Perovskite solar cells containing interfacial layers

Abstract

A photovoltaic cell comprising a perovskite layer (110), an electron transport layer (106), and an interfacial layer (108) disposed between the electron transport layer and the perovskite layer, the interfacial layer comprising a metallocene substituted with a substituent having an O, S, N or P group, e.g., ferrocene substituted with a thienyl-carboxylate group.

Description

[Technical field]

[0001] The present application relates to materials for interfacial layers for metal halide perovskite solar cells and to photovoltaic cells including the interfacial layers. [Background technology]

[0002] Metal halide perovskites are inexpensive and simple to manufacture through a wide variety of fabrication processes and techniques. Metal halide perovskites are commonly used in the light absorbing layer in thin-film solar cells, leading to low-cost, lightweight solar cells. Such metal halide perovskite solar cells (metal halide PVSCs) have emerged as a breakthrough photovoltaic technology, with power conversion efficiencies (PCEs) of 25.5% being achieved in single-junction PVSCs. PVSCs exceed the efficiency of currently commercialized thin-film solar cells (e.g., cadmium telluride, CdTe, or copper indium gallium selenide, CIGS) and approach the efficiency of state-of-the-art crystalline silicon solar cells.

[0003] WO2017160955 discloses perovskite-based photoactive devices, such as solar cells, that include an insulating tunnel layer interposed between a perovskite photoactive material and an electron collecting layer.

[0004] China Patent No. 113193124 discloses a triethylamine hydrochloride modified perovskite solar cell comprising, in sequence, a transparent conductive glass, a tin dioxide electron transport layer, a triethylamine hydrochloride layer, a perovskite absorber layer, a hole transport layer and a metal electrode.

[0005] WO2015092397 discloses photovoltaic and optoelectronic devices comprising a passivated metal halide perovskite, the device comprising: (a) a metal halide perovskite; and (b) a passivation agent that is an organic compound; wherein the molecules of the passivation agent are chemically bonded to anions or cations in the metal halide perovskite.

[0006] WO2018137048 discloses perovskite-based optoelectronic devices using an electron transport layer formed with a perovskite layer that is passivated using ligands selected to reduce electron-hole recombination at the interface between the electron transport layer and the perovskite layer.

[0007] China Patent No. 110993803 discloses the formation of passivation layers at the perovskite grain boundaries and the perovskite / hole transport layer interface in perovskite solar cells.

[0008] China Patent No. 109360889 discloses a solar cell comprising, from bottom to top, a transparent conductive substrate, a hole transport layer, a perovskite thin film, an interface passivation layer, an electron transport layer and a cathode.

[0009] Organic interface materials (OIMs) are known. These organic materials offer flexibility, uniformity and multifunctionality as interlayers in PVSCs. However, OIMs typically exhibit poor conductivity and carrier mobility, and form interfacial barriers that impede charge carrier transport. Furthermore, they exhibit chemical or photochemical instability that can affect the long-term stability of photovoltaic devices.

[0010] Inorganic interface materials (IIMs) are also known for PVSCs. Such IIMs typically have inherent thermal and chemical stability and exhibit high carrier conductivity and good stability as interlayers in PVSCs. However, they are structurally rigid (not as flexible as organic materials) and prevent intimate contact and interaction with the perovskite surface. Furthermore, some inorganic interface materials (e.g., 2D transition metal chalcogenides) exhibit inhomogeneous coverage at the perovskite surface, which can result in additional non-radiative recombination.

[0011] Poor lifetime and instability continue to affect the commercial prospects of PVSCs. It would be desirable to address these shortcomings with PVSCs and to provide stable and efficient photovoltaic cells. Summary of the Invention

[0012] In a first aspect, the present invention provides a method for producing a method of treating a disease comprising: 1st electrode; second electrode; a perovskite layer and an electron transport layer disposed between first and second electrodes; and An interfacial layer between the perovskite layer and the electron transport layer The interfacial layer is in direct contact with the perovskite layer. The interfacial layer has at least one substituent R containing at least one of O, S, N or P atoms. 1 The interfacial compound comprises or consists of a metallocene-containing interfacial compound substituted by:

[0013] Optionally, the interfacial compound is a compound of formula (I): [Metallocene]p (I) During the ceremony: The metallocene is a compound having two aromatic or heteroaromatic groups Ar 1 a metallocene group comprising a metal bonded to p is at least 1; At least one metallocene has at least one substituent R 1 has been replaced by; It is.

[0014] Optionally, the compound of formula (I) has formula (Ia): [ka] During the ceremony: M is a metal ion; Ar 1 is, at each occurrence, a monocyclic or polycyclic aromatic or heteroaromatic group; M and two Ar 1the groups form a metallocene; At least one Ar 1 But there is at least one R 1 has been replaced by; R 2 is a group that satisfies the valence of M; q is 0 or a positive integer; R 3 is, at each occurrence, independently H or a substituent; has.

[0015] Optionally, the metallocene is ferrocene.

[0016] Optionally, R 1 is a group of formula (II): -AB (II) In the formula, A is a divalent group containing O, S, N or P; B is H, C 1-12 alkyl, optionally substituted aryl, or optionally substituted heteroaryl; It is.

[0017] Optionally, A has the formula: -(R 5 ) f -Z-(R 5 )g-(III) -(R 6 O) j - (IV) During the ceremony: R 5 is, at each occurrence, independently a hydrocarbon group; f and g are each independently 0 or 1; R 6 But, C 1-4 an alkylene group, preferably ethylene; Z is O, S, COO, C(=S)O, C(=O)S, CONR 4 , CSNR 4 , OC(=O)O, OC(=O)NR 4 ,OC(=O)PR 4、 NR 4 , P.R.4 ,-OP(=O)(OR 4 )-O-, -NR 4 -P(=O)(NR 4 2)-NR 4 - and R 4 is H, optionally substituted C 1-12 alkyl or optionally substituted phenyl; is selected from the group:

[0018] In some preferred embodiments, the metallocene and R 1 The bond between the metallocene C atom and the R 1 It is a carbon-oxygen bond attached to the O atom of

[0019] Optionally, A is -OC(=O)-.

[0020] Optionally, B is selected from optionally substituted phenyl and optionally substituted 5-membered heteroaryl containing one or more ring atoms selected from O, S and N.

[0021] Optionally, B is an optionally substituted thiophene.

[0022] Optionally, the perovskite layer comprises a perovskite of formula CatPbX3 or CatSnX3, where Cat is a metal cation, an organic cation, or a combination thereof, and X is selected from at least one of I, Br, and Cl.

[0023] Optionally, the electron transport layer comprises a fluorene.

[0024] In a second aspect, the present invention provides a photovoltaic module comprising a plurality of photovoltaic cells according to any one of the preceding claims, wherein the photovoltaic cells are connected in series.

[0025] In a third aspect, the present invention provides a compound of formula (I): [Metallocene]p (I) During the ceremony: The metallocene is a compound having two aromatic or heteroaromatic groups Ar 1 a metallocene group comprising a metal bonded to p is at least 1; At least one metallocene has at least one substituent R 1 is replaced by R 1 Is of formula (II): -AB (II) wherein A is a divalent group containing O, S, N, or P; B is an optionally substituted aryl or an optionally substituted heteroaryl; is the basis of; The present invention provides a compound of the formula:

[0026] According to a third embodiment, optionally, Ar 1 is an optionally substituted cyclopentadienyl.

[0027] Optionally according to the third embodiment, the metallocene is ferrocene.

[0028] Optionally according to a third embodiment, A has the formula: -(R 5 ) f -Z-(R 5 )g-(III) -(R 6 O) j - (IV) During the ceremony: R 5 is, at each occurrence, independently a hydrocarbon group; f and g are each independently 0 or 1; R 6 But, C 1-4 an alkylene group, preferably ethylene; j is 1 to 10; Z is O, S, COO, C(=S)O, C(=O)S, CONR 4, CSNR 4 , OC(=O)O, OC(=O)NR 4 ,OC(=O)PR 4、 NR 4 , P.R. 4 ,-OP(=O)(OR 4 )-O-, -NR 4 -P(=O)(NR 4 2)-NR 4 - and R 4 is H, optionally substituted C 1-12 alkyl or optionally substituted phenyl; is selected from the group:

[0029] Optionally according to a third aspect, A is -OC(=O)-.

[0030] Optionally according to a third aspect, B is selected from optionally substituted phenyl and optionally substituted 5-membered heteroaryl containing one or more ring atoms selected from O, S and N.

[0031] Optionally according to the third embodiment, B is an optionally substituted thiophene. [Brief description of the drawings]

