in perovskite film bottom surfaces with (c) and without (d) GSC. g, h, 2D surface height line profiles (guided by dotted lines) on perovskite film bottom surfaces with (g) and without (h) GSC. i, Schematic diagram showing the surface topography of a perovskite grain flipped at the heterointerface. Angles shown using dotted lines correspond to GBG angle Θ and GSC angle ξ, respectively. j, Statistical distribution of GBG angle Θ for perovskite films with (sample size, n = 40) and without (n = 40) GSC. k, Statistical distribution of GSC angle ξ for perovskite films with (sample size n = 30) and without (sample size n = 30) GSC. Box plots show the mean, median, upper and lower hinges, 25-75% box limits, and 1.5 x interquartile range whiskers.

[0046] Figure 2 Microstructure evolution of GSC at perovskite grain-CTL microinterfaces is depicted. a, Schematic diagram of microstructure evolution of GSC. b, Schematic diagram of the role of potassium perfluorohexane-1-sulfonate (TFSAP) in accommodating GSC. c, Determined surface free energy γs, GB energy γgb, and Δγ in perovskite grains with and without GSC. d, Normalized out-of-plane deformation εz in perovskite grains with and without GSC.

[0047] Figure 3Photoelectric, chemical, heat transport, and thermo-mechanical properties of perovskite grain-CTL microinterfaces are depicted. a, Stable PL spectra of perovskite films with and without GSC. b, Normalized TRPL spectra and bi-exponential fitting lines of perovskite films with and without GSC. c, Current-voltage (I-V) curves and exponential fitting lines of ohmic and trap-filled limited regions of a capacitor-like perovskite device with ITO / Sn02 / perovskite / PCBM / Ag structure. d-e, Ultraviolet-visible (UV-vis) absorption changes of perovskite films with and without GSC, respectively, under 120 h rigorous light-heat testing (3 suns intensity illumination; 80 °C). The insets are optical photographs of degraded perovskite films after testing. f-g, Normalized change in transmission differential (dT / T) spectra of perovskite samples with and without GSC, respectively, at different pump delay times (30 ns to 90 ns). h, FEA temperature distribution of grain-CTL microinterfaces with (top) and without (bottom) GSC. The scale bar is 100 nm. In this case of internal heat source, a temperature gradient is set from the top surface of the grain (85 °C) to the bottom surface of the Sn02layer (20 °C). i, Schematic of the delamination process for quantitatively determining the mechanical reliability of perovskite-CTL heterointerfaces. A standard perovskite grid is pre-fabricated on the perovskite film by a blade array, followed by the delamination process. The ratio of the delaminated area on the epoxy resin reflects the toughness level of the heterointerface. j, k, Optical photographs showing the remaining area of perovskite films on the CTL surface after the delamination process with and without GSC, respectively. 1, Statistical distribution of normalized delaminated area A d of perovskite films with GSC (original, sample size n = 21; with I-SAM, sample size n = 7) and without GSC (original, sample size n = 22; with I-SAM, sample size n = 9) after the delamination process. Box plots show the mean, median, upper and lower minimum and maximum, 25-75% box limits, and 1.5 x interquartile range whiskers. m, Statistical distribution of the rating (0B-5B) of interfacial adhesion based on the normalized delaminated area according to the ASTM D3359 standard. 0B represents an area removed from the substrate greater than 65%, corresponding to the worst interfacial strength. IB, 2B, 3B, and 4B represent removed areas of 35%-65%, 15%-25%, 5%-15%, and less than 5%, respectively. 5B represents no remaining area on the substrate after delamination, corresponding to the strongest interfacial strength.

[0048] Figure 4 depicts PCE and durability of PSC devices with and without GSC at perovskite grain-CTL microinterfaces. a-b, J-V curves (a) and EQE spectra (b) with integrated J SC voltage (V) of the best PSCs with and without GSC. The device structure is ITO / Sn02 / (FA0.95 Cs 0.05 PbI3) 0.975 (MAPbBr3) 0.025 Perovskite / Spiro-OMeTAD / Au. The inset table in (a) shows the extracted J-V parameters. c, PCE statistical distribution based on a total of 30 PSC devices with and without GSC. d, Thermal cycling durability (between -40 °C and +85 °C) of PSCs with and without GSC based on ISOS-T-3 protocol. e, Humidity-heat durability of PSCs with and without GSC based on ISOS-D-3 protocol (85 °C; 85% RH). f, MPP tracking of PSCs with / without GSC based on ISOS-L-l l protocol (one sun intensity illumination; in N2). N2 flow was used to dissipate heat from the device surface, maintaining the temperature around 40-50 °C. Device structure for d-f is ITO / Sn02 / FA 0.9 Cs 0.1 PbI3perovskite / PTAA / Au. g, Schematic illustration of strain evolution of perovskite film during -40 °C to 85 °C thermal cycling, which can easily lead to interfacial delamination at the grain-CTL micro-heterointerface in the presence of GSC due to the accumulated thermal stress on the ridges, as shown in the right panel. h, Schematic illustration of the role of GSC at the micro-heterointerface during humidity-heat testing. i, Schematic illustration of photothermal decomposition, which can easily occur at the free surface exposed to GSC.

[0049] Figure 5 Schematic illustration of the peeling process of perovskite film, and the morphological features of the bottom interface of perovskite film.

[0050] Figure 6 AFM topography of the surface of Sn02film is depicted. 2 x 2 pm2 2 AFM height image. The dotted box highlights the tiny grains remaining on the Sn02surface, which correspond to Figure 1 In-grain holes in (a).

[0051] Figure 7 are top-view SEM images of the bottom surface of perovskite film with (a) and without (b) GSC.

[0052] Figure 8 are cross-sectional SEM images of perovskite grain-CTL heterointerface with (a) and without (b) GSC.

[0053] Figure 9Geometric parameter comparison of the Sn02top surface and the grain bottom surface is depicted. Statistical distribution of the length (a) and height (b) local fluctuations of the Sn02top microsurfaces (length, n = 25; height, n = 50) and the grain bottom microsurfaces (length, n = 25; height, n = 50) in the target set without GSC. Boxplots show the mean, median, upper and lower extremes, 25-75% box limits and 1.5 x interquartile range whiskers.

[0054] Figure 10 AFM topography (1 x 1 pm2) of the perovskite film bottom surface of the target sample before (a) and after (b) IPA washing is depicted. 2 ).

[0055] Figure 11 AFM height images of the top surface of the perovskite film with (a) and without (b) GSC are depicted.

[0056] Figure 12 Evidence of GSC presence in perovskite films on different substrates is shown. a-d, AFM topography (2 x 2 pm2) of the FTO substrate surface (a), silicon wafer substrate surface (b) and perovskite bottom surface fabricated on FTO (c) and silicon wafer (d). e-f, 2D height profiles guided by the dashed lines in c (e) and d (f). 2 ). Figure 12 c (e) and d (f). Figure 12

[0057] Figure 13 Comparison of the Sn02protrusion height and GSC depth is shown. a, Statistical distribution of the Sn02protrusion height and GSC depth based on a total of 100 measurements. Boxplots show the mean, median, upper and lower extremes, 25-75% box limits and 1.5 x interquartile range whiskers. b-c, Schematic representation of the grain formation with GSC of different depths.

[0058] Figure 14 Evidence of residual perovskite nanofragments on the Sn02surface corresponding to GBG on the perovskite bottom surface is shown. 2D height profiles of the residual perovskite nanophases on the Sn02top surface (guided by the dashed lines) and the depressions in the GBG region on the perovskite bottom surface (guided by the dashed lines). The AFM height image of the perovskite bottom surface in the lower left corner is taken from Figure 1 a. The AFM height image of the Sn02surface in the upper right corner is taken from Figure 6 b.

[0059] Figure 15 ​Presence of GSC in perovskite films with KI additive is shown. a, AFM topography of the bottom surface of perovskite film for the sample with additive KI (same concentration as TFSAP). b, 2D surface height profile guided by the dashed line in a.

[0060] Figure 16 Contact angle results used to calculate surface free energy are shown. Contact angles of H2O on perovskite films with (a) and without (b) GSC; and contact angles of diiodomethane (CH2I2) on perovskite films with (a) and without (d) GSC.

[0061] Figure 17 Mechanism of ion flow and its blocking by anchoring surfactant molecules is depicted. Schematic of solid state ion flow via vacancies at GB and grain surface (a), inhibitory effect of anchoring surfactant molecules on ion flow (b), and effect of size of passivating molecules on ion flow inhibition (c). Solid state ion diffusion is mainly mediated by surface / interface vacancies. Functional groups of surfactant molecules with rich electron pairs can passivate defects in perovskite to hinder ion flow. Mobile ions have to push the molecules kinetically to achieve diffusion. Larger passivating molecules will be more difficult to be replaced, leading to more effective inhibition of solid state ion migration.

[0062] Figure 18 Two other surfactant additives are depicted to minimize GSC on perovskite bottom surface. a, Molecular structures of P123 (P123) and NTAC. b-c, AFM topography of perovskite film bottom surface at perovskite-CTL heterointerface with addition of P123 (b) and NTAC (c) to precursor solution.

[0063] Figure 19 Stable PL intensity of glass / Sn02 / perovskite structure is depicted. Stable PL intensity of perovskite films with and without GSC with glass / Sn02 / perovskite structure.

[0064] Figure 20 PL and TRPL decay of exposed buried perovskite surface is depicted. a-b, PL (a) and TRPL (b) spectra of delaminated perovskite films (exposed buried surface) with and without GSC. The photo-carrier lifetime (578 ns) fitted from the TRPL spectrum of the target film is longer than that of the original film (99 ns).

[0065] Figure 21Backside PL and TRPL decay of quartz / Sn02 / perovskite structure are depicted. Backside PL (a) and TRPL (b) spectra of samples with and without GSC (quartz / Sn02 / perovskite structure). τ avg Decreased from 55 ns for the original film to 18 ns for the target film.

[0066] Figure 22 Absorption changes of perovskite films during accelerated aging testing are depicted. Normalized absorbance changes at 700 nm wavelength of perovskite films with and without GSC during accelerated aging testing (3 suns intensity illumination; 80 °C).

[0067] Figure 23 PL mapping images of perovskite films after accelerated aging testing are depicted. PL mapping images of perovskite grains with (a) and without (b) GSC after 120 h accelerated aging testing (3 suns intensity illumination; 80 °C).

[0068] Figure 24 XRD intensity of perovskite films after accelerated aging testing is depicted. XRD patterns of perovskite films with (a) and without (b) GSC after 120 h accelerated aging testing (3 suns intensity illumination; 80 °C).

[0069] Figure 25 Humidity durability of PSCs with and without GSC is depicted. a, Schematic of the effect of TFSAP chemical functionalization on humidity resistance. b, Normalized absorbance at 760 nm wavelength of perovskite films with and without GSC placed in humidity conditions with 65-85 RH%. Inset are optical photographs of perovskite films after testing.

[0070] Figure 26 Simulated thermal conductivity of micro-heterointerfaces with and without GSC is depicted. Multilayer model was used to compare thermal conductivities with (a) and without (b) GSC, respectively. The height of perovskite and Sn02 layers is 500 nm, the thickness has been marked at the images. The nanogap shape induced by GSC was simplified as a rectangle with dimensions of 460 x 10 nm 2 Thermal conductivities k (c) with and without GSC are compared.

[0071] Figure 27 Model diagrams in FEA calculations are depicted. Cross-sectional model diagrams of grain-CTL microinterfaces with (a) and without (b) GSC were generated in FEA calculations. The nanogap induced by GSC was set as a crescent structure with a length of 460 nm and a depth of 10 nm at the heterointerface. Longitudinal and transversal guides are marked in both diagrams.

[0072] Figure 28 Evidence of GSC causing interfacial thermal build-up is shown. Temperature profiles guided by longitudinal (a) and transverse (b) lines at the bottom surface of perovskite grains with and without GSC. Figure 19

[0073] Figure 29 Temperature profiles of micro-heterointerfaces with external heat sources are shown. Temperature profiles of grain-CTL micro-heterointerfaces with (a) and without (b) GSC. The heat source was placed at the bottom surface of the Sn02layer. A temperature gradient was set from the bottom surface of the Sn02layer (85 °C) to the top surface of the grain (20 °C).

[0074] Figure 30 FEA simulation deformation and thermal stress of micro-heterointerfaces in extreme temperatures in thermal cycling are shown. 2D elastic deformation and thermal stress profiles of perovskite films with (a, c) and without (b, d) GSC in thermomechanical FEA results at -40 °C (a, b) and at 85 °C (c, d), respectively. Wireframe represents the device structure without deformation. The bottom surface of the ITO layer was set as a rigid boundary considering the restriction of deformation by the adjacent thick glass substrate. Micro-heterointerfaces show thermal stress build-up at the junctions where GSC exists.

[0075] Figure 31 The effect of the presence of GSC on interfacial adhesion strength is shown. Statistical distribution of normalized delamination area A d after delamination process of samples with P123, NTAC, and potassium trifluoromethanesulfonate (PTFS) based on a total of 24 measurements. Boxplot shows the mean, median, upper and lower minimum, 25-75% box limits, and 1.5 x interquartile range whiskers.

[0076] Figure 32 Two molecules with passivation functional groups are shown to fail to flatten GSC on perovskite bottom surface. a-b, Molecular structures of sodium dodecylbenzenesulfonate (SDBS) (a) and PTFS (b). c-d, AFM topography images of perovskite film bottom surface at perovskite-CTL heterointerface with addition of SDBS (c) and PTFS (d) to the precursor solution.

[0077] Figure 33 The mechanism by which flattening GSC enhances interfacial adhesion with I-SAM layer is shown to be beneficial. Schematic of interfacial adhesion of perovskite grains with (a) and without (b) GSC. I-SAM with -I end group can form hydrogen bonds with perovskite. The recessed central surface of grains with GSC cannot form hydrogen bonds due to the presence of nanogap at the micro-heterointerface. ​

[0078] Figure 34 Cross-sectional SEM images of perovskite films after thermal cycling test are shown. Cross-sectional SEM images of perovskite films with GSC (a) and without GSC (b) after thermal cycling test of 300 cycles (-40 °C to +85 °C).

[0079] Figure 35 Evidence showing that chemical passivation does not dominate light- current property improvement is shown. a, PL spectra of layered perovskite films (exposed buried surface) with GSC, with SDBS and with PTFS. b, PCE statistics of PSCs prepared with SDBS (n = 25) and PTFS (n = 25). Boxplot shows mean, median, upper and lower hinges, 25-75% box limits and 1.5 x interquartile range whiskers.

[0080] Figure 36 Evidence showing that GBG planarization does not dominate PCE and stability improvement is shown. AFM images of perovskite bottom surface (a) and statistical distribution of GBG side angle Θ (b) of perovskite films / devices with planarized GBG, J-V curves (c) and operation stability under MPP (d). The inset table in (c) shows extracted J-V parameters.

[0081] Figure 37 Effect of P123 with planarized GSC on device PCE is shown. PSCs prepared without P123 (original sample, n = 15) and with P123 (n = 15). PCE statistics of PSCs prepared with P123 (n = 15). Boxplot shows mean, median, upper and lower hinges, 25-75% box limits and 1.5 x interquartile range whiskers.

[0082] Figure 38 Temperature variation information during thermal cycling test is shown. Temperature variation curve of one cycle (54 min) during thermal cycling test.

[0083] Figure 39 Evidence showing that perovskite bottom surface and Sn02top surface have negligible spatial difference is shown. Statistical distribution R a values of each AFM image (corresponding position) of perovskite bottom surface (n = 10) and Sn02surface (n = 10). Boxplot shows mean, median, upper and lower hinges, 25-75% box limits and 1.5 x interquartile range whiskers.

[0084] Figure 40 Table 1 depicted shows contact angles of water (H20) and diiodomethane (CH2I2) on perovskite films with and without GSC.

[0085] ​Figure 41 Table 2 depicted shows the dispersive part (γ lv P ) and polar part (γ lv D ) of the surface tension of the two probing liquids H2O and CH2I2.

[0086] Figure 42 Table 3 depicted shows the thermal conductivity k, the constant volume heat capacity C P , the density p, the Young’s modulus M, the Poisson’s ratio v and the thermal expansion coefficient a in the thermo-mechanical FEA. DETAILED DESCRIPTION

[0087] Definitions

[0088] Throughout this disclosure, the word "comprise" or variations such as "comprises" or "comprising" will be understood to imply the inclusion of a stated whole or an integral part but not to the exclusion of any other whole or integral part. It will be further noted that the terms "comprise", "comprises", "comprising" and the like can mean "includes", "included", "including" and the like; and / or that the terms "consist", "consists", "consisting" and the like can mean "includes", "included", "including" and the like; and / or that the terms "consist essentially", "consists essentially", "consisting essentially" and the like can include elements or steps not expressly recited, but which are essentially or otherwise implicitly included in such making or using.

[0089] Further, throughout this disclosure, the word "include" or variations such as "includes" or "including" will be understood to imply the inclusion of a stated whole or an integral part but not to the exclusion of any other whole or integral part.

[0090] Unless otherwise expressly stated, terms in the disclosure that are not quantified include both the singular and the plural. Additionally, the disclosure also includes the specific numerical value itself if the use of the term "about" precedes the numerical value, unless otherwise specifically stated. As used herein, unless otherwise stated or inferred, the term "about" means a variation of ±10%, ±7%, ±5%, ±3%, ±1% or ±0% of the nominal value.

[0091] As used herein, the terms "weight percent," "wt-%," "percent by weight," "wt.%" and variations thereof refer to the concentration of a substance as the weight of that substance divided by the total weight of the composition and multiplied by 100. It is understood that, as used herein, "percent," "%," and the like are intended to be synonymous with "weight percent," "wt-%," etc.

[0092] The methods and compositions of the present disclosure can comprise, consist essentially of, or consist of the components and ingredients of the present disclosure, as well as other ingredients described herein. As used herein, "consisting essentially of" means that the methods and compositions can include additional steps, components or ingredients, but only if the additional steps, components or ingredients do not materially alter the basic and novel characteristics of the claimed methods and compositions.

[0093] The term "one or more perovskite solar cells" used herein refers to solar cells that use a perovskite structured material as a light absorbing layer. When light is incident on the perovskite material, it excites electrons in the material, creating electron-hole pairs. Perovskite materials have excellent charge transport properties, allowing the electrons and holes to separate and transport to the electrodes, where they can be collected as an electric current.

[0094] A perovskite solar cell of the formal structure typically consists of a transparent conductive oxide (TCO) layer, a hole transport layer (HTL), a perovskite light absorbing layer, an electron transport layer (ETL), and a metal electrode. In a perovskite solar cell with an inverse structure, the order of the layers is reversed compared to the formal structure, with the ETL layer, perovskite layer, HTL, and metal electrode in that order adjacent to the TCO layer.

[0095] Existing perovskite compound films in PSCs are polycrystalline, consisting of densely packed individual crystalline grains. As such, the heterointerface of the perovskite compound film with the charge transport layer (CTL) can be viewed as a collection of crystalline grain-CTL micro-heterointerface segments. The properties of each segment of the crystalline grain-CTL micro-heterointerface cumulatively determine the properties of the overall heterointerface between the perovskite compound film and the CTL layer in a PSC. It is therefore crucial to ensure a high degree of microstructural integrity of the individual crystalline grain-CTL micro-heterointerface in order to form a more ideal perovskite heterointerface.

[0096] The inventors have used atomic force microscopy and depth profiling to reveal the ubiquitous presence of grain surface concavities (GSCs) on the surface of individual grains of representative perovskite compound films, a microstructure that has not been adequately explored in the field. These GSCs inevitably lead to buried nanoscale gaps between the grain center and the underlying CTL. Due to their relatively small depth (compared to the size of individual grains and the height of grain boundary grooves (GBGs)), it is not surprising that GSCs have been overlooked in the morphological and microstructural studies of PSCs in the past few years.

[0097] It has been found that the formation of these GSCs is attributed to solid-state ionic plastic flow from the GBG and the grain surface center to the ridges, induced by the thermal-driven grain boundary (GB) grooves and the biaxial tensile strain (BTS) induced by grain coalescence, respectively. More importantly, GSCs impart significant negative impacts on the carrier extraction, chemical, and thermomechanical properties of perovskite heterointerfaces. Due to the layer-by-layer processing of PSCs, any negative impacts on the structural and functional integrity of the perovskite top surface side can be compensated by the conformal deposition of successive layers.

[0098] Accordingly, the present study focuses on the buried bottom perovskite heterointerfaces. To mitigate the negative impacts of GSCs, certain surfactants can be added to control the interfacial energy of the grain surface and GBs to simultaneously suppress GB grooves and BTS. Thus, perovskite films are produced in which minimal GSCs are observed on the individual grain bottom surface, resulting in robust and stable grain-CTL microheterointerfaces. PSCs incorporating this microstructural engineering achieve a high power conversion efficiency (PCE) of 25.5%. The PCE of PSCs after GSC removal can be retained at 83%, 90%, and 90% in device stability tests following the international consensus protocols ISOS-T-3 (300 cycles), ISOS-D-3 (660 h), and ISOS-L-11 (1290 h), demonstrating the advantages of GSC engineering.

[0099] The present disclosure provides a perovskite layer comprising a perovskite compound and a surfactant, wherein the perovskite compound is represented by Formula 1:

[0100] (A + ) 1-y (A’ + ) y (M 2+ )(X - )3 1

[0102] wherein y is 0.01-0.99;

[0103] M 2+ is Pb 2+ , Sn2+ or Ge 2+ ;

[0104] A + and A' + each independently is Cs + , Rb + , CH3NH3 + , CH3CH2NH3 + , H(C=NH2)NH2 + or Me(C=NH2)NH2 + ; and

[0105] X - is independently in each occurrence F - , Cl - , Br - or I - , wherein A + and A' + are the same or different; and

[0106] The surfactant comprises a sulfonate surfactant, an alcohol alkoxylate surfactant, a quaternary ammonium surfactant, or a mixture thereof.

[0107] In certain embodiments, the sulfonate surfactant comprises a sulfonate group substituted with a perhalogenated C4-C 12 alkyl group. In certain embodiments, the sulfonate surfactant comprises a sulfonate group substituted with a perhalogenated C4-C 10 alkyl group or a perhalogenated C4-C8alkyl group. In certain embodiments, the perhalogenated C4-C 12 alkyl group is a linear or branched, unsubstituted or substituted, saturated or unsaturated alkyl group. In certain embodiments, the sulfonate surfactant comprises a sulfonate group substituted with a perhalogenated n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, or n-dodecyl substituent.

[0108] In certain embodiments, the sulfonate surfactant is a fluorocarbon-based surfactant. In certain embodiments, the sulfonate surfactant is a perfluoroalkyl sulfonate. In certain embodiments, the perfluoroalkyl sulfonate is a perfluorohexane sulfonate, a perfluorobutane sulfonate, a perfluorodecane sulfonate, or a mixture thereof.

[0109] In certain embodiments, the quaternary ammonium surfactant comprises one or more C1-C 16 alkyl substituents. In certain embodiments, the quaternary ammonium surfactant comprises one or more C4-C 12 alkyl substituents, or one or more C6-C 10 alkyl substituents. In certain embodiments, the C1-C16 Alkyl is a straight chain or branched, unsubstituted or substituted, saturated or unsaturated alkyl group. In certain embodiments, the quaternary ammonium surfactant comprises a methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, n-pentyl, iso-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, or n-dodecyl substituent.