[0032] [Figure 1A] FIG. 1A provides a schematic diagram of a conventional perovskite solar cell including an interfacial layer, and FIG. 1B provides a schematic diagram of an inverse perovskite solar cell including an interfacial layer. [Figure 1B] FIG. 1A provides a schematic diagram of a conventional perovskite solar cell including an interfacial layer, and FIG. 1B provides a schematic diagram of an inverse perovskite solar cell including an interfacial layer. [Diagram 2] FIG. 2 shows substituted metallocenes suitable for use in the interfacial layer. [Figure 3A]FIG. 3A provides a schematic diagram of the example inverted perovskite solar cell of FIG. 1B including FcTc2 interfacial functionalization material, FIG. 3B shows a cross-sectional SEM image of a fabricated inverted PVSC having the structure of FIG. 3A, and FIG. 3C shows TOF-SIMS characterization of the perovskite solar cell of FIG. 3B. [Figure 3B] FIG. 3A provides a schematic diagram of the example inverted perovskite solar cell of FIG. 1B including FcTc2 interfacial functionalization material, FIG. 3B shows a cross-sectional SEM image of a fabricated inverted PVSC having the structure of FIG. 3A, and FIG. 3C shows TOF-SIMS characterization of the perovskite solar cell of FIG. 3B. [Figure 3C] FIG. 3A provides a schematic diagram of the example inverted perovskite solar cell of FIG. 1B including FcTc2 interfacial functionalization material, FIG. 3B shows a cross-sectional SEM image of a fabricated inverted PVSC having the structure of FIG. 3A, and FIG. 3C shows TOF-SIMS characterization of the perovskite solar cell of FIG. 3B. [Figure 4A] FIG. 4A shows X-ray photoelectron spectroscopy (XPS) characterization of the binding energy of Pb, FIG. 4B shows XPS characterization of N, and FIG. [Figure 4B] FIG. 4A shows X-ray photoelectron spectroscopy (XPS) characterization of the binding energy of Pb, FIG. 4B shows XPS characterization of N, and FIG. [Figure 4C] FIG. 4A shows X-ray photoelectron spectroscopy (XPS) characterization of the binding energy of Pb, FIG. 4B shows XPS characterization of N, and FIG. [Figure 5A] FIG. 5 shows surface potential images of the perovskite film obtained by scanning Kelvin probe microscopy, with the bottom graph showing the statistical potential distribution on the film surface of a control device (FIG. 5A) and an FcTc2-treated perovskite film including an interfacial layer (FIG. 5B). [Figure 5B] FIG. 5 shows surface potential images of the perovskite film obtained by scanning Kelvin probe microscopy, with the bottom graph showing the statistical potential distribution on the film surface of a control device (FIG. 5A) and an FcTc2-treated perovskite film including an interfacial layer (FIG. 5B). [Figure 6]FIG. 6 shows the time resolved photoluminescence (TRPL) spectra of a device comprising perovskite / FcTc2 / C60 (with an interfacial layer) and a device comprising perovskite / C60 (control). [Figure 7] Figure 7 shows the steady-state PL spectra of perovskite films with different concentrations of FcTc2 (0, 0.5, 1.0 and 2.0 mg mL-1) excited via a laser with a wavelength of 485 nm. [Figure 8A] FIG. 8 shows PFIR microscopy at an IR frequency of 1480 cm (resonant with the CN stretch absorption of the MA+ ion): FIG. 8A shows the FcTc2 modified perovskite film before illumination, FIG. 8B shows the FcTc2 modified perovskite film after illumination for 1000 hours at 85° C., FIG. 8C shows the control perovskite film before illumination, and FIG. 8D shows the control perovskite film after illumination for 1000 hours at 85° C. [Figure 8B] FIG. 8 shows PFIR microscopy at an IR frequency of 1480 cm (resonant with the CN stretch absorption of the MA+ ion): FIG. 8A shows the FcTc2 modified perovskite film before illumination, FIG. 8B shows the FcTc2 modified perovskite film after illumination for 1000 hours at 85° C., FIG. 8C shows the control perovskite film before illumination, and FIG. 8D shows the control perovskite film after illumination for 1000 hours at 85° C. [Figure 8C] FIG. 8 shows PFIR microscopy at an IR frequency of 1480 cm (resonant with the CN stretch absorption of the MA+ ion): FIG. 8A shows the FcTc2 modified perovskite film before illumination, FIG. 8B shows the FcTc2 modified perovskite film after illumination for 1000 hours at 85° C., FIG. 8C shows the control perovskite film before illumination, and FIG. 8D shows the control perovskite film after illumination for 1000 hours at 85° C. [Figure 8D]FIG. 8 shows PFIR microscopy at an IR frequency of 1480 cm (resonant with the CN stretch absorption of the MA+ ion): FIG. 8A shows the FcTc2 modified perovskite film before illumination, FIG. 8B shows the FcTc2 modified perovskite film after illumination for 1000 hours at 85° C., FIG. 8C shows the control perovskite film before illumination, and FIG. 8D shows the control perovskite film after illumination for 1000 hours at 85° C. [Figure 9] FIG. 9 shows the JV curves of the best performing devices, with and without the FcTc2 interfacial layer. [Figure 10] FIG. 10 shows the EQE spectra and integrated current densities of the best performing devices with and without FcTc2. [Figure 11] FIG. 11 shows a histogram of measured PCE values ​​among 30 devices with and without FcTc2. [Figure 12] FIG. 12 shows the normalized PCE values ​​of unencapsulated PVSCs with and without FcTc2 measured at the maximum power point (MPP) under one continuous solar illumination at room temperature in a N2 atmosphere. [Figure 13A] FIG. 13 shows the results of stability studies based on non-encapsulated devices with and without FcTc2 under continuous heating at 85° C. in a N2 atmosphere (FIG. 13A) and stored in ambient air (RH 40-50%, 25° C.) in the dark (FIG. 13B). [Figure 13B] FIG. 13 shows the results of stability studies based on non-encapsulated devices with and without FcTc2 under continuous heating at 85° C. in a N2 atmosphere (FIG. 13A) and stored in ambient air (RH 40-50%, 25° C.) in the dark (FIG. 13B). [Figure 14A] FIG. 14 shows normalized PCE data for an encapsulated device stored at 85% RH and 85° C. in the dark (FIG. 14A) and from −40° C. (15 min dwell) to 85° C. (15 min dwell) with a ramp rate of 100° C. / hr (FIG. 14B). [Figure 14B]FIG. 14 shows normalized PCE data for an encapsulated device stored at 85% RH and 85° C. in the dark (FIG. 14A) and from −40° C. (15 min dwell) to 85° C. (15 min dwell) with a ramp rate of 100° C. / hr (FIG. 14B). [Figure 15A] FIG. 15A shows the JV curves of the best performing MAPbI3-based PVSCs with and without FcTc2, and FIG. 15B shows the histogram of measured PCE values ​​among 20 devices of MAPbI3-based PVSCs with and without FcTc2. [Figure 15B] FIG. 15A shows the JV curves of the best performing MAPbI3-based PVSCs with and without FcTc2, and FIG. 15B shows the histogram of measured PCE values ​​among 20 devices of MAPbI3-based PVSCs with and without FcTc2. [Figure 16A] FIG. 16A shows the JV curves of the best performing Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3-based PVSCs with and without FcTc2, and FIG. 16B shows the histogram of measured PCE values ​​among 20 devices of Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3-based PVSCs with and without FcTc2. [Figure 16B] FIG. 16A shows the JV curves of the best performing Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3-based PVSCs with and without FcTc2, and FIG. 16B shows the histogram of measured PCE values ​​among 20 devices of Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3-based PVSCs with and without FcTc2. [Figure 17A] FIG. 17A shows the JV curves of the best performing FAPbI3-based PVSCs with and without FcTc2, and FIG. 17B shows the histogram of measured PCE values ​​among 20 devices of FAPbI3-based PVSCs with and without FcTc2. [Figure 17B]FIG. 17A shows the JV curves of the best performing FAPbI3-based PVSCs with and without FcTc2, and FIG. 17B shows the histogram of measured PCE values ​​among 20 devices of FAPbI3-based PVSCs with and without FcTc2. [Figure 18A] 18A and 18B show the SCLC curves of perovskite films with (FIG. 18A) and without (FIG. 18B) FcTc2 based on the electron-only device structure, and FIG. 18C shows the TRPL spectra of perovskite / FcTc2 / C60 and perovskite / C60. [Figure 18B] 18A and 18B show the SCLC curves of perovskite films with (FIG. 18A) and without (FIG. 18B) FcTc2 based on the electron-only device structure, and FIG. 18C shows the TRPL spectra of perovskite / FcTc2 / C60 and perovskite / C60. [Figure 18C] 18A and 18B show the SCLC curves of perovskite films with (FIG. 18A) and without (FIG. 18B) FcTc2 based on the electron-only device structure, and FIG. 18C shows the TRPL spectra of perovskite / FcTc2 / C60 and perovskite / C60. [Figure 19A] FIG. 19 shows the JV curves of the best performing device of the PVSC based on the control device (FIG. 19A) and the device with the FcPh2 interfacial layer (FIG. 19B). [Figure 19B] FIG. 19 shows the JV curves of the best performing device of the PVSC based on the control device (FIG. 19A) and the device with the FcPh2 interfacial layer (FIG. 19B). [Figure 20A] FIG. 20 shows the JV curves of the best performing device of the PVSC based on the control device (FIG. 20A) and the device with the DPC interface layer (FIG. 20B). [Figure 20B] FIG. 20 shows the JV curves of the best performing device of the PVSC based on the control device (FIG. 20A) and the device with the DPC interface layer (FIG. 20B). [Figure 21A] FIG. 21 shows the JV curves of the best performing device of the PVSC based on the control device (FIG. 20A) and the device with the BA interface layer (FIG. 20B). [Figure 21B] FIG. 21 shows the JV curves of the best performing device of the PVSC based on the control device (FIG. 20A) and the device with the BA interface layer (FIG. 20B). [Figure 22A] FIG. 22 shows the UV-visible spectra of FcTc2 in solution (FIG. 22A) and thin film (FIG. 22B) form. [Figure 22B] FIG. 22 shows the UV-visible spectra of FcTc2 in solution (FIG. 22A) and thin film (FIG. 22B) form. [Figure 23A] FIG. 23 shows a density functional theory (DFT) simulation of the interaction between FAPbI3 and FcTc2 molecules. [Figure 23B] FIG. 23 shows a density functional theory (DFT) simulation of the interaction between FAPbI3 and FcTc2 molecules. [Figure 23C] FIG. 23 shows a density functional theory (DFT) simulation of the interaction between FAPbI3 and FcTc2 molecules. [Figure 24] FIG. 24 shows electrostatic potential (ESP) analysis of FcTc2. [Figure 25A] Figure 25 shows: a) surface molecular interactions of functionalized Fc-based compound structures; b) electrostatic potential of Fc-based compounds via DFT simulation; c, d) XPS spectra of elements Pb and I; e) XPS spectra of Fe in different Fc compounds at the perovskite surface; f, g) EFM characterization of phase images of perovskite films with and without Fc compounds, where a bias voltage is applied to the tip (-3 to 3 V, 1.5 V steps) to allow extraction of Coulomb forces; h) phase plots related to the applied bias. [Figure 25B]Figure 25 shows: a) surface molecular interactions of functionalized Fc-based compound structures; b) electrostatic potential of Fc-based compounds via DFT simulation; c, d) XPS spectra of elements Pb and I; e) XPS spectra of Fe in different Fc compounds at the perovskite surface; f, g) EFM characterization of phase images of perovskite films with and without Fc compounds, where a bias voltage is applied to the tip (-3 to 3 V, 1.5 V steps) to allow extraction of Coulomb forces; h) phase plots related to the applied bias. [Figure 25C] Figure 25 shows: a) surface molecular interactions of functionalized Fc-based compound structures; b) electrostatic potential of Fc-based compounds via DFT simulation; c, d) XPS spectra of elements Pb and I; e) XPS spectra of Fe in different Fc compounds at the perovskite surface; f, g) EFM characterization of phase images of perovskite films with and without Fc compounds, where a bias voltage is applied to the tip (-3 to 3 V, 1.5 V steps) to allow extraction of Coulomb forces; h) phase plots related to the applied bias. [Figure 25D] Figure 25 shows: a) surface molecular interactions of functionalized Fc-based compound structures; b) electrostatic potential of Fc-based compounds via DFT simulation; c, d) XPS spectra of elements Pb and I; e) XPS spectra of Fe in different Fc compounds at the perovskite surface; f, g) EFM characterization of phase images of perovskite films with and without Fc compounds, where a bias voltage is applied to the tip (-3 to 3 V, 1.5 V steps) to allow extraction of Coulomb forces; h) phase plots related to the applied bias. [Figure 25E]Figure 25 shows: a) surface molecular interactions of functionalized Fc-based compound structures; b) electrostatic potential of Fc-based compounds via DFT simulation; c, d) XPS spectra of elements Pb and I; e) XPS spectra of Fe in different Fc compounds at the perovskite surface; f, g) EFM characterization of phase images of perovskite films with and without Fc compounds, where a bias voltage is applied to the tip (-3 to 3 V, 1.5 V steps) to allow extraction of Coulomb forces; h) phase plots related to the applied bias. [Figure 25F] Figure 25 shows: a) surface molecular interactions of functionalized Fc-based compound structures; b) electrostatic potential of Fc-based compounds via DFT simulation; c, d) XPS spectra of elements Pb and I; e) XPS spectra of Fe in different Fc compounds at the perovskite surface; f, g) EFM characterization of phase images of perovskite films with and without Fc compounds, where a bias voltage is applied to the tip (-3 to 3 V, 1.5 V steps) to allow extraction of Coulomb forces; h) phase plots related to the applied bias. [Figure 25G] Figure 25 shows: a) surface molecular interactions of functionalized Fc-based compound structures; b) electrostatic potential of Fc-based compounds via DFT simulation; c, d) XPS spectra of elements Pb and I; e) XPS spectra of Fe in different Fc compounds at the perovskite surface; f, g) EFM characterization of phase images of perovskite films with and without Fc compounds, where a bias voltage is applied to the tip (-3 to 3 V, 1.5 V steps) to allow extraction of Coulomb forces; h) phase plots related to the applied bias. [Fig. 25H]Figure 25 shows: a) surface molecular interactions of functionalized Fc-based compound structures; b) electrostatic potential of Fc-based compounds via DFT simulation; c, d) XPS spectra of elements Pb and I; e) XPS spectra of Fe in different Fc compounds at the perovskite surface; f, g) EFM characterization of phase images of perovskite films with and without Fc compounds, where a bias voltage is applied to the tip (-3 to 3 V, 1.5 V steps) to allow extraction of Coulomb forces; h) phase plots related to the applied bias. [Figure 26A] Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 26B] Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 26C]Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 26D] Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 26E] Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 26F]Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 26G] Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Fig. 26H] Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 26I]Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 26J] Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 26K] Figure 26 shows the potential evaluation and carrier dynamics, where a-d show KPFM of surface contact potential difference (CPD) of perovskite films treated with different Fc compounds, e-h show statistics of surface work function of perovskite films, i shows TRPL spectrum of perovskite / ETL films with different Fc compounds, J shows integral fitting value of PL mapping intensity for perovskite / ETL films with different Fc compounds, and k shows statistics of trap filling voltage VTFL and EQE of EL values ​​for perovskite devices with different Fc compounds. [Figure 27A]FIG. 27 shows PV performance, a shows a schematic of the device structure, b shows cross-sectional SEM images of the PSCs, c shows JV curves of the best performing PSCs treated with different Fc compounds, d shows the highest PCE of PSCs treated with different Fc compounds, e shows JV curves of forward and backward scans of the device containing Fc2Tc2, f shows EQE and integrated current density, g shows stabilized power output of Fc2Tc2 treated PSCs, h shows PV parameter statistics for control and Fc2Tc2 treated PSCs. Mask area is 0.0414 cm2. [Figure 27B] FIG. 27 shows PV performance, a shows a schematic of the device structure, b shows cross-sectional SEM images of the PSCs, c shows JV curves of the best performing PSCs treated with different Fc compounds, d shows the highest PCE of PSCs treated with different Fc compounds, e shows JV curves of forward and backward scans of the device containing Fc2Tc2, f shows EQE and integrated current density, g shows stabilized power output of Fc2Tc2 treated PSCs, h shows PV parameter statistics for control and Fc2Tc2 treated PSCs. Mask area is 0.0414 cm2. [Figure 27C] FIG. 27 shows PV performance, a shows a schematic of the device structure, b shows cross-sectional SEM images of the PSCs, c shows JV curves of the best performing PSCs treated with different Fc compounds, d shows the highest PCE of PSCs treated with different Fc compounds, e shows JV curves of forward and backward scans of the device containing Fc2Tc2, f shows EQE and integrated current density, g shows stabilized power output of Fc2Tc2 treated PSCs, h shows PV parameter statistics for control and Fc2Tc2 treated PSCs. Mask area is 0.0414 cm2. [Figure 27D]FIG. 27 shows PV performance, a shows a schematic of the device structure, b shows cross-sectional SEM images of the PSCs, c shows JV curves of the best performing PSCs treated with different Fc compounds, d shows the highest PCE of PSCs treated with different Fc compounds, e shows JV curves of forward and backward scans of the device containing Fc2Tc2, f shows EQE and integrated current density, g shows stabilized power output of Fc2Tc2 treated PSCs, h shows PV parameter statistics for control and Fc2Tc2 treated PSCs. Mask area is 0.0414 cm2. [Figure 27E] FIG. 27 shows PV performance, a shows a schematic of the device structure, b shows cross-sectional SEM images of the PSCs, c shows JV curves of the best performing PSCs treated with different Fc compounds, d shows the highest PCE of PSCs treated with different Fc compounds, e shows JV curves of forward and backward scans of the device containing Fc2Tc2, f shows EQE and integrated current density, g shows stabilized power output of Fc2Tc2 treated PSCs, h shows PV parameter statistics for control and Fc2Tc2 treated PSCs. Mask area is 0.0414 cm2. [Figure 27F] FIG. 27 shows PV performance, a shows a schematic of the device structure, b shows cross-sectional SEM images of the PSCs, c shows JV curves of the best performing PSCs treated with different Fc compounds, d shows the highest PCE of PSCs treated with different Fc compounds, e shows JV curves of forward and backward scans of the device containing Fc2Tc2, f shows EQE and integrated current density, g shows stabilized power output of Fc2Tc2 treated PSCs, h shows PV parameter statistics for control and Fc2Tc2 treated PSCs. Mask area is 0.0414 cm2. [Figure 27G]FIG. 27 shows PV performance, a shows a schematic of the device structure, b shows cross-sectional SEM images of the PSCs, c shows JV curves of the best performing PSCs treated with different Fc compounds, d shows the highest PCE of PSCs treated with different Fc compounds, e shows JV curves of forward and backward scans of the device containing Fc2Tc2, f shows EQE and integrated current density, g shows stabilized power output of Fc2Tc2 treated PSCs, h shows PV parameter statistics for control and Fc2Tc2 treated PSCs. Mask area is 0.0414 cm2. [Fig. 27H] FIG. 27 shows PV performance, a shows a schematic of the device structure, b shows cross-sectional SEM images of the PSCs, c shows JV curves of the best performing PSCs treated with different Fc compounds, d shows the highest PCE of PSCs treated with different Fc compounds, e shows JV curves of forward and backward scans of the device containing Fc2Tc2, f shows EQE and integrated current density, g shows stabilized power output of Fc2Tc2 treated PSCs, h shows PV parameter statistics for control and Fc2Tc2 treated PSCs. Mask area is 0.0414 cm2. [Figure 28A] FIG. 28 shows the PV performance and uniformity of large area devices, a shows the JV curves of the best performing pristine and Fc2Tc2-treated PSCs with a masked area of ​​1.008 cm2. b shows the stabilized output of the Fc2Tc2-treated large area PSCs. The inset is a top-view device image. c shows the statistical distribution of Voc and FF for 20 pristine and target devices. d shows the JV curves of a representative Fc2Tc2-treated PSC measured from five different spots with an open area of ​​0.0414 cm2 selected from the total active area. e shows the statistics of normalized PV parameters and CV values ​​of small areas selected from the large area PSCs. The data were recorded from five separate points in four devices and normalized to the highest value of each parameter. f shows the statistics of normalized PL in perovskite / ETLs with and without Fc2Tc2 treatment. CV is the coefficient of variation. [Figure 28B] FIG. 28 shows the PV performance and uniformity of large area devices, a shows the JV curves of the best performing pristine and Fc2Tc2-treated PSCs with a masked area of ​​1.008 cm2. b shows the stabilized output of the Fc2Tc2-treated large area PSCs. The inset is a top-view device image. c shows the statistical distribution of Voc and FF for 20 pristine and target devices. d shows the JV curves of a representative Fc2Tc2-treated PSC measured from five different spots with an open area of ​​0.0414 cm2 selected from the total active area. e shows the statistics of normalized PV parameters and CV values ​​of small areas selected from the large area PSCs. The data were recorded from five separate points in four devices and normalized to the highest value of each parameter. f shows the statistics of normalized PL in perovskite / ETLs with and without Fc2Tc2 treatment. CV is the coefficient of variation. [Figure 28C] FIG. 28 shows the PV performance and uniformity of large area devices, a shows the JV curves of the best performing pristine and Fc2Tc2-treated PSCs with a masked area of ​​1.008 cm2. b shows the stabilized output of the Fc2Tc2-treated large area PSCs. The inset is a top-view device image. c shows the statistical distribution of Voc and FF for 20 pristine and target devices. d shows the JV curves of a representative Fc2Tc2-treated PSC measured from five different spots with an open area of ​​0.0414 cm2 selected from the total active area. e shows the statistics of normalized PV parameters and CV values ​​of small areas selected from the large area PSCs. The data were recorded from five separate points in four devices and normalized to the highest value of each parameter. f shows the statistics of normalized PL in perovskite / ETLs with and without Fc2Tc2 treatment. CV is the coefficient of variation. [Figure 28D]FIG. 28 shows the PV performance and uniformity of large area devices, a shows the JV curves of the best performing pristine and Fc2Tc2-treated PSCs with a masked area of ​​1.008 cm2. b shows the stabilized output of the Fc2Tc2-treated large area PSCs. The inset is a top-view device image. c shows the statistical distribution of Voc and FF for 20 pristine and target devices. d shows the JV curves of a representative Fc2Tc2-treated PSC measured from five different spots with an open area of ​​0.0414 cm2 selected from the total active area. e shows the statistics of normalized PV parameters and CV values ​​of small areas selected from the large area PSCs. The data were recorded from five separate points in four devices and normalized to the highest value of each parameter. f shows the statistics of normalized PL in perovskite / ETLs with and without Fc2Tc2 treatment. CV is the coefficient of variation. [Figure 28E] FIG. 28 shows the PV performance and uniformity of large area devices, a shows the JV curves of the best performing pristine and Fc2Tc2-treated PSCs with a masked area of ​​1.008 cm2. b shows the stabilized output of the Fc2Tc2-treated large area PSCs. The inset is a top-view device image. c shows the statistical distribution of Voc and FF for 20 pristine and target devices. d shows the JV curves of a representative Fc2Tc2-treated PSC measured from five different spots with an open area of ​​0.0414 cm2 selected from the total active area. e shows the statistics of normalized PV parameters and CV values ​​of small areas selected from the large area PSCs. The data were recorded from five separate points in four devices and normalized to the highest value of each parameter. f shows the statistics of normalized PL in perovskite / ETLs with and without Fc2Tc2 treatment. CV is the coefficient of variation. [Figure 28F]FIG. 28 shows the PV performance and uniformity of large area devices, a shows the JV curves of the best performing pristine and Fc2Tc2-treated PSCs with a masked area of ​​1.008 cm2. b shows the stabilized output of the Fc2Tc2-treated large area PSCs. The inset is a top-view device image. c shows the statistical distribution of Voc and FF for 20 pristine and target devices. d shows the JV curves of a representative Fc2Tc2-treated PSC measured from five different spots with an open area of ​​0.0414 cm2 selected from the total active area. e shows the statistics of normalized PV parameters and CV values ​​of small areas selected from the large area PSCs. The data were recorded from five separate points in four devices and normalized to the highest value of each parameter. f shows the statistics of normalized PL in perovskite / ETLs with and without Fc2Tc2 treatment. CV is the coefficient of variation. [Figure 29A] 29A-E show the JV curves of functionalized ferrocene compounds for perovskite solar cells. [Figure 29B] 29A-E show the JV curves of functionalized ferrocene compounds for perovskite solar cells. [Figure 29C] 29A-E show the JV curves of functionalized ferrocene compounds for perovskite solar cells. [Figure 29D] 29A-E show the JV curves of functionalized ferrocene compounds for perovskite solar cells. [Figure 29E] 29A-E show the JV curves of functionalized ferrocene compounds for perovskite solar cells. [Diagram 30] FIG. 30 shows the efficiency enhancement of large-area and small-area PSCs with regular and inverted structures, as well as the efficiency gap between large-area and small-area PSCs. [Diagram 31] FIG. 31 shows the XPS spectra of elemental Pb in perovskite films containing different Fc compounds. [Diagram 32]FIG. 32 shows the XPS spectra of element I in perovskite films containing different Fc compounds. [Diagram 33] Figure 33 shows the UV-visible absorption spectra of perovskite films containing different Fc compounds. [Figure 34A] FIG. 34 shows AFM images of perovskite films containing different Fc compounds. [Figure 34B] FIG. 34 shows AFM images of perovskite films containing different Fc compounds. [Figure 34C] FIG. 34 shows AFM images of perovskite films containing different Fc compounds. [Fig. 34D] FIG. 34 shows AFM images of perovskite films containing different Fc compounds. [Figure 35A] Figure 35 shows a, c EFM characterization of phase images of perovskite films containing FcTc2 and Fc3Tc2 compounds, where a bias voltage is applied to the tip (-3 to 3 V, steps of 1.5 V) to allow extraction of Coulomb forces, and b, d phase plots of perovskite films containing FcTc2 and Fc3Tc2 compounds relative to the applied bias. [Figure 35B] Figure 35 shows a, c EFM characterization of phase images of perovskite films containing FcTc2 and Fc3Tc2 compounds, where a bias voltage is applied to the tip (-3 to 3 V, steps of 1.5 V) to allow extraction of Coulomb forces, and b, d phase plots of perovskite films containing FcTc2 and Fc3Tc2 compounds relative to the applied bias. [Figure 35C] Figure 35 shows a, c EFM characterization of phase images of perovskite films containing FcTc2 and Fc3Tc2 compounds, where a bias voltage is applied to the tip (-3 to 3 V, steps of 1.5 V) to allow extraction of Coulomb forces, and b, d phase plots of perovskite films containing FcTc2 and Fc3Tc2 compounds relative to the applied bias. [Figure 35D]Figure 35 shows a, c EFM characterization of phase images of perovskite films containing FcTc2 and Fc3Tc2 compounds, where a bias voltage is applied to the tip (-3 to 3 V, steps of 1.5 V) to allow extraction of Coulomb forces, and b, d phase plots of perovskite films containing FcTc2 and Fc3Tc2 compounds relative to the applied bias. [Figure 36A] Figure 36 shows the statistics of the phase angles of pristine perovskite films under different applied bias voltages. [Figure 36B] Figure 36 shows the statistics of the phase angles of pristine perovskite films under different applied bias voltages. [Figure 36C] Figure 36 shows the statistics of the phase angles of pristine perovskite films under different applied bias voltages. [Figure 36D] Figure 36 shows the statistics of the phase angles of pristine perovskite films under different applied bias voltages. [Figure 36E] Figure 36 shows the statistics of the phase angles of pristine perovskite films under different applied bias voltages. [Figure 37A] Figure 37 shows the statistics of the phase angles of the Fc-modified perovskite films under different applied bias voltages. [Figure 37B] Figure 37 shows the statistics of the phase angles of the Fc-modified perovskite films under different applied bias voltages. [Figure 37C] Figure 37 shows the statistics of the phase angles of the Fc-modified perovskite films under different applied bias voltages. [Figure 37D] Figure 37 shows the statistics of the phase angles of the Fc-modified perovskite films under different applied bias voltages. [Figure 37E] Figure 37 shows the statistics of the phase angles of the Fc-modified perovskite films under different applied bias voltages. [Figure 38] FIG. 38 shows the TOF-SIMS plot of the Fc2Tc2 modified perovskite solar cell. [Figure 39] Figure 39 shows the steady-state PL spectra of perovskite films treated with different Fc compounds. [Figure 40A] Figure 40 shows PL mapping of perovskite films with a) control, b) FcTc2, c) Fc2Tc2 and d) Fc3Tc2 modification. [Figure 40B] Figure 40 shows PL mapping of perovskite films with a) control, b) FcTc2, c) Fc2Tc2 and d) Fc3Tc2 modification. [Figure 40C] Figure 40 shows PL mapping of perovskite films with a) control, b) FcTc2, c) Fc2Tc2 and d) Fc3Tc2 modification. [Figure 40D] Figure 40 shows PL mapping of perovskite films with a) control, b) FcTc2, c) Fc2Tc2 and d) Fc3Tc2 modification. [Diagram 41] FIG. 41 shows thickness measurements of perovskite films based on Dektak XTL. [Figure 42A] FIG. 42 shows the SCLC characterization of defect density of pristine and modified perovskite films containing different Fc-based compounds based on an electron-only device (FTO / TiO2 / perovskite / Fc / C6o / BCP / Ag). [Figure 42B] FIG. 42 shows the SCLC characterization of defect density of pristine and modified perovskite films containing different Fc-based compounds based on an electron-only device (FTO / TiO2 / perovskite / Fc / C6o / BCP / Ag). [Figure 42C] FIG. 42 shows the SCLC characterization of defect density of pristine and modified perovskite films containing different Fc-based compounds based on an electron-only device (FTO / TiO2 / perovskite / Fc / C6o / BCP / Ag). [Fig.42D] FIG. 42 shows the SCLC characterization of defect density of pristine and modified perovskite films containing different Fc-based compounds based on an electron-only device (FTO / TiO2 / perovskite / Fc / C6o / BCP / Ag). [Figure 43A] FIG. 43 shows the light-independent open circuit voltage for pristine and Fc-modified PSCs. [Figure 43B]FIG. 43 shows the light-independent open circuit voltage for pristine and Fc-modified PSCs. [Figure 43C] FIG. 43 shows the light-independent open circuit voltage for pristine and Fc-modified PSCs. [Fig. 43D] FIG. 43 shows the light-independent open circuit voltage for pristine and Fc-modified PSCs. [Figure 44A] Figure 44 shows the EL spectra of a) control, b) FcTc2, c) Fc2Tc2 and d) Fc3Tc2 modified perovskite devices under different voltage biases operating as LEDs. [Figure 44B] Figure 44 shows the EL spectra of a) control, b) FcTc2, c) Fc2Tc2 and d) Fc3Tc2 modified perovskite devices under different voltage biases operating as LEDs. [Figure 44C] Figure 44 shows the EL spectra of a) control, b) FcTc2, c) Fc2Tc2 and d) Fc3Tc2 modified perovskite devices under different voltage biases operating as LEDs. [Fig.44D] Figure 44 shows the EL spectra of a) control, b) FcTc2, c) Fc2Tc2 and d) Fc3Tc2 modified perovskite devices under different voltage biases operating as LEDs. [Diagram 45] FIG. 45 shows EL plots of EQE for control, FcTc2-, Fc2Tc2- and Fc3Tc2-treated PSCs. [Diagram 46] FIG. 46 shows the JV curves of the obedient and post-order scans of the initial PSC with the best performance. [Figure 47] FIG. 47 shows the JV curves of the best performing PSCs modified by different concentrations of FC2TC2. [Figure 48] FIG. 48 shows the PCE statistics of PSCs modified with different Fc compounds and varying concentrations. [Figure 49] FIG. 49 shows the high sensitivity EQE of primary and Fc2Tc2-treated PSCs. [Figure 50]FIG. 50 shows the energy loss statistics for control and Fc2Tc2-treated PSCs. [Figure 51] Figure 51 shows long-term operational stability measurements of encapsulated devices under simulated solar illumination of AM1.5G in N2 atmosphere at room temperature. One out of every 70 points is selected as a representative point shown on each curve. [Figure 52A] FIG. 52 shows five-point PL spectra of a) pristine perovskite / ETL film and b) Fc2Tc2-treated perovskite / ETL film. [Figure 52B] FIG. 52 shows five-point PL spectra of a) pristine perovskite / ETL film and b) Fc2Tc2-treated perovskite / ETL film. [Figure 53A] FIG. 53 shows KPFM images and potential distribution of a control membrane at three different sites. [Figure 53B] FIG. 53 shows KPFM images and potential distribution of a control membrane at three different sites. [Figure 53C] FIG. 53 shows KPFM images and potential distribution of a control membrane at three different sites. [Fig. 53D] FIG. 53 shows KPFM images and potential distribution of a control membrane at three different sites. [Figure 53E] FIG. 53 shows KPFM images and potential distribution of a control membrane at three different sites. [Fig. 53F] FIG. 53 shows KPFM images and potential distribution of a control membrane at three different sites. [Figure 54A] FIG. 54 shows KPFM images and potential distribution of Fc2Tc2-treated membranes at three different sites. [Figure 54B] FIG. 54 shows KPFM images and potential distribution of Fc2Tc2-treated membranes at three different sites. [Fig. 54C] FIG. 54 shows KPFM images and potential distribution of Fc2Tc2-treated membranes at three different sites. [Fig. 54D] FIG. 54 shows KPFM images and potential distribution of Fc2Tc2-treated membranes at three different sites. [Figure 54E] FIG. 54 shows KPFM images and potential distribution of Fc2Tc2-treated membranes at three different sites. [Fig. 54F] FIG. 54 shows KPFM images and potential distribution of Fc2Tc2-treated membranes at three different sites. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] With reference to Figure 1A, a "conventional" perovskite photovoltaic cell (also referred to herein as a perovskite solar cell) 100a is described that includes an np or nip junction (electrons are collected at the transparent electrode). With reference to Figure 1B, an "inverted" perovskite photovoltaic cell (also referred to herein as a perovskite solar cell) 100b is described that includes a pn or pin junction (holes are collected at the transparent electrode). In the following discussion of Figure 1 (Figures 1A and 1B), like reference numerals refer to like features.

[0034] Among perovskite solar cells (PVSCs), inverted (pn / pin structure) devices typically exhibit more stable behavior than conventional (np / nip) PVSCs, due in part to the undoped hole transport material and highly crystalline perovskite films. The following description primarily refers to inverted PVSCs, but the beneficial effects of the interfacial layers described herein apply equally to conventional (nip) PVSC structures.

[0035] A transparent substrate 102 is provided. This forms a base or support for the solar cell structure 100. The photovoltaic cell (solar cell 100) may be implemented as a tandem solar cell. For example, the solar cell 100 may be implemented as a tandem perovskite-on-silicon solar cell. The perovskite layer, the electron transport layer and the interface layer may be provided as part of a perovskite cell in this arrangement, which is formed on or built on top of a silicon cell to form the tandem photovoltaic cell (solar cell 100). Visible light 116 (e.g., incident sunlight) enters the solar cell 100 (e.g., solar cell 100a or 100b) through the transparent substrate 102. The substrate 102 may be formed of glass or any other suitable transparent material.

[0036] The solar cell 100 (e.g., solar cell 100a or 100b) includes a perovskite layer 110. In use, the perovskite layer 110 absorbs light incident on the solar cell 100. The term "light absorption" as it relates to the perovskite(s) (and by extension the layer 110 comprising one or more perovskites described above) refers to the role of absorbing light, e.g., visible light 116, to act as a light absorbing material that converts the light 116 into electrical energy. The perovskite-type compound exhibits strong absorption for visible light 116 incident on the solar cell 100, and the band gap of the perovskite semiconductor is such that the desired band gap energy E g can be adapted to improve the efficiency of such solar cells.

[0037] As in a typical solar cell shown in Figure 1, solar radiation or visible light 116 passes through the substrate layer 102 into the active layer 110, where at least a portion of the solar radiation 116 is absorbed by exciting electrons across the semiconductor band gap to enable electricity generation. In particular, electrons are excited from the valence band of the semiconductor across the band gap to the conduction band. The excited electrons enter the conduction band and a corresponding hole (a vacancy or absence of an electron rather than a physical particle within and of itself) remains in the valence band of the semiconductor.

[0038] The asymmetry in the functional layer 110 acts to move the charge carriers (holes and electrons) away from the electron promotion points for collection and current generation, moving excited electrons away from the holes. In the examples described herein, this asymmetry is imparted by a junction in the perovskite layer 110 (e.g., an np or nip junction for the solar cell 100a in FIG. 1A, or a pn or pin junction for the solar cell 100b in FIG. 1B). It will thus be understood that the perovskite layer may include any suitable semiconductor junction. However, the asymmetry in the perovskite layer may be imparted in any other suitable manner.