[0110] In certain embodiments, the surfactant comprises one or more of: potassium perfluorohexane-1 -sulfonate (TFSAP), sodium perfluorohexane-1 -sulfonate, potassium perfluorobutane-1 -sulfonate, sodium perfluorobutane-1 -sulfonate, potassium perfluorodecane-1 -sulfonate, sodium perfluorodecane-1 -sulfonate, poly(ethylene oxide) / poly(propylene oxide) (EO / PO) block copolymer, or N,N,N-trimethyloctyl-1 -ammonium chloride.

[0111] In certain embodiments, M 2+ is Pb 2+ ; and A + and A’ + each independently is Cs + , CH3NH3 + , or H(C=NH2)NH2 + .

[0112] In certain embodiments, the perovskite layer comprises a perovskite of formula 2: + 1-y (Cs + ) y (Pb 2+ )(I - )3, where y is 0.01-0.99.

[0113] In certain embodiments, the perovskite layer comprises a perovskite of formula 2:

[0114] [(A + ) 1-y (A’ + ) y (M 2+ )(X - )3] 1-z [(A” + )(M’ 2+ )(Q - )3] z 2

[0116] where y is 0.01-0.99;

[0117] z is 0.01-0.99;

[0118] M 2+ ​is Pb 2+ , Sn 2+ or Ge 2+ ;

[0119] M' 2+ is Pb 2+ , Sn 2+ or Ge 2+ ;

[0120] A + , A' + and A" + each independently is Cs + , Rb + , CH3NH3 + , CH3CH2NH3 + , H(C=NH2)NH2 + or Me(C=NH2)NH2 + ; and

[0121] X - and Q - are independently in each case F - , Cl - , Br - or I - , wherein A + and A' + are identical or different.

[0122] In certain embodiments, each of M 2+ and M' 2+ is Pb 2+ ; each of A + and A' + is independently Cs + , CH3NH3 + or H(C=NH2)NH2 + ; and A" + is CH3NH3 + .

[0123] In certain embodiments, the perovskite layer comprises [(H(C=NH2)NH2 + ) 1-y (Cs + ) y (Pb 2+ )(I - )3] 1-z [(CH3NH3 + )(Pb 2+ )(Br - )3] z , wherein y is 0.01-0.99 and z is 0.01-0.99.

[0124] In Formula 1 and Formula 2, y is 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, or 0.99. In Formula 1 and Formula 2, z is 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, or 0.99.

[0125] In certain embodiments, the perovskite compound film comprises FA 0.9 Cs 0.1 PbI3, (FA 0.95 Cs 0.05 PbI3) 0.975 (MAPbBr3) 0.025 , FAPbI3, Cs 0.05 FA 0.95 PbI3, Cs 0.17 FA 0.83 PbI3, Cs 0.05 FA 0.85 MA 0.1 PbI3, Cs 0.05 FA 0.81 MA 0.14 PbI 2.55 Br 0.45 , Cs 0.05 (FA 0.95 MA 0.05 ) 0.95 Pb(I 2.95 Br 0.05 )3 or any mixture thereof.

[0126] In certain embodiments, the perovskite layer comprises a plurality of perovskite grains, and a bottom surface of each of the plurality of perovskite grains comprises a single grain surface concave (GSC) and a ridge surrounding the GSC, and wherein an average angle ξ between a line connecting a ridge apex and a GSC center and a top surface opposite the bottom surface of the grain is 0°-1.5°.

[0127] The geometric parameter ξ is proposed by the inventors to evaluate the microstructure of perovskite compound grains to roughly state the degree of curvature with respect to an ideal flat surface.

[0128] In the present disclosure, for a perovskite solar cell with a formal structure, the bottom surface of a perovskite grain is the surface in contact with the electron transport layer, or for a perovskite solar cell with an inverted structure, the bottom surface of a perovskite grain is the surface in contact with the hole transport layer.

[0129] In certain embodiments, the perovskite grains have an average angle ξ of 0° to 1°, or 0° to 0.5°. In certain embodiments, the perovskite grains have an angle ξ of 0°, 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, 1.0°, 1.1°, 1.2°, 1.3°, 1.4°, or 1.5° or a range of any values therebetween.

[0130] In the present disclosure, the perovskite grains in the provided perovskite layer have a nearly flat surface, which is advantageous to ensure the continuity and flatness of the heterointerface between the perovskite compound film and the charge transport layer (CTL), and form a more ideal heterointerface.

[0131] In addition to the geometric parameter ξ, another geometric parameter θ is used to further evaluate the microstructure of the perovskite compound grains. In certain embodiments, the perovskite layer comprises a plurality of perovskite grains and a grain boundary groove (GBG) between the bottom surfaces of each adjacent perovskite grain, the GBG is surrounded by the edges of the adjacent perovskite grains as GBG side walls, and the average angle θ between the tangent of the GBG side wall and the top surface opposite the grain bottom surface is 0°-15°.

[0132] In certain embodiments, the perovskite grains have an average angle θ of 0° to 12°, or 0° to 10°. In certain embodiments, the grains in the perovskite compound film have an angle θ of 0°, 0.5°, 1.0°, 1.5°, 2.0°, 2.5°, 3.0°, 3.5°, 4.0°, 4.5°, 5.0°, 5.5°, 6.0°, 6.5°, 7.0°, 7.5°, 8.0°, 8.5°, 9.0°, 9.5°, 10.0°, 10.5°, 11.0°, 11.5°, 12.0°, 12.5°, 13.0°, 13.5°, 14.0°, 14.5°, or 15.0° or a range of any values therebetween.

[0133] Depending on the process and conditions used to produce the perovskite layer, the perovskite particles can form a single layer or a multi-layer structure. For example, through a slot-die coating process and by tuning the specific precursor solution, a single layer structure, perovskite compound film with large size grains, can be prepared. Single layer structure is more suitable for reducing grain boundary defects, optimizing carrier transport pathways, especially in large area manufacturing. The formation of multi-layer structure is closely related to the crystallization kinetics, stability of precursor solution, and solvent evaporation rate during the preparation process. For example, the inconsistency of crystallization rate between the upper and lower layers can cause the grains to stack into multiple layers. Multi-layer structure can also improve efficiency by optimizing the combination of different band gap perovskite layers.

[0134] In certain embodiments, the perovskite grains form a single layer in the perovskite compound film. In certain embodiments, the perovskite grains form a multi-layer in the perovskite compound film.

[0135] In certain embodiments, the perovskite grains have an average size in the range of 50-900 nm, 100-500 nm, or 300-500 nm. In certain embodiments, the perovskite compound grains have a size of 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, or a range having any of these values as endpoints.

[0136] The present disclosure also provides a method for producing a perovskite layer, the method comprising:

[0137] providing a perovskite precursor solution, the precursor solution comprising one or more metal salts each independently represented by the formula MX2, two or more salts each independently represented by the formula AZ, a surfactant, and a solvent, wherein M is Pb 2+ , Sn 2+ , or Ge 2+ , A is Cs + , Rb + , CH3NH3 + , CH3CH2NH3 + , H(C=NH2)NH2 + , or Me(C=NH2)NH2 + , X is independently at each occurrence F - , Cl - , Br - , or I - , and Z is independently at each occurrence F - , Cl - , Br -or I - ;

[0138] depositing the perovskite precursor solution on a surface of a charge transport layer to form a wet film; and

[0139] annealing the wet film to form the perovskite layer.

[0140] The perovskite precursor solution can be deposited by, for example, spin coating, doctor blading, spray coating, slot-die coating, inkjet printing, and vapor deposition. In certain embodiments, the perovskite precursor solution is deposited by spin coating.

[0141] In certain embodiments, the solvent used herein can comprise an organic solvent such as dimethylformamide (DMF), dimethylsulfoxide (DMSO), gamma-butyrolactone (GBL), N-methyl-2-pyrrolidone (NMP), acetonitrile (ACN), chlorobenzene (CB), anisole, N,N'-dimethylpropyleneurea (DMPU), toluene, ethanol, methanol, or a mixture thereof.

[0142] The selection and combination of these solvents can be optimized according to the specific perovskite composition and fabrication process to achieve the best film quality and device performance. In certain embodiments, the solvent used herein is DMF, DMSO, or a mixture thereof.

[0143] In certain embodiments, the method can optionally include treating the wet film with an anti-solvent or other additives to control the morphology and grain size of the film and enhance the stability of the film. The anti-solvent can comprise chlorobenzene, toluene, diethyl ether (DE), ethyl acetate (EA), isopropyl alcohol (IPA), anisole, t-butanol, or a mixture thereof.

[0144] Annealing the perovskite wet film can significantly affect the film quality and device performance. The optimal annealing conditions can vary depending on the specific perovskite composition and desired film properties. In certain embodiments, the wet film is annealed at a temperature of 100°C-200°C or 100°C-180°C. In certain embodiments, the wet film is annealed at a temperature of 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 200°C, or a range of any values in between.

[0145] In certain embodiments, the wet film is annealed for a period of 5-60 min or 5-40 min. In certain embodiments, the wet film is annealed for a period of 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or a range of any values in between.

[0146] In certain embodiments, the perovskite precursor solution comprises (Cs + )(I - ), (H(C=NH2)NH2 + )(I - ), (Pb 2+ )(I - )2, and sodium perfluorohexane-1-sulfonate.

[0147] In certain embodiments, the perovskite precursor solution comprises (Cs + )(I - ), (H(C=NH2)NH2 + )(I - ), (CH3NH3 + )(CI - ), (Pb 2+ )(I - )2, (CH3NH3 + )(Pb 2+ )(Br - )3, and sodium perfluorohexane-1-sulfonate.

[0148] In certain embodiments, the surfactant has a concentration of 0.1-5 mg / ml in the perovskite precursor solution. In certain embodiments, the surfactant has a concentration in the perovskite precursor solution of 0.1 mg / ml, 0.2 mg / ml, 0.3 mg / ml, 0.4 mg / ml, 0.5 mg / ml, 0.6 mg / ml, 0.7 mg / ml, 0.8 mg / ml, 0.9 mg / ml, 1.0 mg / ml, 1.1 mg / ml, 1.2 mg / ml, 1.3 mg / ml, 1.4 mg / ml, 1.5 mg / ml, 1.6 mg / ml, 1.7 mg / ml, 1.8 mg / ml, 1.9 mg / ml, 2.0 mg / ml, 2.1 mg / ml, 2.2 mg / ml, 2.3 mg / ml, 2.4 mg / ml, 2.5 mg / ml, 2.6 mg / ml, 2.7 mg / ml, 2.8 mg / ml, 2.9 mg / ml, 3.0 mg / ml, 3.1 mg / ml, 3.2 mg / ml, 3.3 mg / ml, 3.4 mg / ml, 3.5 mg / ml, 3.6 mg / ml, 3.7 mg / ml, 3.8 mg / ml, 3.9 mg / ml, 4.0 mg / ml, 4.1 mg / ml, 4.2 mg / ml, 4.3 mg / ml, 4.4 mg / ml, 4.5 mg / ml, 4.6 mg / ml, 4.7 mg / ml, 4.8 mg / ml, 4.9 mg / ml, or 5 mg / ml, or any range derivable therein.

[0149] In certain embodiments, the one or more metal salts each independently represented by the formula MX2has a concentration of 0.5-2.0 M in the perovskite precursor solution. In certain embodiments, the one or more metal salts each independently represented by the formula MX2has a concentration of 0.5 M, 0.6 M, 0.7 M, 0.8 M, 0.9 M, 1.0 M, 1.1 M, 1.2 M, 1.3 M, 1.4 M, 1.5 M, 1.6 M, 1.7 M, 1.8 M, 1.9 M, 2.0 M, or a range of any values therebetween in the perovskite precursor solution.