[0039] In some examples, the perovskite layer 110 may include one or more heterojunctions. A heterojunction may be formed in the perovskite layer 110 by two different undoped perovskite materials. Thus, the perovskites referred to herein may both be undoped semiconductors. Alternatively, the perovskite(s) may be doped by p-type or n-type dopants to form the junction. In other words, they may be doped (throughout and / or at the surface) by at least one dopant material of higher valence than the bulk material (giving n-type doping) and / or by at least one dopant material of lower valence than the bulk material (giving p-type doping). N-type doping tends to increase the n-type character of the semiconductor material, while p-type doping tends to decrease the degree of the natural n-type state (e.g., due to defects). Such doping may be made with any suitable material, including F, Sb, N, Ge, Si, C, In, InO and / or Al. Suitable dopants and doping levels will be apparent to those skilled in the art.

[0040] In some examples, the light absorbing perovskite layer 110 comprises one or more metal halide perovskites. In some examples, the light absorbing layer may comprise two different metal halide perovskites configured to form a semiconductor heterojunction within layer 110. Any perovskite(s) capable of performing the desired light absorption and charge separation functions may be used in the light absorbing layer 110.

[0041] With further reference to the solar cell 100, an electron transport layer, ETL 106, is provided. The ETL (or n-type charge extraction layer) comprises an electron transport material. Any electron transport material known to those skilled in the art may be used. The ETL may comprise or consist of an organic electron transport material, an inorganic electron transport material, or a mixture thereof. Exemplary electron transport materials include organic materials, such as fluorenes, metal oxides, such as TiO2, ZnO, SnO2, SiO2, or ZrO2.

[0042] Fluorene is preferred. Fluorene is a C 60 Fluorene and C 70 Exemplary substituents include any of the known fluorenes, including C 1-12 Alkyl groups include C 1-12 One or more non-adjacent C atoms of the alkyl may be replaced by O, S, CO or COO and optionally substituted phenyl, and the two substituents may be linked to form a monocyclic or polycyclic ring. Exemplary fluorenes include C 60 , PCBM and ICBA.

[0043] The electron transport material may facilitate the flow of electrons from the n-type perovskite, while blocking the movement of holes, and away from the junction in layer 110. Thus, electrons accumulate in the first conductor 104. In use, the first conductor 104 becomes negatively charged due to the accumulation of electrons. When the solar cell is connected to an external load, electrons leave the solar cell 100 via the first conductor 104.

[0044] A hole transport layer, HTL, 112, including or consisting of one or more hole transport materials, may also be provided in the solar cell 100. In the inverted PVSC of Figure 1B, the HTL is located proximal to the transparent substrate (holes are concentrated in the electrode proximal to the substrate, as opposed to the conventional PVSC of Figure 1A). Any hole transport material known to one of skill in the art may be used.

[0045] Exemplary hole-transporting materials include organic hole-transporting materials, inorganic hole-transporting materials, or combinations thereof. Organic hole-transporting materials can be polymeric or non-polymeric. Exemplary polymeric hole-transporting materials include polythiophenes, such as poly(3-hexylthiophene) (P3HT); poly(arylamines), such as PTTA; and doped PEDOT, such as PEDOT:PSS. Exemplary non-polymeric organic hole-transporting materials are compounds containing one or more arylamine groups, such as spiro-OMeTAD. Exemplary inorganic hole-transporting materials include copper-based materials (e.g., CuO x , CuSCN, CuI, etc.), nickel-based materials (e.g., NiO x ), two-dimensional layered materials such as chalcogenides (e.g., MoS2, WS2, etc.). The hole transport material encourages the flow of holes from the p-type perovskite away from the junction in layer 110 while blocking the movement of electrons. Thus, holes accumulate in second conductor 114. In use, second conductor 114 becomes positively charged due to the accumulation of holes.

[0046] In a conventional PVSC, the first conductor 104 may be a transparent conductive material. In some examples, the first conductor 104 is a transparent conductive film (TCF). In some examples, the TCF is a transparent conductive oxide (TCO) layer. In some examples, the TCO layer includes indium tin oxide (ITO), fluorine-doped tin oxide (FTO) or doped tin oxide. The second conductor 114 may be formed of any suitable conductive material, such as Ag, Au, Cu, etc. In an inverted PVSC, the second conductor 114 may be any transparent conductive material (since in the inverted structure, this is the contact that is placed on the transparent substrate 102), such as a transparent conductive film, or more specifically, a TCO. The first conductor 104 may be formed of any suitable conductive material, such as Ag, Au, Cu, Al, etc. The first and second conductors or contacts are for connection to an external load.

[0047] In previous PVSCs, the functional or active perovskite layer 110 was sandwiched between the HTL 112 and the ETL 106. In other words, charge transport layers are deposited on the top and bottom sides of the perovskite active layer, respectively. Charge carriers are extracted at the HTL / perovskite and perovskite / ETL interfaces and collected through conductors / contacts, respectively. During this process, carrier charges may be subject to recombination, for example, due to any interface defects and associated specific charge distributions.

[0048] Interface recombination arises from charge dynamics at the interface, including charge extraction, charge transfer, and charge recombination. Imperfect interface structures and electronic mismatches usually act as energy barriers for charge transport and charge recombination. Furthermore, defects at the surface and interfaces of polycrystalline perovskite films are mostly either positively or negatively charged. Trap states at the perovskite surface and interfaces can lead to charge accumulation and recombination losses in devices.

[0049] It has been found that the performance of the perovskite solar cells described herein can be improved when an interfacial layer 108 comprising an interfacial compound as described herein is provided between the electron transport layer 106 and the perovskite layer 110. Such a layer can suppress defects at the perovskite surface and can also minimize non-radiative coupling losses at the interface. In this way, the interfacial layer 108 improves the extraction of electrons at the perovskite interface, increasing the efficiency of the solar cell and improving the stability of the solar cell 100.

[0050] The interfacial layer 108 directly interfaces with the perovskite layer 110. In other words, the interfacial layer 108 and the perovskite layer are in direct contact. The interfacial layer 108 may be deposited directly onto the active perovskite layer 110 as described below, or may be otherwise formed. The interfacial layer 108 is described in more detail below.

[0051] One or more additional layers (not shown) may be provided in the solar cell structure 100. For example, one or more optional hole blocking layers may be provided between the ETL 106 and the contact 104, and / or between the interfacial layer 108 and the ETL 106. Similarly, another optional electron blocking layer may be provided between the HTL 112 and the contact 114, and / or between the perovskite layer 110 and the HTL 112. Any other layers may be provided in the solar cell 100 as desired.

[0052] Multiple photovoltaic cells 100a, 100b can be connected together in series and encapsulated to form a photovoltaic module (not shown). Photovoltaic modules can be used singly or multiple can be connected in series and / or in parallel into a photovoltaic array, depending on the power required by a particular input or application.

[0053] interfacial layer The interfacial layer comprises or consists of a metallocene substituted with at least one substituent containing an O, S, N or P atom having a lone pair of electrons.

[0054] The inventors have surprisingly found that the presence of such an interfacial layer can improve the stability and performance of perovskite solar cells. Furthermore, the inventors have found that these benefits are achievable over large area cells, for example up to 30cm x 30cm, for example up to 15cm x 15cm. Optionally, the cell area is at least 1 x 1cm.

[0055] Without wishing to be bound by any theory, it is believed that the flexibility of the metallocene around the metal-aromatic bond may relieve stress between the electron transport layer and the perovskite layer.

[0056] Furthermore, without wishing to be bound by any theory, it is believed that the lone pair of electrons of the O, S, N or P groups can bond to uncoordinated metal defects, e.g., Pb defects, on the perovskite surface.

[0057] The metallocene is preferably a compound of formula (I): [Metallocene]p (I) During the ceremony: The metallocene is a compound having two aromatic or heteroaromatic groups Ar 1 a metallocene group comprising a metal bonded to p is at least 1, optionally 1, 2 or 3; At least one metallocene has at least one substituent R 1 is replaced by R 1 is a group containing an O, S, N or P atom: It is.

[0058] Optionally, the compound of formula (I) has formula (Ia): [ka] During the ceremony: M is a metal ion; Ar 1 is, at each occurrence, a monocyclic or polycyclic aromatic or heteroaromatic group; M and two Ar 1 the groups form a metallocene; At least one Ar 1 But there is at least one R 1 is replaced by R 1 is a group containing an O, S, N or P atom; R 2 is a group that satisfies the valence of M; q is 0 or a positive integer, preferably 0 or 2; R 3 is, at each occurrence, independently H or a substituent; p is at least 1; has.

[0059] Exemplary Ar 1 Groups include, without limitation, C4-C8 aromatic groups, i.e., cyclobutadiene, cyclopentadienyl, benzene, cyclopentatrienyl, or cyclooctatetracene; and C5 heteroaromatic groups, such as pyrrole, each of which may be unfused or fused to one or more further rings, preferably one or more benzene rings. Exemplary fused groups Ar 1 Examples include benzocyclopentadienyl and fluorenyl.

[0060] Metallocenes are those that contain two cyclopentadienyl groups, Ar 1 Preferably, the metal M is bonded to Ar 1 may consist of a cyclopentadienyl group or the cyclopentadienyl may be fused to one or more further rings, preferably one or more aromatic rings, e.g., one or more benzene rings, as in benzocyclopentadienyl or fluorenyl.

[0061] M is Fe2+ , Co 2+ , Cr 2+ , Ni 2+ or V 2+ , preferably Fe 2+ For each of these compounds, q is 0.

[0062] M may be Zr or Ti. For each of these compounds, q is 2 and R 2 may be any suitable group capable of bonding to Zr or Ti, for example in a dihalogenated metallocene, such as methyl, ammonia, dialkylamine, phosphine, CO, or a halogen, such as Cl.

[0063] The above or each metallocene has two Ar 1 The group is a divalent group, e.g., C 1-6 Alkylene or formula Si(R 3 )2 groups: 3 But for each event, C 1-12 Hydrocarbyl groups, such as C 1-12 -M may be linked other than through -M by -alkyl or phenyl. It will therefore be understood that the compounds of formula (I) include ansa-metallocenes.

[0064] In a preferred embodiment, M and Ar 1 forms ferrocene, i.e. M is Fe; each Ar 1 is cyclopentadienyl; and y is 0.

[0065] Preferably, R 1 Ar 1 is the only substituent on the group.

[0066] Preferably, p is 1, 2 or 3, more preferably 1.

[0067] The compound of formula (Ia) may be represented by formula (Ib), (Ic) or (Id): [ka] wherein t1 is 0, 1 or 2, preferably 0 or 1; t2 is 0 or 1, preferably 1; and at least one of t1 and / or t2 is at least 1;

[0068] In some embodiments, R 1 is a group of formula (II): -AB (II) In the formula, A is a divalent group containing O, S, N or P; B is H, C 1-12 alkyl, optionally substituted aryl or optionally substituted heteroaryl;

[0069] Group A may include any group capable of binding to Pb. Exemplary groups A include, without limitation, ethers, thioethers, amines, phosphines, phosphoryl ethers, carbonates, carbamates, carboxylates, amides, thioamides, phosphonamides, thiocarboxylates, aminocarboxylates, and phosphocarboxylates. R1 may include only one group A. R 1 may contain more than one group A.

[0070] Exemplary groups A include those of formulae (III) and (IV): -(R 5 ) f -Z-(R 5 )g-(III) -(R 6 O) j - (IV) During the ceremony: R 5 is, at each occurrence, independently a hydrocarbon group; f and g are each independently 0 or 1; R 6 But, C 1-4 an alkylene group, preferably ethylene; j is 1 to 10; Z is O, S, COO, C(=S)O, C(=O)S, CONR 4 , CSNR 4 , OC(=O)O, OC(=O)NR 4 ,OC(=O)PR 4、 NR 4 , P.R. 4 ,-OP(=O)(OR 4 )-O-, or -NR 4 -P(=O)(NR 4 2)-NR 4 - and R 4 is H, optionally substituted C 1-12 alkyl or optionally substituted phenyl; The following groups are included:

[0071] Hydrocarbon group R 5 is C 1-6 alkylene; optionally substituted phenylene; and C 1-6 It is preferably selected from alkylene-phenylene.

[0072] R 5 The phenylene group of the group may be unsubstituted and is 1-6 It may be substituted by one or more substituents selected from alkyl.

[0073] R 5 C 1-6 When alkylene-phenylene, the group Z may be attached to either the alkylene or the phenylene group.

[0074] Particularly preferred groups A are -OC(=O)-, which may be linked to the metallocene via the O atom or via a C atom, preferably via an O atom.

[0075] B is preferably an optionally substituted aryl or heteroaryl, more preferably phenyl or a 5-membered heteroaromatic ring containing one or more of N, S and O ring atoms, such as furan, thiophene, pyrrole, imidazole and oxazole. Thiophene is particularly preferred.

[0076] Optional substituents of the optionally substituted alkyl or alkylene groups described anywhere in this specification include F, Cl, OR 4 and N.R. 4 2, where R 4 is C 1-6 It is an alkyl.

[0077] The substituent R of formula (Ia) may include, but is not limited to, 3 Optional substituents of any optionally substituted aromatic or heteroaromatic group described anywhere in this specification, including F, Cl, CN, NO, C 1-6 alkyl, where one or more H atoms are F, OR 4 and N.R. 4 2, where R 4 is C 1-6 It is an alkyl.

[0078] Without wishing to be bound by any theory, the electron-rich heteroaryl group B may form a coordinate bond with the Pb of the perovskite. This coordinate bond may be in addition to or instead of the bond of group A. Thus, in some embodiments, R 1 may be a 5-membered heteroaromatic group of formula B above.

[0079] Referring to Figure 2, structures of example compounds for the interfacial layer 108 are shown. In one embodiment, the interfacial layer 108 includes ferrocenyl-bis-thiophene-2-carboxylate (FcTc2) as an interfacial functionalization material that improves the efficiency and stability of the PVSC. Ultraviolet-visible (UV-vis) absorption spectroscopy of FcTc2 in solution and thin film form is provided in Figures 22A and 22B, respectively.

[0080] Perovskite A perovskite may be any material with a CatBX3 crystal structure (commonly referred to as a perovskite structure, "ABX3" structure), where Cat and B are cations and × is an anion. B is preferably Pb or Sn.

[0081] The perovskite is preferably of formula CatPbX3 or CatSnX3, where Cat is a metal cation, an organic cation or a combination thereof, and X is selected from at least one of I, Br and Cl.

[0082] Exemplary groups Cat include alkali metal cations, preferably Cs; ammonium cations, such as methylammonium; and amidinium ions, such as formamidinium.

[0083] Preferably, X comprises two of I, Br and Cl.

[0084] Preferably, Cat includes both metal and organic cations.

[0085] Preferably, Cat comprises two different organic cations.

[0086] Examples of perovskites suitable for use as the light absorbing layer include: ammonium trihaloplumbates, such as CH3NH3PbI3, CH3NH3PbCl3, CH3NH3PbF3 and CH3NH3PbBr3; 3-x [Hal2] xmixed halide ammonium trihaloplumbate perovskites according to the general formula (RNH3)BX3, where [Hal1] and [Hal2] are independently selected from among F, Cl, Br and I, with the proviso that [Hal1] and [Hal2] are not identical, and 0<×<3, preferably × is an integer (e.g., 1, 2 or 3, preferably 1 or 2); CsSnX3 perovskites, where × is selected from among F, Cl, Br and I, preferably I; organometallic trihalide perovskites according to the general formula (RNH3)BX3, where R is CH3, C n H 2n or C n H 2n+1 where n is an integer in the range of 2≦n≦10, preferably 2≦n≦5, for example, n=2, n=3, or n=4, most preferably n=2 or n=3, X is a halogen (F, I, Br, or Cl), preferably I, Br, or Cl, and B is Pb or Sn); and combinations thereof. In some examples, Cs x (FA y MA 1-y ) 1-x Pb(I z Br 1-z )3, where perovskite compositions with x=(0-0.95), y=(0-1), z=(0-1) are used, where MA and FA represent methylammonium and formamidinium, respectively.

[0087] Formation of a photovoltaic cell The photovoltaic cells described herein may be formed by any method known to those skilled in the art. Preferably, the perovskite layer and the interfacial layer are formed by depositing a solution containing a perovskite and a solution containing a metallocene, respectively. Suitable solvents for the deposition of the perovskite layer include polar solvents, such as DMF and DMSO. Preferably, the solvent for the deposition of the metallocene is a chlorinated alkane, such as chloroform; and unsubstituted or C 1-6 Alkyl, C 1-6benzene substituted with one or more substituents selected from alkoxy and chlorine, for example dichlorobenzene;

[0088] The solution may be deposited by any method known to those skilled in the art, such as spin-coating, dip-coating, slot-die coating, doctor blade coating and bar coating. EXAMPLES

[0089] The chemistries used herein include: ·Perovskite precursors, cesium iodide (CsI), formamidinium iodide (FAI), methylammonium chloride (MACl), and methylammonium bromide (MABr), were purchased from Dysol (Australia). · Lead iodide (PbI2) and lead bromide (PbBr2) purchased from TCI (Japan). ·C60, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) (Mn 6,000-15,000), methylammonium chloride (MACl) and bathocuproine (BCP, purity 99.9%) were purchased from Xi'an Polymer Light Technology Corporation (China). Copper(I) thiophene-2-carboxylate (CuTC) was purchased from Sigma-Aldrich. · Solvents including dimethylformamide (DMF), dimethyl sulfoxide (DMSO), isopropanol (IPA) and chlorobenzene (CB) were purchased from J&K (China) and used upon receipt. Acetonitrile (MeCN), dichloromethane (DCM), and hexane were purchased from Sigma-Aldrich and used upon receipt. High purity silver was purchased from a commercial source. ITO (15Ω sq -1 ) patterned glass substrates were received from Mishi Tech. Co., Ltd. (China).

[0090] FcTc2-Synthesis 1 A solution of FcI2 (1.0-2.50 mmol), copper thiophene carboxylate (3.2-9.5 mmol) and 9,10-dihydroanthracene (1.5-5.5 mmol) in MeCN was stirred at 50-90 °C for 1-5 days. After cooling to room temperature, DCM was added and the green-blue reaction mixture was filtered over Celite. The solvent was removed and the crude mixture was dissolved in hexane and passed through a silica pad (approximately 5 cm) and the desired product was eluted in 50% DCM in hexane. After solvent removal, FcTc2 was obtained as a yellow solid.

[0091] FcTc2-Synthesis 2 A solution of FcI2 (0.70 g, 1.60 mmol), copper thiophene carboxylate (1.2 g, 6.32 mmol) and 9,10-dihydroanthracene (0.60 g, 3.33 mmol) in MeCN (30 mL) was stirred at 80° C. for 2 days. After cooling to room temperature, DCM (50 mL) was added and the green-blue reaction mixture was filtered over Celite. The solvent was removed and the crude mixture was dissolved in hexane and passed through a silica pad (approximately 5 cm) and the desired product was eluted in 50% DCM in hexane. After solvent removal, FcTc2 was obtained as a yellow solid (0.17 g, 0.38 mmol, 24%). 1 H NMR(400MHz,CDCl3,298K):δ(ppm) 7.78(dd,J=3.7,1.3Hz,2H,thio-H),7.56(dd,J=5.0,1.3Hz,2H,thio-H),7.06(dt,J=5.0 ,3.7Hz,2H,thio-H),4.68(t,J=2.0Hz,4H,(CpTc)mH),4.10(t,J=2.0Hz,4H,(CpTc)oH). 13 C{ 1H} NMR (100 MHz, CDCl3, 298 K): δ (ppm) 160.3 (2C, C=O), 134.2 (2C, thioCH), 133.3 (2C, thioC-CO2Fc), 133.2 (2C, thioCH), 128.0 (2C, thioCH), 116.6 (2C, CpC-O), 64.8 (4C, (CpTc)oCH), 62.2 (4C, (CpTc)mCH). MS ES+: m / z 437.9677 (calculated for [M]+: 437.9683).

[0092] Fc2Tc2-Synthesis The structure of Fc2Tc2 is shown in FIG.

[0093] Ferrocenyl-bis-thiophene-2-carboxylate (FcTc2) was synthesized by a previously reported route (Z. Li, B. Li, X. Wu, SA Sheppard, S. Zhang, D. Gao, NJ Long and Z. Zhu, Science, 2022, 376, 416-420).

[0094] A solution of Fc2I2 (0.50 g, 0.80 mmol) (previously reported in MS Inkpen, S. Scheerer, M. Linseis, AJP White, RF Winter, T. Albrecht and NJ Long, Nat. Chem., 2016, 8, 825-830) and 9,10-dihydroanthracene (0.43 g, 2.41 mmol) in MeCN (100 mL) was sparged with nitrogen for 1 h, after which CuTc (1.53 g, 8.04 mmol) was added. The green-brown reaction mixture was stirred at 80° C. for 2 days. The solvent was then removed and the mixture was filtered over Celite in DCM. The crude mixture was then dissolved in hexane and purified by silica plug (hexane → hexane / DCM (1:1) to give Fc2Tc2 (60 mg, 0.10 mmol, 14%). 1H NMR(400MHz,CDCl3,298K):δ(ppm) 7.76(dd,J=3.8,1.3Hz,1H,thio-H),7.59(dd,J=5.0,1.3Hz,1H,thio-H),7.11(dd,J=5.0,3.8Hz,1H,thio-H),4.44(t,J=1.9H z,4H,(Cp-Cp)mH),4.39(t,J=2.0Hz,4H,(CpTc)mH),4.16(t,J=1.9Hz,4H,(Cp-Cp)oH),3.81(t,J=2.0Hz,4H,(CpTc)oH). 13 C{ 1 H} NMR (100 MHz, CDCl3, 298 K): δ (ppm) 160.4 (2C, C=O), 134.2 (2C, thioCH), 133.5 (2C, thioC-CO2Fc), 133.0 (2C, thioCH), 127.9 (2C, thioCH), 116.3 (2C, CpC-O), 84.4 (2C, CpC-CCp), 69.2 (4C, (Cp-Cp)oCH), 67.7 (4C, (Cp-Cp)mCH), 64.5 (4C, (CpTc)oCH), 62.0 (4C, (CpTc)mCH). MS ES+: m / z 621.9653 (calculated for [M]+: 621.9658).

[0095] Fc3Tc2-synthesis The structure of Fc3Tc2 is shown in FIG.

[0096] MeCN (100 mL) was added to Fc3I2 (0.60 g, 0.74 mmol) (previously reported in MS Inkpen, S. Scheerer, M. Linseis, AJP White, RF Winter, T. Albrecht and NJ Long, Nat. Chem., 2016, 8, 825-830), CuTc (0.30 g, 1.58 mmol) and 9,10 dihydroanthracene (0.20 g, 1.11 mmol). The green-blue reaction mixture was stirred at 80° C. for 2 days. The solvent was then removed and the mixture was filtered in DCM over Celite. The crude mixture was then purified by column chromatography on alumina (V), where Fc3Tc2 (20 mg, 0.03 mmol) was eluted in 40% DCM in hexane. 1 H NMR(400MHz,CDCl3,298K):δ(ppm) 7.73(dd,J=3.7,1.3Hz,2H,thio-H),7.58(dd,J=5.0,1.3Hz,2H,thio-H),7.11(dt,J=5.0,3.7Hz,2H,thio-H),4.34(pseudo-t,J=2.0H z,4H,(CpTc)mH),4.29(Pseudo-t,4H,J=1.8Hz,(Cp-Cp)oH),4.21(Pseudo-t,J=1.8Hz,4H,(Cp-Cp)oH),4.06(Pseudo-t,J=1.8Hz,4H,(Cp Cp)m H),3.89(pseudo-t,J=1.8Hz,4H,(Cp-Cp)mH),3.77(t,J=2.0Hz,4H,(CpTc)oH). 13 C{ 1H} NMR(100MHz,CDCl3,298K):δ(ppm) 160.3(2C,C=O),134.0(2C,ThioCH),133.3(2C,ThioC-CO2Fc),132.8(2C,ThioCH),127.8(2C,ThioCH),116.2(2C,CpC-O),85.3(4C,CpC-CCp),69.2 (4C,(Cp-Cp)mCH),69.0(4C,(Cp-Cp)oCH),67.5(4C,(Cp-Cp)mCH),67.3(4C,(Cp-Cp)oCH),64.4(4C,(CpTc)oCH),61.8(4C,(CpTc)mCH).MS ES+:m / z 805.9641([M]+calculated value:805.9634).

[0097] Iodoferrocene To a solution of ferrocene (21.3 g, 114 mmol, 1 equiv.) in dry, degassed hexane (200 mL) was added tetramethylethylenediamine (TMEDA) (37.7 mL, 251 mmol, 2.2 equiv.) and the mixture was cooled to 0° C. To the cold solution was added a bottle of nBuLi (2.5 M in hexane, 100 mL, 2.2 equiv.) via cannula and the mixture was allowed to slowly warm to room temperature and stirred overnight. The solution was cooled to −78° C. and a separate solution of iodine (43.5 g, 171 mmol, 1.5 equiv.) was prepared in diethyl ether (250 mL) which was then added to the cold solution via cannula. The mixture was brought to 0° C., water was added (100 mL), and then filtered over sand. The resulting filtrate was washed with brine (3×300 mL), dried over MgSO4, and the solvent was then removed in vacuo to give a dark red slurry. The monoferrocene, biferrocene, and triferrocene products were separated using column chromatography (silica, hexane / toluene (6:4)). The monoferrocene fraction was dissolved in hexane and washed (10×0.5 M FeCl3 (aq)) to remove ferrocene and iodoferrocene. The organic phase was then washed with water until no colorless residue was observed, then dried (MgSO4), and the solvent was removed to give 1,1′-diiodoferrocene (FcI2)-CB597F1 (2.73 g, 6.25 mmol, 6%). The biferrocene fraction was dissolved in DCM and washed (5×0.2 M FeCl3 (aq)) to remove biferrocene and monoiodobiferrocene. The organic phase was then washed with water until no colorless residue was observed, then dried (MgSO4) and the solvent removed to give diiodobiferrocene (Fc2I2)-CB597F4+5 (1.09 g, 1.75 mmol, 2%). [ka] CB597F1 1H NMR(400MHz,CDCl3,δ(ppm)):4.37(t,4H,CpH,3JHH=1.9Hz),4.18(t,4H,CpH,3JHH=1.9Hz).13C NMR (101MHz, CDCl3, δ(ppm)): 77.7 (4C, CpC), 72.4 (4C, CpC), 40.4 (2C, CI). HR-MS (ESI+): Calculated value: 437.8065, Actual value: 437.8054. [ka] CB597F4+F5 1H NMR (400 MHz, CDCl3, δ (ppm)): 4.36 (pseudo t, 4H, CpH), 4.24 (pseudo t, 4H, CpH), 4.16 (pseudo t, 4H, CpH), 3.98 (pseudo t, 4H, CpH).13C NMR (101 MHz, CDCl3, δ (ppm)): 84.8 (2C, CpC), 75.9 (2C, CpC), 71.1 (4C, CpC), 70.2 (4H, CpC), 69.7 (4H, CpC), 40.9 (2C, CI).HR-MS (ESI+): calculated: 621.8040, found: 621.8026 (some tripherrocene from mass spectrum but no evidence in NMR).

[0098] Ferrocene thiocarboxylate A solution of 1,1'-diiodoferrocene (CB597F1) (721 mg, 1.60 mmol, 1 equiv) was prepared in lab grade acetonitrile (30 mL) and degassed for 10 min. The mixture was then heated to 80° C. followed by copper(II) thiophene carboxylate (1.24 g, 6.32 mmol, 3.95 equiv) and 9,10-dihydroanthracene (620 mg, 3.33 mmol, 2 equiv) and left overnight. After 24 h, the mixture showed no diiodoferrocene by 1H NMR, so DCM (50 mL) was added and the green solution was allowed to cool to room temperature. The solution was filtered through Celite and purified using column chromatography (silica, hexane → hexane / DCM (1:1)) to give the products ferrocene thiophene carboxylate (FcTc)-CB598F2 (29 mg, 0.091 mmol, 6%) and ferrocene bis(thiophene carboxylate) (FcTc2)-598F3 (109 mg, 0.249 mmol, 16%) as respective fractions. [ka] CB598F2 1H NMR(400MHz,CDCl3,δ(ppm)):7.89(dd,1H,CH,JHH=3.8Hz,1.3Hz),7.63(dd,1H,CH,JHH=5.0Hz,1.3Hz),7.16( dd,1H,CH,JHH=5.0Hz,3.8Hz),4.56(t,2H,CpH,3JHH=2.0Hz),4.26(s,5H,CpH),4.00(t,2H,CpH,3JHH=2.0Hz). [ka] CB598F3 1H NMR(400MHz,CDCl3,δ(ppm)):7.78(d,2H,CH,JHH=3.7Hz),7.56(d,2H,CH,JHH=5.0Hz),7.06(t,2H,CH,JHH=4.3Hz),4.68(pseudo t,4H,CpH),4.10(pseudo t,2H,CpH).

[0099] Carboxaldehyde Ferrocene To a suspension of ferrocene (5.0 g, 27 mmol, 1.0 equiv) in diethyl ether (60 mL) was added TMEDA (10.1 mL, 67.5 mmol, 2.5 equiv) and the resulting solution was cooled to -78 °C. To the cold solution was added nBuLi (26 mL, 64.8 mmol, 2.4 equiv) and the resulting solution was allowed to warm to room temperature and stirred overnight. The solution was cooled again to -78 °C, dimethylformamide (6.27 mL, 81 mmol, 3.0 equiv) was added and the color of the solution became darker. Hydrochloric acid (2.5 M, 205 mL) was added and diethyl ether was removed in vacuo. The product was extracted in DCM (100 mL x 4), washed (1 x 2.5 M HCl; 1 x H2O), dried (Na2SO4) and the solvent was removed in vacuo. The monocarboxylate and dicarboxylate products were separated using column chromatography (silica, hexane / ethyl acetate (1:1→1:3)) to give carboxaldehyde ferrocene CB599F2 (174 mg, 0.812 mmol, 3%) and 1,1′-dicarboxaldehyde ferrocene CB599F3 (4.60 g, 19.0 mmol, 71%). [ka]

[0100] CB599F2 1H NMR(400MHz,CDCl3,δ(ppm)):9.96(s,1H,HC=O),4.80(pseudo t,2H,CpH),4.61(pseudo t,2H,CpH),4.28(s,5H,CpH).13C NMR (101MHz, CDCl3, δ(ppm)): 193.7 (C=O), 73.4 (CpC), 69.8 (CpC). HR-MS (ESI+): Calculated value: 215.0159, Actual value: 215.0168. [ka] CB599F3 1H NMR(400MHz,CDCl3,δ(ppm)):9.94(s,2H,HC=O),4.88(pseudo t,4H,CpH),4.67(pseudo t,4H,CpH).13C NMR (101MHz, CDCl3, δ(ppm)): 193.0 (C=O), 80.4 (CpC), 74.3 (CpC), 71.0 (CpC). HR-MS (ESI+): Calculated value: 243.0108, Actual value: 243.0102.