[0150] In certain embodiments, the two or more salts each independently represented by the formula AZ has a concentration of 0.5-2.0 M in the perovskite precursor solution. In certain embodiments, the two or more salts each independently represented by the formula AZ has a concentration of 0.5 M, 0.6 M, 0.7 M, 0.8 M, 0.9 M, 1.0 M, 1.1 M, 1.2 M, 1.3 M, 1.4 M, 1.5 M, 1.6 M, 1.7 M, 1.8 M, 1.9 M, 2.0 M, or a range of any values therebetween.

[0151] In certain embodiments, the method for producing a perovskite layer comprises:

[0152] dissolving (Cs + )(I - ), (H(C=NH2)NH2 + )(I - ), and (Pb 2+ )(I - )2 together with TFSAP in a solvent comprising DMF and DMSO to make a perovskite precursor solution;

[0153] depositing the perovskite precursor solution on an ETL surface on a substrate to form a wet film;

[0154] adding an anti-solvent to the wet film; and

[0155] annealing the wet film at a temperature of 150 °C - 180 °C for 5 - 15 min.

[0156] In certain embodiments, the method for producing a perovskite layer comprises:

[0157] dissolving (Cs + )(I - ), (H(C=NH2)NH2 + )(I - ), (CH3NH3 + )(Cl - ), (Pb 2+ )(I -)2, (CH3NH3 + )(Pb 2+ )(Br - )3 is dissolved in a mixed solvent comprising DMF and DMSO along with TFSAP to make a perovskite precursor solution;

[0158] The perovskite precursor solution is deposited on the surface of the ETL on the substrate to form a wet film;

[0159] An anti-solvent is added to the wet film; and

[0160] The wet film is annealed at a temperature of 100-120 °C for 30-40 min.

[0161] The present disclosure further provides a photovoltaic device comprising the perovskite compound film as described above. The photovoltaic device comprises a perovskite solar cell (PSC), a perovskite light emitting diode, a perovskite laser, and a perovskite photodetector.

[0162] The addition of a specific surfactant to the perovskite film enables the photovoltaic device comprising the perovskite compound film of the present disclosure to have an improved power conversion efficiency (PCE). In particular, for a perovskite solar cell (PSC), the power conversion efficiency can be improved to a maximum of 23.5-25.5%.

[0163] In certain embodiments, the perovskite solar cell can have a formal structure comprising a transparent or semi-transparent conductive substrate, an electron transport layer, the perovskite compound film as described above, a hole transport layer, and a metal electrode deposited in that order. In certain embodiments, the perovskite solar cell can have an inverted structure comprising a transparent or semi-transparent conductive substrate, a hole transport layer, the perovskite compound film as described above, an electron transport layer, and a metal electrode deposited in that order.

[0164] The transparent or semi-transparent conductive substrate can be previously cleaned in a solvent (e.g., isopropyl alcohol, acetone, and water) by ultrasonic cleaning. The substrate can also be treated with UV light to achieve surface activation.

[0165] The transparent conductive oxide in the conductive substrate is selected from the group consisting of indium tin oxide (ITO), zinc oxide, doped tin oxide, and doped zinc oxide, such as fluorine-doped tin oxide (FTO) or aluminum-doped tin oxide (AZO), and the like.

[0166] In certain embodiments, the transparent conductive oxide can comprise 90 wt% to 100 wt% of ITO, FTO, or AZO. In certain embodiments, the transparent conductive oxide can consist essentially of ITO, FTO, or AZO. In certain embodiments, the transparent conductive oxide is ITO.

[0167] In certain embodiments, the perovskite compound film has a thickness of 100 nm to 1000 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm.

[0168] The materials used to form the electron transport layer and the hole transport layer can be materials commonly used in perovskite solar cells. In certain embodiments, the electron transport layer can be formed from a material selected from the group consisting of titanium dioxide (Ti02), tin oxide (Sn02), zinc oxide (ZnO), zinc tin oxide (Zn2Sn04), [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), perylene diimide (PDI). In certain embodiments, the hole transport layer can be formed from a material selected from the group consisting of 2,2',7,7'-tetrakis(N,N-dip-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD), poly(triarylamine) (PTAA), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), poly(3-hexylthiophene-2,5-diyl) (P3HT), nickel oxide (Ni02), copper(I) thiocyanate (CuSCN), 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene), and copper phthalocyanine (CuPc). 61 x

[0169] In certain embodiments, the perovskite solar cell comprises an interfacial glue layer between the perovskite compound film and the charge transport layer (electron transport layer or hole transport layer). The interfacial glue can be selected from the group consisting of (3-iodopropyl)trimethoxysilane (Si(OCH3)3(CH2)3I), potassium tetrafluoroborate (KBF4), trifluoromethanesulfonamide (CF3SO2NH2), aminopropyltriethoxysilane (H2NCH2CH2CH2Si(OC2H5)3), polyhexamethylene guanidinium hydrochloride, and 5,6-isopropyridine-L-ascorbic acid.

[0170] Examples

[0171] Materials and Methods

[0172] 1. Raw materials.

[0173] ​​Tin(IV) oxide (15 wt.%, in a colloidal dispersion in H2O) was purchased from Alfa Aesar (USA). PbI2(99.99%), (3-iodopropyl)trimethoxysilane (Si(OCH3)3(CH2)3I, 95%), and 4-isopropyl-4'-methyl diphenyliodonium tetra(pentafluorophenyl)borate (TPFB, >98%) were all purchased from TCI (Japan). HC(NH2)2I (FAI, >99.99%), methylammonium chloride (MACI, >99.99%), 4-methoxy-phenethylammonium iodide (MeO-PEAI, >99.99%), and FK 209 Co(III) TFSI salt were all purchased from Greatcell Solar (Australia). CsI (99.999%) and PTAA were both purchased from Xi’an Yuri Solar (China). Spiro-OMeTAD (99.8%) was purchased from Borun Chemical (China). Potassium perfluorohexane-1 -sulfonate (TFSAP, 95%) was purchased from Macklin (China). Potassium chloride (KCI, 99.0-100.5%), poly(methyl methacrylate) (PMMA), 4-tert-butylpyridine (t-bp, 96%), lithium bis(trifluoromethanesulfonyl)imide salt (99.95%), PbBr2(≥99%), dimethyl sulfoxide (DMSO, 99.9%), dimethylformamide (DMF, 99.8%), chlorobenzene (CB, 99.8%), toluene (TB, 99.8%), acetonitrile (ACN, >99.9%), diethyl ether (DE, 99%), and isopropyl alcohol (IPA, 99.5%) were all purchased from Merck (USA). Dichloromethane was purchased from International Laboratory USA.

[0174] 2. Device fabrication.

[0175] 2-1. Fabrication of a basic device with a pristine perovskite film

[0176] The pre-patterned ITO substrates were cleaned by ultrasonication in each of deionized water, acetone and isopropanol for 15 min. All substrates were cleaned by UV / ozone treatment for 30 min after drying by N2gas flow. The Sn02colloidal precursor was diluted with deionized water (v / v 1 :5) and spin-coated on the ITO substrates at 3000 rpm for 30 s, followed by annealing at 180 °C for 30 min. The prepared Sn02film was treated by UV / ozone for 10 min before subsequent deposition. The KCl solution (3 mg / mL in DI water) was spin-coated on the Sn02layer at 4000 rpm for 20 s, followed by annealing at 100 °C for 10 min.

[0177] The perovskite layer was formed from a FA-Cs compound FA 0.9 Cs 0.1 PbI3or (FA 0.95 Cs 0.05 PbI3) 0.975 (MAPbBr3) 0.025 was formed, which can be used in different devices. The steps for preparing the perovskite layer are described as follows:

[0178] FA 0.9 Cs 0.1 PbI3perovskite layer (original film 1). The perovskite precursor solution was prepared by dissolving 36 mg of Csl, 154.7 mg of FAI and 461 mg of Pbl2in 1 mL of mixed DMF-DMSO solvent (v / v 7:3). The precursor solution was stirred at room temperature overnight and then used after filtration. 50 pL of the precursor solution was dropped onto the surface of the Sn02ETL prepared above. The spin-coating process was carried out in three steps: 500 rpm for 5 s, 3000 rpm for 10 s, and finally 5000 rpm for 30 s. At the last step, 400 pL of toluene was dropped onto the substrate within 1 s within 10 s. The deposited film was immediately annealed on a hotplate at 170 °C for 6 min. This original film 1 was used for basic research.

[0179] (FA 0.95 Cs 0.05 PbI3) 0.975 (MAPbBr3) 0.025Preparation of perovskite layer (original film 2). Perovskite precursor solution was prepared by dissolving 228.8 mg FAI, 18.2 mg CsI, 33.7 mg MACI, 705.3 mg PbI2 and 18.2 mg MAPbBr3 single crystal in 1 mL mixed DMF-DMSO (v / v 8: 1). MAPbBr3 single crystal was synthesized by mixing MABr and PbBr2 in 1:1 molar ratio with a concentration of 0.2 M in DMF solvent and the single crystal was trapped with dichloromethane anti-solvent. Then 60 μL of precursor solution was dropped onto the SnO2 layer, followed by a two-stage spin-coating process (spun at 1000 rpm for 10 s, and at 4000 rpm for 30 s). Within 15 s of the second step, 800 μL of diethyl ether was dropped onto the rotating perovskite surface within 2 s. The wet film was annealed on a hotplate at 100 °C for 40 min. After the film was cooled to room temperature, 50 μL of MeO-PEAI (dissolved in IPA; 4 mg / ml) passivation layer was spin-coated on the perovskite layer at 5000 rpm for 30 s, followed by annealing at 100 °C for 5 min to improve the overall V OC The original film 2 was used for performance study of devices with high PCE.

[0180] HTL solution was prepared by mixing 1 mL of Spiro-OMeTAD solution (91 mg / mL in chlorobenzene) with 36 μL of 4-tert-butylpyridine, 21 μL of Li-TFSI solution (520 mg / mL in acetonitrile) and 16 μL of FK209 solution (375 mg / mL in acetonitrile). Then 50 μL of HTL solution was spin-coated onto the perovskite layer at 3000 rpm for 30 s. The Spiro-OMeTAD layer was placed in a drying cabinet (humidity less than 5%) for 2 days to facilitate the oxidation process of Spiro-OMeTAD. For stability test, PTAA was used instead of Spiro-OMeTAD. Here 50 μL of PTAA solution (30 mg / ml in CB with 3 mg / ml TPFB doping) was spin-coated onto the perovskite layer at 2000 rpm for 30 s. Finally, 80 nm Au was deposited by thermal evaporation. For device encapsulation, we applied UV glue on the edge of the device, followed by a typical curing process.

[0181] 2-2. Fabrication of devices with target perovskite film

[0182] Fabrication of devices was the same as that of the base device, except that the perovskite film was modified with the surfactant of TFSAP.

[0183] Perovskite films (target films) modified with surfactant of TFSAP were prepared as follows. In one embodiment, a TFSAP stock solution was prepared in mixed DMF-DMSO solvent and added to a perovskite precursor solution containing FA 0.9 Cs 0.1 PbI3 0.95 Cs 0.05 PbI3) 0.975 (MAPbBr3) 0.025 In another embodiment, a TFSAP stock solution was prepared in mixed DMF-DMSO solvent and added to a perovskite precursor solution containing (FA

[0184] 3. Material and device characterization methods.