[0101] Thiophenylferrocene one permutation preference To a suspension of aluminum trichloride (717 mg, 5.38 mmol, 2.0 equiv) in DCM (15 mL) was added 2-thiophenecarbonyl chloride (575 μL, 5.38 mmol, 2.0 equiv), followed by ferrocene (500 mg, 2.69 mmol, 1.0 equiv), turning the orange solution deep blue. After stirring at room temperature for 1 h, the mixture was poured onto ice and stirred for 30 min until completely melted. NaOH (aqueous 25%) was added until neutralization was achieved, then the product was extracted in DCM (3×75 mL), dried (Na2SO4) and the solvent removed in vacuo to give a dark red oil. Purification was achieved using column chromatography (silica, hexane / ethyl acetate (95:5→50:50 gradient) to give (thiophenyl)ferrocene CB601F1 (569 mg, 1.92 mmol, 71%) and 1,1′-bis(thiophenyl)ferrocene (2a) CB601F2 (combined with CB604F3-F4), which was purified once more to give 137 mg of product (CB601+604) (69 g, 0.17 mmol, 6%).

[0102] two-substitution preference To a suspension of aluminum trichloride (3.58 g, 26.9 mmol, 5.0 equiv) in DCM (40 mL) was added 2-thiophenecarbonyl chloride (2.88 mL, 26.9 mmol, 5.0 equiv), followed by ferrocene (1 g, 5.38 mmol, 1.0 equiv), turning the orange solution deep blue. After stirring overnight at room temperature, the mixture was poured onto ice and stirred for 30 min until completely melted. NaOH (aqueous 25%) was added until neutralization was achieved, then the product was extracted in DCM (3 x 75 mL), dried (Na2SO4) and the solvent removed in vacuo to give a dark red oil. Purification was achieved using column chromatography (silica, hexane / ethyl acetate (95:5 to 50:50 gradient) to give 1,1'-bis(thiophenyl)ferrocene (2a) CB608F5 (1.20 g, 2.95 mmol, 55%). CB608F5 could benefit from further purification - another column. [ka] CB601F1 1H NMR(400MHz,CDCl3,δ(ppm)):7.93(dd,1H,ArH,JHH=3.8Hz,1.2Hz),7.62(dd,1H,ArH,JHH=4.9Hz,1.2Hz ),7.16(m,1H,ArH),5.03(t,2H,CpH,3JHH=2.0Hz),4.60(t,2H,CpH,3JHH=2.0Hz),4.23(s,5H,CpH).13C NMR (126MHz, CDCl3, δ(ppm)): 189.7(C=O), 167.0((O=C)C), 131.9(ArC), 131.8(ArC), 127.8(ArC), 72.5(CpC), 71.1(CpC), 70.5(CpC).HR-MS (ESI+): calcd: 297.0033, found: 297.0037. [ka] CB601F2 1H NMR(400MHz,CDCl3,δ(ppm)):7.84(d,2H,ArH,JHH=3.8Hz),7.63(d,2H,ArH,JHH= 4.9Hz),7.13(t,2H,ArH,JHH=4.3Hz),5.06(pseudo t,4H,CpH),4.60(pseudo t,4H,CpH).13C NMR(101MHz,CDCl3,δ(ppm)):188.4(C=O),143.9(ArC),132.7(ArC),132.2(ArC),128.0 (ArC),80.5(CpC),74.8(CpC),72.8(CpC).HR-MS(ESI+): Calculated value: 406.9848, Actual value: 406.9863.

[0103] (Frill)ferrocene To a suspension of aluminum trichloride (1.79 g, 13.44 mmol, 5.0 equiv) in DCM (20 mL) was added 2-furoyl chloride (1.33 mL, 13.44 mmol, 5.0 equiv), followed by ferrocene (500 mg, 2.69 mmol, 1.0 equiv), turning the orange solution deep blue. After stirring overnight at room temperature, the mixture was poured onto ice and stirred for 30 min until completely melted. NaOH (aqueous 25%) was added until neutralization was achieved, then the product was extracted in DCM (3×75 mL), dried (Na2SO4) and the solvent removed in vacuo to give a dark red oil. Purification was achieved using column chromatography (silica, hexane / ethyl acetate (95:5 to 50:50 gradient) to give 1,3-bis(furyl)ferrocene CB605F3 (90 mg, 0.32 mmol, 12%) and 1,1′-bis(furyl)ferrocene (2b) CB605F5 (198 mg, 0.53 mmol, 20%). Could benefit from an additional column, some impurities were present. [ka] CB605F3 1H NMR (400 MHz, CDCl3, δ (ppm)): 7.76 (s, 1H, ArH), 7.65 (dd, 2H, ArH, JHH = 5.8 Hz, 3.7 Hz), 7.40 (d, 1H, ArH, JHH = 3.7 Hz), 6.69 (s, 1H, ArH), 5.28 (t, 1H, CpH, JHH = 2.0 Hz), 4.71 (t, 2H, CpH, JHH = 2.0 Hz), 4.23 (s, 5H, CpH). 13C NMR (101 MHz, CDCl3, δ (ppm)): 147.3 (ArC), 120.4 (ArC), 120.3 (ArC), 117.0 (ArC), 113.0 (ArC), 73.5 (CpC), 71.3 (CpC), 70.6 (CpC). HR-MS (ESI+): Calculated value: 375.0320, Measured value: 375.0324.

Chem.

[0104] (Benzoyl)ferrocene To a suspension of aluminum trichloride (1.79 g, 13.44 mmol, 5.0 equiv.) in DCM (20 mL) was added benzoyl chloride (1.56 mL, 13.44 mmol, 5.0 equiv.), followed by ferrocene (500 mg, 2.69 mmol, 1.0 equiv.), turning the orange solution deep blue. After stirring at room temperature overnight, the mixture was poured onto ice and stirred for 30 min until completely melted. NaOH (aqueous 25%) was added until neutralization was achieved, then the product was extracted in DCM (3×75 mL), dried (Na2SO4), and the solvent removed in vacuo to give a dark red oil. Purification was achieved using column chromatography (silica, hexane / ethyl acetate (95:5→50:50 gradient) to give 1,1′-bis(benzoyl)ferrocene (2d) CB606F3 (745 mg, 1.89 mmol, 70%). [ka] CB606F5 1H NMR(400MHz,CDCl3,δ(ppm)):7.78(d,4H,ArH,JHH=7.6Hz),7.54(t,2H,ArH,JHH= 7.5Hz),7.42(t,4H,ArH,JHH=7.6Hz),4.91(pseudo t,4H,CpH),4.58(pseudo t,4H,CpH).13C NMR(101MHz,CDCl3,δ(ppm)):197.9(C=O),139.3(ArC),132.1(ArC),128.5(ArC),128.3 (ArC),79.6(CpC),74.8(CpC),73.3(CpC).HR-MS(ESI+): Calculated value: 395.0730, Actual value: 395.0734.

[0105] Example Solar Cell - General Method Solar cells were prepared according to the following method: Glass / ITO substrate (10~45Ω sq -1 ) were washed sequentially by ultrasonication with detergent, deionized water, acetone, and isopropyl alcohol for 5 to 30 minutes, respectively. The glass / ITO substrates were then dried in an oven at 80-120°C, then treated with oxygen plasma for 5-40 min, and finally transferred to a N2-filled glove box before use. PTAA solution in solvent: 0.6-4.1 mg mL -1 15-65 μL of the prepared PTAA solution was spin-coated onto the ITO substrate at 3500-7000 rpm for 18-50 s, and the substrate was sequentially annealed at 75-130 °C for 5-20 min. A 1.2–2.2 M perovskite precursor solution was prepared by mixing CsI, FAI, MABr, PbI2, and PbBr2 in 1 mL of a DMF:DMSO (3–15:1 / v:v) mixed solvent. x (FA y MA 1-y ) 1-x Pb(I z Br 1-z )3, where x = (0-0.95), y = (0-1), z = (0-1), and containing 3-15 mol % excess PbI2 relative to FAI. Then, 9.2–36.0 mol% MACl was added to the perovskite precursor solution and stirred for 0.5–12 h. 30–100 μL of the perovskite solution was spin-coated onto the glass / ITO / HTL at 350–1800 rpm for 5–20 s, followed by 3500–7000 rpm for 30–60 s. · 150-300 μL of solvent was slowly dripped onto the center of the film for 5-18 s before the end of spin-coating. The prepared perovskite films were then annealed on a hotplate at 90-150°C for 10-60 min.

[0106] To form the interface layer: Prepare FcTc2 powder, 0.3-2.2 mg mL -1 was dissolved in the solvent at a concentration of The prepared yellowish solution was stirred at room temperature (20-25°C) until the solution became clear. The solution was then transferred to a N2-filled glove box before use. · 60–180 μL of FcTc2 solution was spin-coated on top of the prepared perovskite at 4000–6000 rpm for 10–25 s, then transferred to a hotplate and annealed at 85–135 °C for 1–10 min. All spin-coating processes were carried out at room temperature (20–25 °C) in a N2-filled glovebox with O2 and H2O contents <10 ppm.

[0107] To complete the device: 10-30nm C60 in 0.3-1.5Å s -1 at a rate of 4×10 -6 Torr) 4-10 nm was thermally evaporated. BCP 0.2-1.2Å s -1 at a rate of 4×10 -6 The mixture was thermally evaporated to 350°C (torr). 70-120 nm silver electrodes at 0.5-3.0 Å s -1 at a rate of 4×10 -6 The mixture was thermally evaporated to 350°C (torr).

[0108] FIG. 3A shows a schematic diagram of a solar cell 300 according to this example.

[0109] Solar cell example 1 Cs 0.05 (FA 0.98 MA 0.02 ) 0.95 Pb(I 0.98 Br 0.02 A solar cell having a perovskite composition of 3 is prepared according to the general method as follows. Glass / ITO substrate (15Ω sq -1 ) were washed sequentially by ultrasonication with detergent, deionized water, acetone, and isopropyl alcohol for 20 minutes each. The glass / ITO substrate was then dried in an oven at 100°C, then treated with oxygen plasma for 10 min, and finally transferred into a N2-filled glove box before use. PTAA solution in chlorobenzene (CB) at 2.2 mg mL -1 35 μL of the prepared PTAA solution was spin-coated onto the ITO substrate at 6000 rpm for 30 s, and the substrate was sequentially annealed at 100 °C for 10 min. A 1.73 M perovskite precursor solution was prepared by mixing CsI, FAI, MABr, PbI2 (5 mol % excess relative to FAI), and PbBr2 in 1 mL of a DMF:DMSO (5:1 / v:v) mixed solvent. 0.05 (FA 0.98 MA 0.02 ) 0.95 Pb(I 0.95 Br 0.02 ) 3 to obtain a precursor having the chemical formula: Then, 15.5 mol % of MACl was added to the perovskite precursor solution and stirred for 2 h. · 60 μL of the perovskite solution was spin-coated onto the glass / ITO / HTL at 1000 rpm for 10 s, followed by 5000 rpm for 40 s. · 250 μL of CB was slowly dropped onto the center of the film for 12 s before the end of spin-coating. The prepared perovskite films were then annealed on a hotplate at 110 °C for 20 min.

[0110] To form the interface layer: For Fc-treated (FcTc2, Fc2Tc2, and Fc2Tc2) devices, prepare Fc compounds at 1 mg mL -1 The samples were dissolved in CB at a concentration of 0.01 mg / mL. If other concentrations are used, these are stated. The prepared yellowish solution was stirred at room temperature (20-25°C) until the solution became clear. The solution was then transferred to a N2-filled glove box before use. · 100 μL of FcTc2 solution was spin-coated on top of the prepared perovskite at 5000 rpm for 20 s, then transferred to a hotplate and annealed at 100 °C for 2 min. All spin-coating processes were carried out at room temperature (20–25 °C) in a N2-filled glove box with O2 and H2O contents <10 ppm.

[0111] To complete the device: 20nm C60 in 0.5Å s -1 at a rate of 4×10 -6 The mixture was thermally evaporated to 350°C (torr). 6nm BCP in 0.5Å s -1 at a rate of 1000 s in high vacuum (<4×10 -6 The mixture was thermally evaporated to 350°C (torr). 100 nm silver electrode at 1.0 Å s -1 at a rate of 4×10 -6 The mixture was thermally evaporated to 350°C (torr). The device area is reduced to 0.08 cm by a metal shadow mask. 2 It has been defined and characterized as:

[0112] The same procedure was used to form cells in which the interfacial layer was Fc2Tc2, or Fc3Tc2.

[0113] Comparison solar cell 1 A solar cell was formed as described in Solar Cell Example 1, but without the interfacial layer.

[0114] The performance of Example Solar Cell 1 and Comparative Solar Cell 1 were compared.

[0115] Experimental parameters and measurements The device performance was characterized according to the following methods: · XRD data were collected in reflection mode at room temperature on a Philips X'Pert diffractometer equipped with a CPS180 detector using monochromatic Cu-Kα (λ = 1.5418 A) radiation. · The surface and cross-sectional morphology of the perovskite films were obtained by SEM (QUATTROS, Thermal Fisher Scientific). XPS measurements were performed on an AXIS Supra XPS system. KPFM data were acquired via Bruker Dimension Kelvin Probe Force Microscopy in the Potential Channel equipped with a PFQNE-AL probe. · AFM-based characterization (AFM, KPFM and EFM) was performed through a Bruker Dimension ICON under ambient conditions, and a Ti / Ir coated silicon tip (ASYELELC-01-R2) with a resonant frequency of about 58-97 KHz was used in Scanning Kelvin Probe Microscopy (SKPM) and Electrostatic Force Microscopy (EFM) imaging. PTIR measurements were performed using a commercially available Bruker NanoIR2-FS setup consisting of an AFM microscope operated in contact mode (900–1800 cm -1 The test was carried out using the following test method: ·FTIR spectroscopy was performed by a Fourier transform infrared spectrometer (Tensor27, Bruker, Germany). Steady-state and time-resolved PL spectra were obtained on an Edinburgh FLS980 applied with excitation at a wavelength of 485 nm. The perovskite film thickness was obtained using a DektakXT stylus profiler. ·UV-Visible light absorption was measured by a UV-Visible light spectrometer (PerkinElmer model Lambda2S). · ToF-SIMS measurements were carried out using a TOF-SIMSV instrument (IONTOF GmbH, Cameca IMS 4F). The JV characteristics of the photovoltaic devices were carried out in a N2-filled glove box at room temperature by using a xenon lamp solar simulator (Enlitech, SS-F5, Taiwan). The light output was measured at 100 mW cm2 by a silicon reference cell (with a KG2 filter). -2 Prior to the J-V measurements, a 120 nm thick magnesium fluoride layer was deposited on the back of the ITO substrate to enhance the transmittance. All devices were calibrated to a maximum of 0.01 V s -1The measurements were performed using a Keithley 2400 sourcemeter under forward scan (from 1.20 V to -0.01 V) and forward scan (from -0.01 V to 1.20 V) sweep modes with a scan rate of 10 ms and a delay time of 10 ms. No conditioning was required before the measurements. The effective area was measured by a metal shadow mask, with a small area of ​​0.0414 cm. 2 , and centimeter area is 1.00 cm 2 The stabilized power output was determined by monitoring the stabilized current density output at the maximum power point (MPP) bias (extracted from the forward scan JV curve). ·EQE measurements were carried out by a QE-R EQE system (Enlitech, Taiwan). High-sensitivity EQE was measured by an integration system (PECT-600, Enlitech, Taiwan), where the photocurrent was amplified and conditioned by a lock-in instrument. Electroluminescence (EL) quantum efficiency (EQE EL ) was performed by applying an external voltage / current source through the instrument (ELCT-3010, Enlitech, Taiwan). · 1 H and 13 C{ 1 H} NMR spectra were recorded on a Bruker Avance 400 MHz spectrometer and referenced to residual solvent peaks of either CDCl3 at 7.26 and 77.2 ppm, or CD2Cl2 at 5.32 or 54.0 ppm, respectively. 1 The 1 H-NMR spectrum was fully assigned using 2D correlation spectroscopy. · Measure coupling constants in Hz. For peak force infrared (PFIR) imaging, an atomic force microscope (AFM) was used with a Bruker NanoIR2-FS setup operating in contact mode (900–1800 cm -1 The tip-sample distance during operation was determined by using a peak force tapping mode with a test range of 1480 cm. -1When fixed at 1000 K and the AFM tip scanned across the sample surface, high spatial resolution chemical mapping was produced while providing high quality IR spectroscopy and chemical imaging of the organic components in the perovskite film. A phase-locked loop synchronized the laser pulse with each peak force tapping cycle. A four-quadrant photodiode read and digitized the vertical deflection caused by the laser-induced contact resonance. The PFIR signal was obtained from the amplitude of the fast Fourier transform of the contact resonance. For the PFIR images, the scan area was 10 × 10 μm2 and the scan speed was 0.5 Hz. The resonance frequency of the AFM tip was 264 kHz. The laser power depended on this selected frequency.