[0185] AFM topography images of perovskite layers were acquired using Multimode 8 (Bruker, USA) with RTESP-300 tip in non-contact tapping mode. Scanning electron microscope (Gemini 1530, LEO, Zeiss, Germany) was used to characterize top view surface and cross-sectional SEM images. XRD (D8 Advance, Bruker, USA) with Cu Ka radiation was used to characterize the crystal structure of perovskite layers. Steady-state PL and TRPL signals were directed into a spectrometer (Ando Kymera 328i) excited with a 375 nm picosecond laser (LDH-D-C-375, PicoQuant, Germany). PL signals were further collected by an electron multiplying charge-coupled device (EMCCD; Andor iXon Life 888, Oxford Instruments, UK) for steady-state PL and single-photon avalanche photodiode for TRPL measurements. In order to measure PL from the bottom side of fabricated perovskite films, quartz was used instead of ITO glass substrate to minimize light scattering. PL mapping images were captured by a digital microscope camera (Nikon DS-Qi2) with UV light source (250-450 nm) and filter (long pass after 726 nm). UV-visible spectra were acquired by a commercial UV-visible spectrophotometer (Cary 300, Agilent, USA).

[0186] Source table (2612, Keithley, USA) in AM 1.5G spectrum (one solar illumination; 100mW cm⁻¹) -2 JV characteristics of perovskite devices were measured using an AM 1.5G spectrum generated by a solar simulator (Sirius-SS, Zolix, Beijing, China) in a nitrogen-filled glove box. All devices were measured with reverse scans (from 1.3V to -0.02V) in 0.02V steps and with a delay of 10ms. The effective area defined by the shadow mask was 0.05cm². 2 The light intensity was certified by NIST according to ISO-17025 standards. Calibration was performed using a reference solar cell. External quantum efficiency spectra were recorded in AC mode at a chopping frequency of 165 Hz on a solar cell quantum efficiency measurement system (QE-R3011, Enlitech, China). For MPP tracking testing of the PSC devices, following the ISOS-L-11 protocol, the devices were placed in a test chamber within a nitrogen glove box with continuous flow of N2 gas to maintain the test chamber temperature at 40–50 °C. These devices were operated at maximum power point bias, and data points were collected periodically. For thermal cycling stability testing (ISOS-T-3 protocol), the packaged devices were placed in an environmental chamber controlled by a custom program. The temperature was set to cycle between -40 °C and +85 °C for 54 min per cycle. The temperature change curve for one cycle (54 min) during the thermal cycling test is shown below. Figure 38 Humidity is controlled below 20% RH. PCE testing of the device is performed at room temperature in a nitrogen glove box. For damp heat stability testing (ISOS-D-3 protocol), the packaged device is placed in an environmental chamber with a temperature of 85°C and a humidity of 85% RH. PCE testing of the device is also performed at room temperature in a nitrogen glove box.

[0187] For the measurement process of GBG and GSC side angles, in sample preparation, epoxy resin was applied to a PMMA-protected perovskite layer, and then the film was covered with a glass slide. Next, the samples were stored in a dark, dry chamber (RH < 15%) until the epoxy resin was fully cured and reached its maximum bond strength. The corresponding locations were deliberately marked (using a glass cutter to pre-mark a grid on the back of the glass substrate to mark the SnO2 region) to ensure that the detected SnO2 top surface and perovskite bottom surface originated from the relevant areas. Similarly, a relatively smaller grid was pre-marked on the back of the coverslip to mark the perovskite region. Figure 39It is shown that the spatial difference of AFM morphology in the corresponding locations is negligible. Next, force is applied to delaminate the perovskite layer from the Sn02 ETL. This method can effectively separate the perovskite bottom surface from the Sn02 surface without degrading the perovskite film (in areas with sufficient area). Next, high-resolution AFM scans are performed on the Sn02 top surface and the perovskite bottom surface to obtain 2D height profiles. AFM height images are analyzed using NanoScope Analysis software (V1.8). The profiles of grain boundary trenches and intra-grain height are extracted from these images. For the standard perovskite film delamination test, samples with the structure ITO / Sn02 / perovskite / PMMA are first fabricated. The Sn02 and perovskite layers are prepared following the method of PSC devices. Then a PMMA solution (10 mg / mL in CB) is spin-coated on the perovskite surface at 3000 rpm for 30 seconds, and the sample is placed in a nitrogen glovebox until the solvent is completely evaporated. The PMMA layer is used to prevent the reaction between the epoxy and the perovskite layer. A blade array with 1 mm spacing is used to scribe the sample surface to create a standard grid. A thin layer (2 pm) of epoxy resin film is coated to adhere the glass substrate to the film structure, which is kept in a dry air glovebox (<15% RH) for complete epoxy curing. The area ratio of delamination is calculated by comparing the number of perovskite grids peeled off on the glass substrate with the total number of grids covered by the epoxy. The interfacial adhesion rating is based on the ASTM D3359 standard. 0B represents an area greater than 65% removed from the substrate, corresponding to the worst interfacial strength. 1B, 2B, 3B, and 4B represent removal areas of 35-65%, 15-25%, 5-15%, and less than 5%, respectively. 5B represents no remaining area on the substrate after delamination, corresponding to the strongest interfacial strength. For each GB and grain microsurface, two measurements are taken at different locations on it to ensure the accuracy of Θ and ξ.

[0188] For the heat transport measurements, IPVP TA experiments were performed on samples with a glass / ITO / Sn02 / perovskite / PMMA structure. In the IPVP TA experiments, mid-infrared (MIR) pump pulses were generated by a high-energy MIR optical parametric amplifier (OPA; Orpheus-One-HE, Light Conversion). The OPA was powered by a Pharos amplifier with a 170 fs pulse duration, 1030 nm wavelength, and 2 kHz repetition rate, and was reduced to 1 kHz by an optical chopper. Broadband probe pulses at 2 kHz repetition rate were generated by a supercontinuum spectral laser (DISCO-2-UV, Leukos), which was electronically triggered and delayed by a fs pump laser with a digital delay generator (DG645, Stanford Research Systems). The transmitted probe light was captured by a high-speed USB spectrometer (AvaSpec-ULS2048CL-EVO, Avantes). The perovskite layer and the PMMA layer were maintained at a thickness of about 100 nm and 30 nm, respectively. The sample was vibrationally excited by MIR pulses centered at 3170 nm (in resonance with N-H and C-H stretching modes), and the pump-induced lattice temperature rise resulted in a change in transmittance, which was captured by the time-delayed broadband visible probe. Here, dT / T represents the differential change in transmittance and is defined as dT / T = (T(t) - T(0)) / T(0), where T(t) is the transmittance at a delay time t after pump excitation, and T(0) is the transmittance before pump excitation.

[0189] GaussAmp function was used to fit Figure 1 j and Figure 36 the curves on the histograms. Normal distribution curves were used to fit Figure 4c the histograms in

[0190] Characterization

[0191] Geometrical features and chemical adaptation of GSC

[0192] Two formamidinium-cerium (FA-Cs) perovskite film samples (FA 0.9 Cs 0.1 PbI3composition) with an ITO / Sn02 / perovskite structure were intentionally prepared. One sample (original film 1) was prepared from a perovskite solution without additives, while the other (target film 1) was prepared from a perovskite solution with TFSAP (an anionic surfactant) added. The unique molecular properties of TFSAP enable it to regulate the microstructural evolution and produce perovskite grains with minimal GSC on the bottom surface, as will be explained in detail later.

[0193] After the membrane is manufactured, it is used. Figure 5 The method shown mechanically separates the perovskite layer from the SnO2 electron transport layer (ETL). High-resolution atomic force microscopy (AFM) is then used to characterize the flipped perovskite film substrate surface, enabling quantitative analysis of the geometric features of the grain surface microstructure originally located at the perovskite-ETL heterostructure interface. Figure 1 In Figures a and b, AFM morphologies of perovskite surfaces with and without gas-cell structures (GSCs) are presented, respectively. For the pristine perovskite film, a polycrystalline microstructure is observed, with high-contrast GBGs forming between crowded individual grains, and GSCs appearing on most grains. The GSC microstructure can be distinguished by the following: in the conventional film, the edge regions within a specific grain are higher than the central regions. In contrast, GSCs are rarely observed on the grain microsurfaces of the target film. Figure 1 As shown, grains (c, e) contain microsurfaces with recessed centers surrounded by adjacent ridges and GBGs, while grains (d, f) contain nearly flat microsurfaces. This is illustrated by a narrow slice of AFM 2D / 3D image showing a typical full grain and adjacent GBs. Figure 1 (cf) Comparison of their detailed and local geometric features. For the original film 1, the grains consist of a recessed central surface surrounded by ridges and GBG, while for the target film 1, the grains provide a nearly flat microsurface. Figure 1 gh showcased Figure 1 cd neutralization Figure 6 Quantitative results of the height / depth line spectrum in the SnO2 surface of a further demonstrate that GSC minimization and GBG planarization can be achieved when TFSAP additives are used in film processing. A typical surface height line spectrum of the top surface of SnO2 ETL is also shown (by...). Figure 6 The dashed lines in section a) illustrate the difference in the integrity of the heterogeneous interface. Clearly, the GSC on the original grain creates significant nanopores in the micro-interface, while the target grain provided by this invention does not.

[0194] The structure of the grain-CTL microheterogeneous interface is described in detail below. For example... Figure 6AFM images of the Sn02 top surface before and after delamination were obtained as shown in FIG. 6. Since it is impractical to obtain relevant AFM images of the Sn02 ETL top and perovskite bottom from exactly the same location of the film structure, a series of AFM images were collected within a pre-marked small area of the film, and it was found that the spatial difference in morphology was negligible. Compared to the grain bottom surface, the Sn02 ETL top surface exhibited extremely low surface height fluctuation, allowing them to be approximated as flat when evaluating the micro-heterointerface. This means that in the case of the original film, when the perovskite grain bottom surface contacts the Sn02 ETL top surface, the recessed grain center inevitably results in nanoscale gaps, which are confined within the grain periphery. Such nanogaps exhibit a relatively small depth dimension, making them almost unobservable in the top-view and cross-sectional SEM images Figures 7-8 ). In contrast, when the GSC in the target film is minimized, a high degree of integrity of the grain-CTL micro-heterointerface can be achieved. Figure 9 The similar nanoscale morphology of the perovskite grain bottom surface and Sn02 top surface in the target film is illustrated, indicating a strong structural coherence due to the intimate interface contact. We ruled out the possibility that such morphology at the perovskite grain bottom is caused by TFSAP aggregates, since we applied isopropanol solvent cleaning and no change in morphology was observed Figure 10 ). It is noted that these GSC-induced nanovoids should be considered different from the GBG-induced voids and solvent-trapped induced buried voids on the heterointerface previously reported in the literature. As Figure 1 shown in FIG. 8e, the GSC-induced nanogap can span almost the entire grain, and since it exists on almost every regular grain, it is truly statistically significant. In contrast, the GBG-induced void only spans horizontally by tens of nanometers. The solvent-trapped induced void is mostly a kind of micro- or macro-volume defect randomly present at the heterointerface.

[0195] To evaluate the microstructure-adapting effect of the surfactant of TFSAP, as Figure 1 shown in FIG. 9i, in addition to the previously defined GBG angle θ, a new geometric parameter ξ is introduced herein. θ represents the angle between the tangent of the GBG side and the plane (horizontal direction) along which the perovskite compound film extends. ξ represents the angle between the connecting line of the ridge apex and the GSC center and the horizontal direction, thus roughly describing the degree of curvature relative to the ideal flat surface.