[0116] As described herein, device stability was tested according to the following method: ·Long-term operational stability of the PVSC was performed by applying the PVSC under one sun-equivalent LED lamp under a N2-filled glove box (with O2 and H2O contents <10 ppm) at room temperature. The PVSC was biased at maximum power point (MPP) voltage and the PCE was measured with MPP-tracking routine by using a multipotentiostat (CHI1040C, CH Instruments, Inc.). A cooling system was applied to keep the device at 25°C. During the MPP test, the current density-voltage (JV) curves of the device were obtained every 12 hours to obtain a suitable load for the MPP. Thermal stability was performed by applying PVSC on a hotplate (HS 7, IKA) maintained at 85 °C in a N2-filled glove box (with O2 and H2O contents <10 ppm) and the patterns of PCE behavior of the devices were obtained through periodic JV measurements. · Water and oxygen stability tests were carried out by applying PVSC in ambient air (40-50% RH) without any light illumination, and the behavior pattern of the PCE of the devices was obtained through periodic JV measurements.

[0117] In density functional theory (DFT) calculations, ground state geometry optimization and vibrational frequencies for FcTc2, Fc2Tc2 and Fc3Tc2 molecules were performed by the B3LYP function combined with the 6-31g(d,p) basis set using the Gaussian16 package (version C01). The intramolecular electrostatic interactions were described by DFT-D3 (Grimme2006). Electrostatic potential (ESP) analysis was performed using the MULTIWFN software. The equivalent van der Waals surface (vdW) was calculated to be 0.001e / Bohr. 3 was set equal to

[0118] For stability testing according to the IEC 61215:2016 standard, the PVSC was encapsulated by a polyisobutylene (PIB) based polymer (PVS101®) and covered with 1.1 mm glass sheets on both sides of the device.

[0119] Damp heat testing was performed by keeping the encapsulated devices in an environmental testing chamber (EL-10KA, ESPEC, Japan) maintained at 85°C / 85% RH for 1000 hours.

[0120] For the temperature cycle test, the PVSCs were placed in an environmental test chamber (EL-04KA, ESPEC, Japan) and the temperature cycle was between −40 ± 2 °C and 85 ± 2 °C. The temperature change rate between −40 °C and 85 °C was set not to exceed 100 °C / h, and the temperature was kept stable for at least 15 min at the temperature points of −40 °C and 85 °C, respectively.

[0121] result FIG. 3B shows a scanning electron microscope image of the different layers of the Example Solar Cell 1.

[0122] FIG. 3C shows time-of-flight secondary ion mass spectrometry (ToF-SIMS) data, which reveals that the majority of FcTc2 (Fe +The results demonstrate that FcTc2 (see trace for ) is located at the surface of the perovskite film, between the ETL 106 and the perovskite layer 110. FcTc2 is deposited in the perovskite film at a stage when perovskite crystallization is complete. Furthermore, in theory, FcTc2 molecules are too large to be incorporated into the perovskite lattice. The presence of Fe signal in the perovskite bulk in the ToF-SIMS data is due to the fact that certain ion signals cannot suddenly disappear, but rather gradually decrease (the same signal tailing is seen for Ag, Pb, etc.).

[0123] X-ray diffraction (XRD), top-view SEM and UV-visible light absorption spectroscopy measurements were performed to study the crystallinity, morphology and light absorption of the perovskite films with and without FcTc2 treatment. All samples showed no obvious changes between the control devices and the devices containing the functional layer 108, indicating that the FcTc2 compound does not affect the crystallization and light-harvesting properties of the perovskite films.

[0124] To study how FcTc2 interacts with the perovskite, X-ray photoelectron spectroscopy (XPS) measurements were performed. The results are shown in FIG. 4. The binding energies corresponding to the Pb4f (FIG. 4A), I3d (FIG. 4B) and N1s (FIG. 4C) core levels of the FcTc2-treated perovskite device are all marginally shifted to higher values ​​compared to the control sample. This suggests improved binding of both anions and cations at the perovskite surface, which may be due to the strong binding between the surface ions and the FcTc2 interfacial layer 108. This binding is discussed further below with reference to FIGS. 23 and 24.

[0125] To study the effect of FcTc2 on the electrical properties of the perovskite films, Kelvin probe force microscopy (KPFM) measurements were carried out to examine the surface potential of the films, and the results are shown in Figure 5.

[0126] The perovskite film functionalized with FcTc2 (FIG. 5B) exhibits a reduced contact potential (near 50 mV) compared to that of the control sample (FIG. 5A), suggesting a direct interaction and surface charge transfer between the FcTc2 interfacial layer 108 and the perovskite layer 110. Furthermore, the FcTc2-functionalized perovskite displays a smaller potential distribution due to the surface potential difference (about 150 mV) than that of the control sample (about 250 mV). The uniform distribution of the surface contact potential is beneficial for effective charge carrier extraction and non-radiative recombination inhibition at the perovskite grain boundaries.

[0127] Time-resolved photoluminescence (TRPL) spectra were measured to evaluate the nonradiative recombination of the perovskite film. The fitting parameters are shown in Figure 6. The TRPL profile is calculated using the equation: τ 平均 =(A1τ1 2 +A2τ2 2 ) / (A1τ1+A2τ2), where the parameters A1 and A2 are the amplitudes of each decay component, and τ1, τ2 represent the time constants of the two types of decay: τ1 is the time constant for the fast decay component (related to the charge trapping process) and τ2 is the time constant for the slow decay component (related to the charge detrapping or carrier recombination process). The time series was fitted using a biexponential decay with fast and slow components based on

[0128] The carrier lifetime was significantly increased from 1166.74 ns to 2159.22 ns by the incorporation of FcTc2 (see also Table 1 below). The carrier lifetime is defined as the average time it takes for a minority of carriers to recombine. The increased carrier lifetime seen in Table 1 is comparable to that of the device without an interface layer, 0.5 mg mL -1 A device containing an interface layer with an FcTc2 concentration of 1.0 mg mL -1 and a device containing an interface layer with an FcTc2 concentration of 2.0 mg mL -1This is consistent with the enhanced steady-state PL intensity shown in Figure 7, which shows the photoluminescence intensity for a device including an interfacial layer with a FcTc2 concentration of 108. These results indicate reduced non-radiative recombination levels for devices including the interfacial layer 108, likely due to reduced perovskite surface defects. [Table 1]

[0129] Table 2 shows the photovoltaic parameters of the best performing PSCs modified with different concentrations of Fc2Tc2. [Table 2]

[0130] In triple cation mixed halide perovskites, the chemically reactive components at the surface of the perovskite layer 110, e.g., MA + and I - can volatilize and migrate via photo / thermal effects, resulting in the degradation of the photovoltaic performance. To estimate the effect of FcTc2 on perovskite stability, MA of control and FcTc2-functionalized perovskite films was + The cations were probed by peak force infrared (PFIR) microscopy under illumination and thermal conditions. PFIR mapping was performed on the MA in the solar cell example 1. + The intensity and distribution of cations are well maintained after 1000 hours of aging (see Figures 8A and 8B), while comparative solar cell 1 shows a significant reduction in the intensity of the MA signal and a significant broadening of the distribution (Figures 8C and 8D). These results suggest that ion migration and volatilization are more likely in the absence of an interfacial layer, resulting in an increase in surface defects, which in turn affects the operational stability of perovskite devices. However, FcTc2 can firmly anchor surface ions and reduce migration, resulting in a more uniform and stable surface component distribution.

[0131] FIG. 9 shows the device current density-voltage (JV) curves for Example Solar Cell 1 and Comparative Solar Cell 1 under sunlight irradiance by AM1.5G simulation, with the concentration of FcTc2 optimized to 1.0 mg mL -1 As a result, the best performance was obtained (see the comparative experimental results below in Table 3). [Table 3]

[0132] As shown in FIG. 9, the comparative solar cell 1 has an open circuit voltage (V OC ), 25.25mA cm -2 Short circuit current density (J SC ) and a maximum PCE of 23.02% with a fill factor (FF) of 80.45%. Solar Cell Example 1 showed an increased V OC , 25.68mA / cm 2 J SC and FF of 82.32%, an improved PCE of 25.03%. Solar Cell Example 1 also exhibited low hysteresis. The corresponding external quantum efficiency (EQE) spectrum (shown in FIG. 10) shows a small variation in the integrated JV measurement from the values ​​obtained. SC The Example Solar Cell 1 was also measured at the maximum power point (MPP) to obtain a stabilized photocurrent of 23.70 mA cm-2 and a stabilized PCE of 24.17%.

[0133] One of the best performing devices, with the structure of solar cell example 1, was certified by an independent solar cell-accredited laboratory for certification (Institute of Metrology, China), where it had a PCE (V OC =1.179V, J SC =25.59mA cm -2, and FF=80.60%, which is the highest certified efficiency to date among all inverted PVSCs. PCE measurements are also provided in FIG. 11 (under AM1.5G simulated sunlight irradiance), which shows a histogram of PCE values ​​for 30 devices with and without the interfacial layer. The PCE measurements showed good reproducibility, with an average PCE of 22.52% for Comparative Solar Cell 1 and 24.47% for Example Solar Cell 1, respectively.

[0134] In addition, the photovoltage loss (V OC A quantitative analysis of the EQE (loss) was performed for Comparative Solar Cell 1 and Example Solar Cell 1 according to detailed balance theory. The EQE was 1.5% for the control device and 7.0% for Example Solar Cell 1. EL were obtained from electroluminescence (EL) spectra, and ΔV3 (V from nonradiative recombination) of 108.57 and 68.75 mV, respectively. OC It has been suggested that FcTc2 acts as an interface modifier that significantly suppresses nonradiative recombination. OC The loss component values ​​(ΔV1, ΔV2, ΔV3) were calculated according to Table 1. The calculated values ​​are summarized in Table 4. OC The losses are among the lowest of any inverse PVSC. [Table 4]

[0135] Figure 25 shows the electrostatic potential distribution of different Fc compounds via density functional theory (DFT) simulations. The oxygen atoms in the carboxylate end groups in each functionalized Fc compound show the strongest negative electrostatic potential and may preferentially interact with cations in the perovskite structure. Furthermore, the electrostatic potentials in the carboxylate units for FcTc2, Fc2Tc2, and Fc3Tc2 are −29.79, −29.17, and −30.50 kcal mol−1, respectively. -1The electrostatic potential difference is related to the conformation of the molecule, and the relatively small electrostatic potential value for Fc2Tc2 at the carboxylate unit may be attributed to the most balanced molecular conformation. The various Fc unit numbers slightly affect the electrostatic strength of different systems, but do not change the overall electrostatic distribution and the interactions between perovskite and Fc-based compounds.

[0136] The interaction between the functionalized Fc compounds and the perovskite surface was investigated using X-ray photoelectron spectroscopy (XPS) (Figures 25c and d, 31, 32). The binding energies for the Pb4f and I3d core levels of the Fc-treated perovskite films were all marginally shifted to higher levels than those of the control films, suggesting modified electronegativity at the perovskite surface and demonstrating the interaction between the functionalized Fc compounds and uncoordinated sites at the perovskite surface. In addition, the UV-visible absorption spectra and atomic force microscopy (AFM) images in Figures 33, 34 show that the interaction does not affect the optical properties and morphology of the perovskite films.

[0137] To understand the influence of the organometallic motif, the pattern of Fc valence movement through XPS was estimated as shown in Figure 25e. The Fe2p orbital spectrum shows that the iron center is located at Fe 3+ and Fe 2+ They exist in both states, 2p 3 / 2 Then, 710.1 eV (2p 1 / 2 723 eV), 2p 3 / 2 Then, 708 eV (2p 1 / 2 Furthermore, as the number of Fc units increases, the binding energy of Fe 3+ / Fe 2+The ratio of Fc to iodide drops, implying redox limitation of Fc compounds bound to the surface of the perovskite film. This change is consistent with the valence change previously reported for ferrocene or cobaltocene and may be due to iodide anions released by chemical damage to the perovskite crystal surface acting as counterions for the oxidized Fc cations.

[0138] To gain deeper insight into the charge transfer between functionalized Fc compounds and perovskite, electrostatic force microscopy (EFM) was performed on the perovskite films (Figures 25f, 25g, 35), providing direct information on carrier type and concentration.

[0139] EFM gives a powerful tool to discover direct charge transfer in mixed electronic systems. In the EFM test protocol, a bias voltage (-3 to 3 V in steps of 1.5 V) is applied to the tip of the probe to allow extraction of Coulombic forces. Figures 1f and 1g show the phase shift mapping over the scan area at different bias voltages integrated in one image for comparison. The statistics of the phase angle under different bias voltages are shown in Figures 34 and 35 by counting the data in Figures 1f and 1g. Further statistical measures are shown in Figure 1h by applying a parabolic fitting to it. The negative shift of the symmetry axis of the fitted parabola represents the negative charge induced at a point or region of the surface.

[0140] Pristine and Fc2Tc2-treated films are representative and shown in Figures 25f and 25g, which show the integrated phase shift mapping over the entire scan area at various bias voltages (from -3V to 3V), with the corresponding phase angle statistics shown in Figures 36 and 37. Both the pristine and Fc-treated perovskite films show a readily discernible degree of phase shift. In Figure 25h, the negative shift in the symmetry axis of the fitted parabola corresponds to the negative charge arising at the sample surface. 31In the Fc-modified perovskite, some Fc species are already ionized due to their high electron delocalization, leading to an increase in the number of negative charges, indicating that electrons are transferred from the Fc compounds to the perovskite surface, leading to charge redistribution at the perovskite surface.