[0196] Sixty and eighty measurements were conducted to obtain the ξ and θ statistics of each film, respectively Figure 1j-k). The original film 1 contains GSC with an average value of 2.09°. In contrast, the target film 1 exhibits a significantly reduced, with most values distributed in the range of 0° to 1° (average of 0.47°), in which case all grains can be considered as non-caved. Also of interest is that, with the addition of TFSAP, the GBG angle 0 shows the same trend as the GSC angle. The target film exhibits flattened GBG with an average value of 9.9°, lower than the 15.9° of the original film. These results confirm the effectiveness of TFSAP on the adaptation of the perovskite grain surface microstructure. Although the changes in GSC and GBG angles (and ) exhibit the same trend due to their inherent formation mechanisms (to be detailed later), in addition to GBG flattening, the minimization of GSC is expected to be a key factor in building perovskite heterointerfaces with ideal microstructure and functional integrity, especially considering the greater original lateral dimension of GSC.

[0197] Formation and evolution analysis of GSC

[0198] The inventors suggest that the evolution of these GSCs is due to two main mechanism factors, as Figure 2 shown in a. The first factor is the inherent BTS generated by grain coalescence during the solution crystallization stage. As the perovskite grains grow, the side surfaces of the perovskite grains will gradually approach each other. Upon grain coalescence, it eventually leads to the combination of adjacent grain surfaces to form GBs, as shown using horizontal black dashed lines between the intragrain perovskite structures. The combination-induced biaxial interatomic force F initially causes lateral deformation xy , which in turn causes out-of-plane deformation z (annotated with a semi-transparent box) due to the overall Poisson effect (left panel). The other is the GB trench generation process driven by heat during the grain coarsening stage. Upon grain coarsening, the GB trench generation process is continuous, in which solid-state ions constantly diffuse from the trench to the flanks (middle panel). Triggered by these two processes, solid-state ions can flow plastically from the grain surface center and GBG region to the flanks, thus promoting the evolution of GSCs (right panel). In both mechanism processes, GSCs (annotated with a semi-transparent box) are formed, while flanks (annotated with a semi-transparent box) are generated (right panel). The mechanisms will be detailed below.

[0199] Once perovskite grains are formed from solution, it is expected that they will continue to grow until they come into contact with adjacent grains, leading to the generation of interatomic forces and, in turn, BTS:

[0200]

[0201] ε z_BTS = υ·ε xy_BTS (2)

[0202] where a is half of the grain size, γ s is the surface free energy per unit area, γ gb is the GB energy per unit area, M is the Young’s modulus, and v is the Poisson’s ratio. This BTS will cause ions to flow from the grain center to the side, thus creating out-of-plane deformation (ε z_BTS ). Based on this, the theoretically estimated ε z_BTS is on the order of nanometers, which is consistent with the experimentally measured deformation (ε z ) by AFM depth profiling Figure 1 g). The relative difference between ε z_BTS and ε z can be partially attributed to the yet-unaccounted contribution of the thermally driven GB trench creation process. After the grains have coalesced, the GB trench creation process starts to dominate the GSC formation, while the contribution of the GB trench creation process to the out-of-plane deformation (ε z_沟槽产生 ) is still difficult to quantify at this time. It is worth noting that GSC is more pronounced on the perovskite bottom surface than on the top surface because the top surface is free grown without the geometric boundary condition set for the bottom surface Figure 11 .

[0203] To demonstrate that the theory described above is consistent with our experimental observations in GSC formation, the possibility that other potential factors dominate GSC formation is ruled out. First, the effect of substrate roughness is explored. Figure 12 Representative AFM images of perovskite films fabricated on FTO and silicon wafer substrates are shown, which exhibit much higher and much lower roughness than the Sn02 ETL, respectively. GSC is observed in both cases generally, although there are differences in the detailed geometry. Next, although occasional bumps exist on the Sn02 ETL surface, they cannot be a major contributing factor to GSC formation considering the substantial difference in geometric features between the bumps and GSC Figure 13 . This difference is caused by different growth conditions for each grain. Some grains grow with less influence from interatomic forces of nearby grains, resulting in smaller depth of GSC (b), while some grains grow with more influence from interatomic forces of nearby grains, resulting in deeper GSC (c). Third, since the perovskite bottom surface used for AFM characterization is obtained from a mechanical exfoliation process, nanoscale flakes from the perovskite surface can be detached, which can affect the bottom surface geometry. But the experiment found that most of these statistically insignificant nanoscale flakes are taken from the GBG region of the perovskite bottom surface Figure 14 .

[0204] Based on the merging theory, from equation (1), to minimize GSC, it is required to minimize (2γ s - γ gb )1 / 2 to reduce the out-of-plane deformation ε z_BTS It is thus reasonable to employ a surfactant molecule, TFSAP additive, to tailor the GB and surface energies. As Figure 2 b (left panel), in TFSAP, the organic anion possesses two functional groups, a short perfluorinated carbon chain and a sulfo group, and is expected to interact uniformly with the perovskite surface / interface. It reduces ε z_BTS (middle panel) and suppresses ion diffusion in the GB grooves (right panel), thus minimizing the formation of GSCs. For K + cations, it does not have a significant impact on the microstructure and surface morphology, as supported by AFM observations ( Figure 15 ) when an alternative KI additive is applied at the same concentration. The organic anion of TFSAP tends to interact uniformly with the perovskite grain surface and GB through a head-to-tail configuration ( Figure 2 b middle panel), which can be attributed to two factors: (i) the polar, electron-rich sulfo group can anchor on iodide vacancies; (ii) the perfluorinated carbon chain contains the most electron pairs, which can effectively prevent self-aggregation. Thus, TFSAP can reduce the surface and GB energies and decrease the difference between them. γ s was experimentally determined using the standard OWRK method, and then γ gb was determined based on the width-depth (w-d) relationship of Mullins' GBG model. The contact angle images of water and methylene iodide were collected in Figure 16 . The values of the contact angles are listed in Table 1. The method related to OWRK is described in other methods. The obtained γ s , γ gb , and Δγ (2γ s - γ gb ) are shown in Figure 2 c, while the normalized ε z_BTS is shown in Figure 2 d. As expected, γ s decreased from 0.047 to 0.029 N m -1 , and γ gb decreased from 0.031 to 0.015 N m -1 , resulting in a normalized ε z_BTS decreasing from 1.00 to 0.82. TFSAP (with electron-rich pair- rich sulfo groups) can form coordination bonds with Pb atoms to segregate on the grain surface and GB. Simultaneously, this chemical interaction can also suppress the surface diffusion of solid-state ions. Since solid-state ion flow is mainly mediated by surface / interface vacancies, as Figure 17As shown, the ion flow can be suppressed by passivating these vacancies. The suppression of ion flow may also be related to molecular size, as larger molecules can act as a more kinetically stable barrier to the solid-state ion flow. Therefore, the solid-state ion flow during GB trench formation can be greatly mitigated. Figure 2 (b. Right subplot). These results strongly support the GSC microstructure evolution mechanism proposed in this disclosure and elucidate the role of TFSAP.

[0205] In addition to TFSAP, two other surfactant molecules were used. P-123 (P-123) and N,N,N-trimethyloctyl-1-ammonium chloride (NTAC) were used, and similar effects were achieved on the microsurface of the grains. Figure 18 Specifically, in The -OH groups at the two tails of P123 can react with organic fatty acids in perovskite. + The cations form relatively weak hydrogen bonds, while the quaternary ammonium cations of NTAC can interact with iodide ions in the perovskite. These interacting surface molecules tune the interfacial energy to relax the BTS and impede ion flow, leading to GSC elimination. Therefore, the mechanism proposed in this disclosure is applicable to both P123 and NTAC, despite their different molecular structures and interaction modes with perovskite grains. This reflects that the GSC pathway proposed in this disclosure is general and has room for future optimization.

[0206] The influence of GSC on heterogeneous interface properties

[0207] 1. Photoelectric and chemical properties of perovskite-CTL heterointerfaces

[0208] The photoelectric and chemical properties of the perovskite-CTL heterointerface were evaluated before and after the GSC engineering upgrade. Steady-state photoluminescence (PL) spectra of the two perovskite films on a quartz substrate are shown below. Figure 3 In a, this indicates a significant reduction in nonradiative recombination in the presence of GSC, which is attributed to the physical passivation effect of the free surface in GSC to reduce trap density. Figure 3 b shows the time-resolved photoluminescence (TRPL) spectra of two films deposited on SnO2-ETL-coated ITO, with and without gas-concentrated luminescent (GSC). It was found that without GSC, the average PL lifetime (τ) was significantly shorter. avg The electron extraction frequency (PL) decreased from 32.7 ns to 14.8 ns, indicating a significant enhancement in the electron extraction properties of the perovskite heterointerface. Steady-state PL measurements based on the ITO / SnO2ETL / perovskite sample structure also showed consistent results. Figure 19 To quantitatively measure the trap density, space charge confinement current (SCLC) measurements were performed on two perovskite films, such as...Figure 3 As shown in c. After the GSC engineering modification, the trap filling voltage (V) TFL The value decreased from 0.122V to 0.088V, corresponding to a decrease in trap density from 1.499 × 10⁻⁶. 14 Reduced to 1.082×10 14 cm -3 PL measurements were performed on the flipped and delaminated perovskite films, such as... Figure 20 As shown in the figure. For the target film, the peak intensity of the steady-state PL spectrum is higher. The photocarrier lifetime fitted from the TRPL spectrum (578 ns) is also longer than that of the original film (99 ns). Both indicate lower trap state intensity on the bottom surface of the target film. PL spectra of the original film and the target film on the bottom side of a SnO2 ETL-coated quartz substrate were further measured. More efficient PL quenching was observed in the target film. Figure 21 ). Figure 3 The image shows a comparison of the optical absorption spectra of perovskite films with and without GSC during accelerated aging tests (3 solar intensities and 80°C). The results are based on the normalized absorbance changes of the two films at 700 nm wavelength. Figure 22 The target film showed only a slight decrease in absorbance and remained black, while the original film degraded rapidly. This is consistent with our hypothesis that GSC-induced nanopores can act as initial degradation sites, as free bottom surfaces tend to be more severely subjected to photothermal and environmental stresses, consistent with the case of intergranular nanopores in earlier studies. Figures 23-24 The PL mapping images and X-ray diffraction (XRD) patterns also demonstrate the enhanced chemical stability of the GSC after engineering modification. TFSAP chemical functionalization may also contribute positively to these properties, such as moisture resistance. Figure 25 In addition to the influence of the transformed grain microsurface, this point should also be considered.

[0209] 2. Key thermomechanical properties of perovskite-CTL heterostructures.

[0210] Infrared-pumped visible detection (IPVP) transient absorption (TA) experiments were conducted to evaluate the heat transfer kinetics of heterojunctions with and without gas-conducting structures (GSCs), with details provided in other methods. The differential change in transmittance (dT / T) was used to assess the heat transfer capacity. Figure 3 fg shows the variation of dT / T at different delay times. Compared with the original sample, the heterointerface without GSC exhibits stronger degradation, which corresponds to faster heterointerface heat transfer. This reveals that GSC-induced nanopores hinder heat transfer in the heterointerface. Figure 26A micro-interface model for calculating the thermal conductivity k was developed, where the nanogap was simplified as a rectangular air gap. The overall k increased from 0.287 (with GSC) to 0.358 W m -1 K -1 (without GSC), which supports the results obtained in the IPVP TA experiments. Further finite element analysis (FEA) based on the model in Figure 27 was performed, and the 2D temperature distribution is shown in Figure 3 h, and the temperature line profile under internal heat source condition is shown in Figure 28 A sharp rise in temperature and inhomogeneous lateral distribution were observed in the nanogap region, proving that the GSC not only acts as an interfacial thermal resistance for vertical interfacial heat transfer, but also causes inhomogeneous temperature distribution at the bottom of the grain. The temperature distribution under external heat source condition draws the same conclusion, as shown in Figure 29 Due to these effects, thermal accumulation is expected to occur in the original perovskite film, which can lead to thermal-chemical and thermal-mechanical problems under both temperature gradients of internal and external heat sources during device durability tests. In addition, Figure 30 reveals the thermal stress accumulation at the junction point when the micro-hetero-interface with GSC is deformed at -40 °C and 85 °C, which is another stress source to break the grain-CTL physical connection under harsh temperature conditions in thermal cycling tests.

[0211] 3. Mechanical reliability of perovskite-CTL hetero-interface

[0212] To evaluate the mechanical reliability of the perovskite-CTL hetero-interface, a tape test based on the ASTM D3359 standard was adopted. This international standard is widely used to evaluate the adhesion reliability of films to substrates. The experimental process is shown in Figure 3 i. Here, a standard perovskite grid (1 x 1 mm 2 ) was pre-made onto the thin film manually by a blade. Then a glass substrate with epoxy at the corners was used as a tape to delaminate the perovskite grid from the Sn02CTL surface. The normalized delaminated area can qualitatively reflect the mechanical adhesion strength of the perovskite grain to the Sn02-ETL coated ITO. Figure 3 j-k are the photos of the residual perovskite grid (on Sn02-ETL coated ITO) under original and target sample conditions, which clearly reflect that the film adhesion is stronger without GSC. The statistical distribution of the normalized delaminated area of the two perovskite films is shown in Figure 3GSC engineering reduced the average value of normalized area of delamination from 0.740 to 0.524. The improvement in overall film mechanical reliability can be attributed to the accumulation of single micro-heterointerfaces where the grains are in complete contact with the Sn02 ETL. While the chemical interaction of TFSAP with perovskite and Sn02 in this work can have contributed to the improved adhesion strength, it is not considered to be the dominant factor. To support this, P123 and NTAC were further employed as processing additives, which led to similar elimination of GSC, but these additives are not expected to exhibit very significant chemical interaction with Sn02 or perovskite. However, similar levels of improvement in interfacial adhesion strength were still observed with TFSAP, as shown in Figure 31

[0213] Meanwhile, for the case of potassium trifluoromethanesulfonate (PTFS) which contains the same functional group as TFSAP, although it could not planarize GSC Figure 32 ), no significant improvement in adhesion strength was observed Figure 31 ). The advantage of non-recessed grains can be further amplified when using interfacial molecular glue, which in turn demonstrates the microstructure effect. The interfacial glue of iodine-terminated self-assembled monolayer (I-SAM) ((3-iodopropyl)trimethoxysilane (Si(OCH3)3(CH2)3I)) between perovskite grains and ETL, which has been reported, was tested. As shown in Figure 3 , with the use of I-SAM, the target films can demonstrate further enhanced interfacial adhesion, with the average value reduced from 0.291 to 0.118. It can be observed that the deposition of I-SAM on the Sn02 ETL surface has a more significant contribution to the improvement in interfacial reliability compared to GSC minimization alone. However, due to the GSC minimization increasing the interfacial contact area, its incorporation via I-SAM further facilitates the formation of more effective interfacial hydrogen bonds. To provide a more intuitive illustration, the delamination experimental results were grouped according to the ASTM D3359 standard to rate the adhesion, ranging from 0B to 5B, where 0B represents the worst adhesion strength and 5B represents the best adhesion strength, as shown in Figure 3 . The distribution of 0B-5B matches Figure 3 the results in Figure 33 , where the target groups without GSC generally obtained better adhesion ratings. It is expected that the planar grains will create more molecular bonds at the center of the grains, thus demonstrating interfacial adhesion, as shown in

[0214] Effect of GSC on PSC device performance and durability ​

[0215] 1. Photovoltaic performance of PSCs

[0216] The impact of GSC minimization on the photovoltaic performance and durability performance of the devices was evaluated, where the conventional device structure was ITO / Sn02 ETL / perovskite film / Spiro-OMeTAD / Au. Figure 4a Current density-voltage (J-V) curves of the best PSC devices under reverse scan are shown for the pristine and target films. To explore the efficiency potential, the minimization of GSC at the grain-CTL heterointerface significantly improved the photovoltaic performance of the devices, leading to a PCE of 25.5%, with an open-circuit voltage (V OC ) of 1.21 V, a short-circuit current density (J SC ) of 25.69 mA cm -2 , and a fill factor (FF) of 0.82. The external quantum efficiency (EQE) spectrum of this PSC device with an integrated J -2 of 24.60 mA cm SC is shown in Figure 4b As a comparison, the best PSC prepared with the pristine film showed a PCE of 23.3% with a V OC of 1.17 V, a J SC of 25.17 mA cm -2 , and a FF of 0.79. Figure 4c The PCE statistical distribution of the devices with and without GSC is shown. The significant improvement in V OC and FF can be explained by the enhanced electron extraction and reduced non-radiative recombination in the perovskite film without GSC Figure 3 (a-c). This improvement can be mainly attributed to the improved functional integrity of the microheterointerfaces due to GSC minimization.

[0217] 2. Durability of PSCs under different external stress sources

[0218] The durability results of PSCs were then obtained under different external stress sources following the international standard protocols as shown in Figure 4d -f. Although the Spiro-OMeTAD hole transport layer (HTL) was considered to have an uncertain impact on the device durability results, the use of Spiro-OMeTAD hole transport layer was suitable for demonstrating the efficiency potential. Therefore, the PSC devices used for these durability tests all adopted PTAA.

[0219] First, the PCE change of PSCs under thermal fatigue stressor was monitored. The thermal cycling test was performed in a program-controlled environmental chamber following ISOS-T-3 protocol, which requires thermal cycling from -40 °C to 85 °C. For PSCs without GSC, typically, 83% of the initial PCE was still retained after 300 temperature cycles Figure 4d ), which is much better than that of conventional PSCs (40%). It is noted that the initial PCEs of devices with and without GSC are typically 19.9% and 21.0%, respectively, in ISOS-T-3 test. Figure 4g The periodic compression-tension strain caused by the difference in thermal expansion coefficient on the perovskite heterointerface during thermal cycling test was illustrated Figure 30 ). Unlike the case of non-recessed grains, GSC locally breaks the structural integrity of the micro-heterointerface and leaves behind nanovoids contained at the grain-CTL micro-heterointerface, which only leads to a weak physical connection based on the grain ridges, as shown in the right panel. This weak connection can easily cause delamination under interface fatigue Figure 30 ), due to the abnormal increase of interfacial stress in the micro-interface with GSC. Figure 34 It is confirmed that severe grain degradation and interface delamination occur after 300 thermal cycles for the case of original samples, while the high integrity of the grain-CTL micro-heterointerface is preserved for the case of non-recessed samples. Next, it is expected that the presence of these GSC-induced nanovoids can accommodate moisture and hinder heat transfer at the micro-heterointerface in a damp-heat test, as shown in the inset of Figure 4h ). GSC can effectively facilitate moisture intrusion and hinder grain-CTL heat transfer, leading to the accumulation of moisture and heat at the micro-heterointerface. Following ISOS-D-3 protocol, device durability was evaluated under damp-heat conditions (85 °C, 85% RH). Typically, PSCs without GSC can maintain 90% of their initial efficiency after 660 hours (h) of testing Figure 4e ), while conventional PSCs show only 45%. It is noted that the initial PCEs of devices with and without GSC are typically 20.3% and 21.5%, respectively, in ISOS-D-3 test. The elimination of nanovoids in the buried heterointerface, which are natural hosts for moisture molecules, and the uniform distribution of TFSAP on the interface with hydrophobic fluorocarbon chains contribute to better humidity durability of the target device Figure 25 ). The uniform lateral temperature distribution and the facilitated grain-Sn02 heat transfer also contribute to better high-temperature durability of the target device Figure 3 f-h). In addition, maximum power point (MPP) tracking test was performed following ISOS-L-l l protocol. Typically, PSCs without GSC still retain 90% of the initial PCE after 1290 h of MPP operation Figure 4f), while the regular device only sustains 144 h, then the initial PCE drops to 90%. It is noted that the initial PCE of the devices with and without GSC are typically 20.5% and 21.4%, respectively, in ISOS-L-11 test. Since GSC introduces more free microsurfaces that are not physically passivated by the Sn02 ETL, GSC can act as a vulnerable site where stoichiometry loss can occur at the shown side Figure 4i It is not surprising that the perovskite film without GSC has better photothermal stability, as evidenced by the better PL intensity of the film without GSC Figure 3 d-e). Moreover, the excess photogenerated carriers located at the GSC cannot be efficiently extracted by the Sn02 ETL Figure 3 b), which can cause charge accumulation and accelerate perovskite degradation via enhanced ionic activity. The combination of excellent thermal cycling performance, damp-heat performance, and MPP tracking stability can be comparable to the best cases in the literature.

[0220] Finally, confirming the positive impact of GSC minimization requires excluding the possible contribution of chemical passivation by surfactants and GBG planarization. In this regard, by optimizing the TFSAP addition amount, a strong consistency between the change trend of GSC angle and device PCE can be observed. The optimal concentration of TFSAP in the perovskite precursor solution can be 0.3-0.9 mg / ml.

[0221] Moreover, when adding sodium dodecylbenzenesulfonate (SDBS; a classic surfactant molecule with sulfonic acid group) and PTFS (a shorter fluorocarbon chain than TFSAP), the impact of these two molecules on changing the GSC geometry is limited when applied at the same additive concentration as TFSAP, as shown in Figure 32 Although both compounds are expected to exhibit similar chemical passivation effects at the molecular scale as TFSAP, we did not observe any significant increase in PL intensity and device PCE under the specific experimental conditions Figure 35 ). Therefore, it can be inferred that the contribution of TFSAP to the device improvement mainly comes from the observed optimization of GSC geometry, rather than its possible chemical passivation effect. Moreover, perovskite films with GBG planarized to a similar angle Θ were fabricated using a previously reported method. The AFM images of the perovskite bottom surface and the statistical distribution of GBG angle Θ are shown in Figure 36 Compared to the method used in this disclosure, the J-V performance and device stability show a lower level of improvement, which indicates the important role of GSC minimization to the overall device improvement.

[0222] While finding effective GSC elimination helps improve device performance, there can be other potential impacts. Take the P123 case as an example, to induce GSC elimination, a relatively high additive concentration was used, which resulted in insulating surfaces and thus relatively limited PCE increase. Figure 37

[0223] In summary, the present disclosure reveals a previously overlooked microstructure - GSC, and elucidates its microstructural evolution process, and its detrimental impact on the structural integrity, charge extraction, chemical stability, and thermo-mechanical reliability of the buried perovskite grain-CTL heterointerface. By using a surfactant molecule (e.g., TFSAP) to minimize GSC, a robust perovskite heterointerface was successfully constructed in a PSC, with a near-ideal micro-heterointerface segment in composition. The resulting PSC not only provides an improved PCE of 25.5%, but also retains 83%, 90%, and 90% of its initial efficiency after 300 thermal cycles (ISOS-T-3 protocol), 660 h damp-heat exposure (ISOS-D-3 protocol), and 1290 h MPP operation (ISOS-L-11 protocol), respectively. The present disclosure highlights a critical but overlooked perovskite surface microstructure type, and its important impact on PSC performance and durability. The in-depth understanding of the microstructure-property-performance relationship gained from the work in the disclosure can add to the established understanding and help contribute to the extensive efforts paid to develop efficient and stable PSCs and other optoelectronic devices.

[0224] Other methods

[0225] OWRK method. In the OWRK method, Young’s equation is written as a force balance at the three-phase contact point where air, liquid, and solid meet

[0226] γ sv = γ sl + γ lv cos θ (1)

[0227] where γ sv is the surface free energy of the solid, γ sl is the interfacial tension between the liquid and the solid, γ lv is the surface tension, and θ is the contact angle. The work of adhesion is defined as:

[0228] W a = γ sv + γ lv - γ sl = γ lv (1 + cos θ) (2)

[0229] The combining rule proposed by the OWRK model is shown below:

[0230] ​

[0231] where γ sv D and γ lv D are the dispersive components, γ sv P and γ lv P are the polar components of the solid and liquid surface energies, respectively. In combination with the Young's equation, one obtains

[0232]

[0233] If the dispersive and polar components of the probing liquid are known, there are two unknown parameters γ sv D and γ sv P . Based on this, H2O and diiodomethane with known dispersive and polar parts of the surface tension were chosen to calculate the solid surface free energy, whose parameters are listed in Table 2.

[0234] Mullins GBG model. The GB energy γ gb was determined using the Mullins GBG model, which can be calculated by the following equation:

[0235]

[0236] where m is a constant typically equal to 4.73, w is the GBG width, and d is the GBG depth. The surface energy γ s was determined by the OWRK method. The depth and width values were measured using the NanoScope analysis software (V1.8). A total of 40 measurements of the trench width and depth and their average were used to determine the value of γ gb in c. Figure 3

[0237] GSC microstructure evolution induced by BTS. A quantitative physical model is presented in this disclosure to deduce the GSC formation process of BTS and to explore the effect of TFSAP on planarized GSC. The model provides a simplification by representing the perovskite crystallites as a perfect regular array of hexagonal crystallites to simulate the grain coalescence process. The size of each hexagonal crystallite is 2a and the height is h. The out-of-plane spacing between neighboring crystallites is denoted as Δ. Let γ1 represent the crystallite surface energy, γ2 represent the grain boundary energy, M represent the Young's modulus, and v represent the Poisson's ratio. The free energy E1 of each crystallite per unit film area before coalescence can be represented as

[0238]

[0239] ​where E0represents the free energy per unit area of the top and bottom surfaces, and the second term represents the free energy per unit area of the side surfaces. When the crystallites coalesce, each crystallite is subjected to biaxial elastic strain to fill the gap, resulting in an out-of-plane strain ε = Δ xy / 2a. In this process, two side surfaces will be consumed to form new grain boundaries. The free energy per unit film area of each crystallite before coalescence, E2, can be expressed as

[0240]

[0241] where the second term represents the grain boundary free energy per unit area, and the third term represents the strain energy per unit area. M / (1 - v) represents the biaxial modulus of the crystallite. Here, we do not consider the anisotropy of the crystallite and the constraint from the substrate. When E2< E1, the grain coalescence process is spontaneous. When E2= E1, the maximum out-of-plane deformation Δ 最大 can be calculated, and we can determine the maximum biaxial tensile stress σ 最大 :

[0242]

[0243] where γ s and γ gb are the surface energy and GB energy per unit area, respectively. The biaxial tensile stress can be very high even for small crystallites. Considering the small Young’s modulus during heat-induced coalescence and the presence of grain surface ion plastic flow, we speculate that the surface deformation occurs via biaxial ion plastic flow to release this high stress, eventually leaving a depression on the grain surface.

[0244] It is noted that the theory described above is only applicable to the standard case where each grain contains only one GSC, which is applicable to the analysis of the perovskite films with standard thickness (about 300 nm) in the work of this disclosure. In fact, we observed in the experiments that when the film thickness exceeds the standard thickness, it is clear that one grain can contain multiple GSCs, which requires modification of the theory for further explanation of GSC formation.

[0245] Multi-scale FEA simulation

[0246] The simulation of the micro-hetero-interface was performed using finite element analysis. The thermo-mechanical parameters of the materials are collected in Table 3.

[0247] To simulate the heat transfer at the micro-interface, only the perovskite layer and the adjacent Sn02layer were induced. The dimensions of the perovskite layer and the Sn02layer were set at 500 x 300 nm 2 and 500 x 30 nm 2The GSC was modeled by adding a crescent shaped air gap with a length of 460 nm and a depth of 10 nm at the interface. In the case of internal heat source, the middle region of the perovskite film needs to be a heat source with constant high temperature. Therefore, the height of the perovskite grain was reset to 150 nm and the top boundary (corresponding to the middle region) was set to high temperature. In the models with and without GSC, we divided the geometry into 3464 and 2324 triangular elements, respectively. In the solid heat transfer simulation, the interfacial thermal resistance was not considered. The boundaries without initial temperature setting were treated as thermally insulated boundaries.

[0248] For the thermal stress and solid elastic deformation simulation, the Au layer (80 nm), Spiro-OMeTAD layer (30 nm), perovskite layer (300 nm), Sn02 layer (30 nm), and ITO layer (140 nm) were all constructed to take the device integrity into account. The modeling of GSC was the same as the heat transfer simulation. In the models with and without GSC, we divided the geometry into 2564 and 1704 triangular elements, respectively. To simplify the calculation, we did not construct the glass substrate with a thickness of 1.1 mm. But considering the limitation of thick glass substrate, we set the ITO layer bottom boundary as a rigid boundary. After setting the temperature boundary conditions, the temperature distribution was calculated first. Then the temperature values were used as the initial values for the subsequent thermal stress and elastic deformation simulation.

[0249] The experimental data disclosed is intended to establish the feasibility and reproducibility of the claimed process under representative conditions. The materials and process parameters selected reflect the desired results and are consistent with standard practice in the art. The focus of the present disclosure is to demonstrate the feasibility of the process under the particular conditions described. While the experimental data provided focuses on specific conditions, the process is not intended to be limited to these embodiments. The methods described herein are adaptable to a range of conditions, and variations in the various components can be explored to optimize the process for a particular application. The selection of the parameters is based on their practical relevance and consistency with the objectives of the invention.

Claims

1. A perovskite layer comprising a perovskite compound and a surfactant, wherein the perovskite compound is represented by Formula 1: (A + ) 1-y (A’ + ) y (M 2+ )(X - )3 1 Where y is 0.01-0.99; M 2+ It is Pb 2+ Sn 2+ Or Ge 2+ ; A + and A' + Each of them is independently Cs + 、Rb + CH3NH3 + CH3CH2NH3 + H(C=NH2)NH2 + Or Me(C=NH2)NH2 + ;and X - F is independent in each case. - Cl - ,Br - Or I - A + and A' + Same or different; and The surfactants include sulfonate surfactants, alcohol alkoxylate surfactants, quaternary ammonium surfactants, or mixtures thereof.

2. The perovskite layer of claim 1, wherein the sulfonate surfactant comprises halogenated C4-C 12 Alkyl-substituted sulfonic acid groups.

3. The perovskite layer of claim 1, wherein the quaternary ammonium surfactant comprises one or more C1-C... 16 Alkyl substituents.

4. The perovskite layer of claim 1, wherein the surfactant comprises one or more of the following: potassium perfluorohexane-1-sulfonate, sodium perfluorohexane-1-sulfonate, potassium perfluorobutane-1-sulfonate, sodium perfluorobutane-1-sulfonate, potassium perfluorodecane-1-sulfonate, sodium perfluorodecane-1-sulfonate, poly(ethylene oxide) / poly(propylene oxide) (EO / PO) block copolymer, or N,N,N-trimethyloctyl-1-ammonium chloride.

5. The perovskite layer as claimed in claim 1, wherein M 2+ It is Pb 2+ And A + and A' + Each of them is independently Cs + CH3NH3 + or H(C=NH2)NH2 + .

6. The perovskite layer of claim 1, wherein the perovskite layer comprises (H(C=NH2)NH2) + ) 1-y (Cs + ) y (Pb 2 + (I) - )3, where y is 0.01-0.

99.

7. The perovskite layer of claim 1, wherein the perovskite layer comprises a perovskite compound of formula 2: [(A + ) 1-y (A’ + ) y (M 2+ )(X - )3] 1-z [(A” + )(M’ 2+ )(Q - )3] z 2 Where y is 0.01-0.99; z is 0.01-0.99; M 2+ It is Pb 2+ Sn 2+ Or Ge 2+ ; M' 2+ It is Pb 2+ Sn 2+ Or Ge 2+ ; A + A' + and A” + Each of them is independently Cs + 、Rb + CH3NH3 + CH3CH2NH3 + H(C=NH2)NH2 + Or Me(C=NH2)NH2 + ;and X - and Q - F is independent in each case. - Cl - ,Br - Or I - A + and A' + Same or different.

8. The perovskite layer of claim 7, wherein M 2+ and M' 2+ Each of them is Pb 2+ A + and A' + Each of them is independently Cs + CH3NH3 + or H(C=NH2)NH2 + ;and A” + It is CH3NH3 + .

9. The perovskite layer of claim 7, wherein the perovskite layer comprises [(H(C=NH2)NH2] + ) 1-y (Cs + ) y (Pb 2+ (I) - )3] 1-z [(CH3NH3 + (Pb) 2+ (Br) - )3] z , where y is 0.01-0.99 and z is 0.01-0.

99.

10. The perovskite layer of claim 1, wherein the perovskite layer comprises a plurality of perovskite grains, and each of the plurality of perovskite grains has a bottom surface comprising a single grain surface depression (GSC) and a ridge surrounding the GSC, and wherein the average angle ξ of the perovskite grain between the line connecting the apex of the ridge and the center of the GSC and the top surface opposite the bottom surface of the grain is 0°-1.5°.

11. The perovskite layer of claim 1, wherein the perovskite layer comprises a plurality of perovskite grains and grain boundary trenches (GBGs) located between the bottom surfaces of each adjacent perovskite grain, the GBGs being surrounded by the edges of the adjacent perovskite grains as GBG sidewalls, and wherein the average angle θ between the tangent of the perovskite grain to the GBG sidewall and the top surface opposite the bottom surface of the grain is 0°-15°.

12. A method for producing a perovskite layer as described in any one of claims 1-11, wherein the method comprises: A perovskite precursor solution is provided, the perovskite precursor solution comprising one or more metal salts, each independently represented by the formula MX2, two or more salts, each independently represented by the formula AZ, the surfactant, and a solvent, wherein M is Pb. 2+ Sn 2+ Or Ge 2+ A is Cs + 、Rb + CH3NH3 + CH3CH2NH3 + H(C=NH2)NH2 + Or Me(C=NH2)NH2 + X is F independently in each case. - Cl - ,Br - Or I - And Z is F independently in each case. - Cl - ,Br - Or I - ; The perovskite precursor solution is deposited on the surface of the charge transport layer to form a wet film; and The wet film is annealed to form the perovskite layer.

13. The method of claim 12, wherein the perovskite precursor solution comprises (Cs) + (I) - ), (H(C=NH2)NH2 + (I) - (Pb) 2+ (I) - )2 and perfluorohexane-1-sulfonate.

14. The method of claim 12, wherein the perovskite precursor solution comprises (Cs) + (I) - ), (H(C=NH2)NH2 + (I) - (CH3NH3) + (Cl) - (Pb) 2+ (I) - 2. (CH3NH3) + (Pb) 2+ (Br) - )3 and perfluorohexane-1-sulfonate.

15. The method of claim 12, wherein the surfactant has a concentration of 0.1-5 mg / ml in the perovskite precursor solution.

16. The method of claim 12, wherein the one or more metal salts have a concentration of 0.5-2.0 M in the perovskite precursor solution.

17. An optoelectronic device comprising a perovskite layer as claimed in any one of claims 1-11.

18. The optoelectronic device of claim 17, wherein the optoelectronic device is a perovskite solar cell (PSC), a perovskite light-emitting diode, a perovskite laser, or a perovskite photodetector.

19. The optoelectronic device of claim 18, wherein the perovskite solar cell comprises an interfacial adhesive layer located between the perovskite compound film and an adjacent charge transport layer.

20. The optoelectronic device of claim 18, wherein the photoelectric conversion efficiency of the perovskite solar cell is 23.5%-25.5%.

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