[0141] Surface engineering of perovskite films can tune the work function and carrier concentration. Kelvin probe force microscopy (KPFM) was applied to determine the surface potential of perovskite films. Contact potential difference (CPD) images of pristine and Fc-treated perovskite films are shown in Figures 26a-26d. The Fc-modified perovskite films show gradually increasing CPD values ​​compared to the pristine films following the increase in Fc units originating from the interfacial charge transfer. Furthermore, the Fc-modified perovskite films show a steadily growing uniformity of the surface potential with the introduction of further Fc units (Figure 26e). The reduced surface potential difference can accelerate and homogenize the charge extraction efficiency as well as reduce the non-radiative recombination loss at the interface.

[0142] The surface work function of perovskite film modifications with different Fc compounds was also determined by calibrating the work function with Au reference. In Figures 26e-26h, the pristine perovskite film yields a work function of 4.74±0.07 eV. Surface manipulation via Fc compounds causes a negative shift in the work function, and an increase in the number of Fc units results in a further negative shift, leading to a value of 4.46±0.02 eV at a charge of around 300 meV for the Fc3Tc2 modified perovskite film. Furthermore, the altered work function only occurs within the surface layer of the perovskite film, since the Fc compounds are only bound to the perovskite surface according to the TOF-SIMS results in Figure 38.

[0143] To examine how surface manipulation affects the interfacial charge extraction and recombination, steady-state and time-resolved photoluminescence (PL and TRPL) were measured on the perovskite / ETL films (glass / perovskite / C 60The functionalized Fc-treated perovskite membranes (having the structure of Fc2Tc2) were first carried out in Fig. 26i and Fig. 39, where the functionalized Fc-treated perovskite membranes show a significant decrease in PL intensity compared to that of the control. Furthermore, the carrier lifetime via fitting of the TRPL spectrum decreases from 189.7 ns to 33.5 ns upon increasing the number of Fc units. The reduction in PL intensity and lifetime indicates the facilitated charge extraction from the perovskite to the ETL. PL mapping in the perovskite / ETL membranes was carried out (Fig. 40). The PL mapping intensity was counted and the integral values ​​are presented in Fig. 26j, where the x-axis is the PL mapping intensity and the integral area represents the PL homogeneity. The control membrane shows heterogeneous PL intensity, suggesting an unbalanced charge extraction efficiency. In contrast, the incorporation of Fc compounds and the optimization of Fc units to Fc2Tc2 leads to a more uniform PL emission and a reduced PL intensity compared to that of the control membrane, further proving that the carrier extraction is accelerated and homogenized due to the introduction of Fc compounds.

[0144] In addition to charge extraction, carrier recombination and interface defect states were also investigated. Space-charge-limited current (SCLC) techniques were first implemented in electron-only devices (Figures 41 and 42) to measure the trap-filling voltage V TFL =eN t L 2 / 2εε0 gives the trap density (N t ) was sought.

[0145] Electron-only devices with the FTO / TiO2 / perovskite / Fc / C60 / BCP / Ag structure were fabricated and the defect density (N) was calculated. In the SCLC regime, the current is dominated by charge carriers injected from the contacts, and the current-voltage characteristics become quadratic (I~V 2 ). Figure 38 shows the J-V curves of the fabricated device on a log-log scale, including the ohmic region, the trap-filling-limited (TFL) region, and the Child region. In the TFL region, the trap-state density (N t ) can be calculated by the following formula:

[0146] Nt=2εε0VTFL / qL 2 (S1)

[0147] where ε and ε0 are the relative dielectric constant and the vacuum permittivity, respectively. TFL is the set voltage of the TFL region, q is the elementary charge, and L is the thickness of the perovskite thin film.

[0148] In FIG. 26k, after functionalization with Fc compounds, the trap filling voltage gradually decreases from 0.745 V (control device) to 0.194 V (Fc2Tc2 modified device), but increases to 0.489 V for the Fc3Tc2 analog. A similar trend can be observed in the variation of the ideality factor (n) in FIG. 34 , which decreases from 1.71 to 1.25 after the introduction of Fc2Tc2, but increases to 1.58 when using Fc3Tc2 for surface modification. These findings demonstrate that the incorporation of functionalized Fc molecules can efficiently suppress interfacial defects and carrier recombination; however, this effect is mitigated when excess Fc units are included.

[0149] Electroluminescence (EL) measurements in the dark were carried out under forward voltage bias (Figures 44 and 45). The films treated with Fc2Tc2 show a more dominant emission intensity and a narrower emission range compared to the control, further confirming the reduced non-radiative recombination losses. 35 Furthermore, in Figure 26k, the Fc2Tc2 modified device had an EQE of 8.1%. EL They demonstrate an efficiency of 3.1%, which they recommend as the highest of any inverse perovskite photovoltaic device to date. In comparison, the control device has an EQE of 3.1% under the same conditions. EL It only shows efficiency.

[0150] To investigate the effect of surface modification on PV performance, inverted PV devices were fabricated with the configuration of indium tin oxide (ITO) / poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) / perovskite / Fc molecule / C60 / 2,9-dimethyl-4,7-diphenyl-1,10 phenanthroline (BCP) / silver (Ag) (Figures 27a and 27b). Figures 27c and 27d show the current-voltage (JV) curves and efficiencies of PSCs containing different Fc compounds. The control device showed a maximum PCE of 23.06%, with an open circuit voltage (V OC ) is 1.112V, and the short circuit current density (J SC ) is 25.21mA cm -2 After the introduction of Fc compounds, the PSC showed a significantly increased V OC and FF are shown (Table 5). [Table 5]

[0151] The Fc2Tc2 treated device produced a heading efficiency of 25.43%, V OC is 1.191V, J SC is 25.47mA cm -2 , FF is 83.82%, with non-negligible hysteresis compared to the control device (Figure 27e and Figure 46). The PV performance with varying concentrations of Fc compound is summarized in Figures 47 and 48.

[0152] The external quantum efficiency (EQE) spectrum (Fig. 27f) shows that the integral J deviates only slightly from the JV measurement. SC The stabilized efficiency of the Fc2Tc2 modified device was also evaluated at the maximum power point (MPP) and was found to be 24.25 mA cm 2and a stabilized PCE of 25.22% (Fig. 27g). Moreover, the devices also showed very good reproducibility and negligible deviations for each PV parameter, with an average PCE of about 22.6% for the control device and 25.0% for the Fc2Tc2-modified device (Fig. 27h). In addition, the energy loss analysis showed nonradiative recombination losses of 85.94 mV and 64.97 mV in the control and Fc2Tc2-modified devices, respectively (Figs. 49 and 50, Table 6), further confirming the significant contribution of Fc2Tc2 to the improved performance of PSCs. [Table 6]

[0153] The long-term operational stability of the encapsulated devices in MPP under continuous single solar irradiation in N2 atmosphere was examined. The Fc2Tc2 modified devices demonstrated extremely good stability with a PCE of over 93% after 4000 hours (>T93) compared to the control devices (Figure 51), losing over 60% of the initial PCE after 2500 hours. The results showed comparable operational stability to the FcTc2 based devices (Figure 51).

[0154] After determining the extremely excellent small area PV performance achieved by Fc2Tc2 modification, the inventors further developed a large area cell (1.008 cm 2 were fabricated and their performances estimated. Figure 28a shows the J-V curves of the best performing large area PSCs with and without Fc2Tc2. The control device yielded a PCE of 21.58% and a J SC is 25.13mA cm -2 , V OC = 1.108 V, and FF of 77.50%. In contrast, the Fc2Tc2 modified device has a FF (79.76%) and V OC (1.184 V), ultimately achieving the hit efficiency of 23.77%. Furthermore, in Figure 28b, the Fc2Tc2 modified device showed a 23.05 mA cm under a bias voltage of 1.02 V. -2The stable photocurrent output of 20 and the stabilized PCE of 23.51% were observed. Figure 28c shows the V OC The statistical distribution of V and FF for modified devices is shown. OC and FF are higher than those of the control device, consistent with the small-area device results in Figure 28h, suggesting that the improved performance of the large-area device also originates from the accelerated interfacial charge transfer and suppressed nonradiative recombination.

[0155] To further evaluate the PV performance uniformity of the large area device, we recorded the JV curves of our device positioned at five separate points of the active area of ​​the device, namely, at the center and four corners (Figure 28d). 2 All PV metrics of the Fc2Tc2-based devices collected from the JV curves in these five areas using a mask with a square aperture area of ​​10 μm showed very little variation (Table 7). [Table 7]

[0156] More notably, in FIG. 28e, the Fc2Tc2 modified device exhibited larger FF and V than the control device, according to the statistics of small area PV metrics captured in the large area device. OC These results show that PV performance reaches optimal values ​​across the square centimeter scale after Fc2Tc2 modification.

[0157] To identify the reason for the improved PV performance and homogeneity, steady-state PL measurements were performed in five separate regions of the perovskite / ETL film (Figure 28f). The Fc2Tc2-treated samples show more consistent PL intensity compared to the control ones, as shown in Figure 52. The number of collected samples was expanded and normalized based on the highest PL intensity in each film. As shown in Figure 28f, the CV value of the modified film is 0.040, which is lower than that of the control (0.893), indicating more uniform carrier extraction and transfer in the square centimeter scale. In addition, KPFM characterization was applied to evaluate the surface potential variation of different regions in the perovskite film. In Figures 53 and 54, the modification via Fc2Tc2 leads to more uniform surface potential in independent regions, respectively. Although the potentials at different locations deviate slightly for both the control and target membranes, the Fc compound can reduce the potential difference for each localized location, enabling optimal carrier extraction efficiency across a wide range of large-area perovskite devices, thus enabling scalable PSCs to achieve performance optimization at different locations.

[0158] stability To investigate the effect of FcTc2 functionalization on device stability, the patterns of efficiency behavior under various conditions were monitored.

[0159] First, the operational stability of the unencapsulated devices was examined via maximum power point (MPP) tracking under continuous single solar illumination in a N2 atmosphere. As shown in Figure 12, Example Solar Cell 1 retained its initial efficiency for the first 200 hours and showed only less than 2% decay over 1500 hours. In comparison, Comparative Solar Cell 1 decreased to 72% of its initial efficiency.

[0160] The stability of the unencapsulated devices was further measured under thermal (FIG. 13A) and ambient (FIG. 13B) conditions, respectively. In both cases, it can be seen that the performance of Comparative Solar Cell 1 dropped significantly below 80% of the initial efficiency beyond 800 hours. In contrast, the Solar Cell Example 1 device exhibited a T98 (time to 98% of initial efficiency) of 2000 hours under ambient conditions and 1500 hours under continuous heating, respectively. Without wishing to be bound by any theory, it is believed that chemically reactive moieties (e.g., MA) on the perovskite surface may be the cause of the degradation of the perovskite. + and I - Since FcTc2 can easily volatilize and migrate via light-, moisture-, and thermal-degradation, FcTc2 can improve stability through the formation of additional bonds with the perovskite surface ions and blocking the migration of any mobile ions.

[0161] In addition, stringent stability measurements were performed according to the IEC 61215:2016 standard, which is the most used international standard for mature photovoltaic technology. As shown in FIG. 14A, the solar cell example 1 device successfully passed the main points of the IEC 61215:2016 standard under humid and heat conditions by exhibiting a T95 of over 1000 hours under humid heat test (85° C. / 85% RH). Furthermore, as shown in FIG. 14B, under cold (−40° C.) and heat (85° C.) cycle shock, the solar cell example 1 device retained over 85% efficiency after 200 cycles; this was significantly more efficient than the comparative solar cell 1 (which retained 40% efficiency after 200 cycles). Taken together, these data indicate that the FcTc2-functionalized PVSC device exhibits very promising efficiency and stability. Perovskite solar cells with such functional interface layers have a promising future for commercialization and competitive with silicon solar cells.

[0162] Solar Cell Example 2 MAPbI3-based devices were fabricated as follows: The ITO / glass substrate cleaning and hole transport layer (PTAA) deposition procedures were the same as those discussed above for Solar Cell Example 1. 0.05 (FA0.98 MA 0.02 ) 0.95 Pb(I 0.95 Br 0.02 ) Consistent with 3 series device manufacturing. Prior to use, a MAPbI3 precursor solution was prepared by mixing 1.55 M MAI and 1.63 M PbI2 in 1 mL of DMF:DMSO (5:1 / v:v) mixed solvent and stirring for 2 h. · 60 μL of the perovskite solution was spin-coated onto the glass / ITO / HTL at 2000 rpm for 10 s, followed by 6000 rpm for 30 s. 250 μL of CB was slowly dropped onto the center of the film 7 s before the end of spin-coating. The prepared perovskite film was then annealed on a hotplate at 100 °C for 30 min. The procedures for deposition of the FcTc2 interfacial layer and evaporation of the metal electrodes are as described in Solar Cell Example 1.

[0163] Solar Cell Example 3 FAPbI3-based devices were fabricated as follows: ITO / glass substrate cleaning and hole transport layer (PTAA) deposition procedures are as for Solar Cell Example 1. The FAPbI3 precursor solution was prepared by mixing 2 M FAI and 2.06 M PbI2 in 1 mL of DMF:DMSO (8:1 / v:v) mixed solvent. Then, 35 mol% MACl was added to the perovskite precursor solution and stirred for 2 h. · 60 μL of the perovskite solution was spin-coated onto the glass / ITO / HTL at 6000 rpm for 40 s. 250 μL of CB was slowly dropped onto the center of the film 25 s before the end of spin-coating. The prepared perovskite film was then annealed on a hotplate at 135 °C for 1 h. The procedures for deposition of the FcTc2 interfacial layer and evaporation of the metal electrodes are as described in Solar Cell Example 1.

[0164] Solar Cell Example 4 Cs0.05 (FA 0.85 MA 0.15 ) 0.95 Pb(I 0.85 Br 0.15 ) Three series devices were fabricated as follows: The ITO / glass substrate cleaning and hole transport layer (PTAA) deposition procedures were as described in Device Example 1. CsI ​​was prepared by mixing CsI, FAI, MABr, PbI2 (10% molar excess relative to FAI) and PbBr2 in 1 mL of a DMF:DMSO (5:1 / v:v) mixed solvent. 0.05 (FA 0.85 MA 0.15 ) 0.95 Pb(I 0.85 Br 0.15 A 1.5 M solution of a perovskite precursor having the chemical formula: 60 μL of perovskite solution was spin-coated on the glass / ITO / HTL at 5000 rpm for 30 s. 250 μL of CB was slowly dropped onto the center of the film 7 s before the end of spin-coating. The prepared perovskite film was then annealed on a hotplate at 100 °C for 30 min. The procedures for deposition of the ·FcTc2 interfacial layer and evaporation of the metal electrodes are as described in Device Example 1.

[0165] Comparison solar cells 2~4 Comparative Solar Cells 2-4 were prepared as described for Solar Cell Examples 2-4, respectively, except that the FcTc2 layer was omitted.

[0166] Table 8 shows the increased PCE for each of the comparative devices 2-4 upon inclusion of the FcTc2 interfacial layer. [Table 8]

[0167] The benefits of the interface can be further understood with reference to Figures 15, 16 and 17, which compare the performance of different perovskite compositions with and without an FcTc2 interfacial layer.

[0168] FIG. 15A shows the JV curve of the best performing PVSC of Solar Cell Example 2, and FIG. 15B shows a histogram of the measured PCE values ​​for 20 Solar Cell Example 2 devices.

[0169] FIG. 16A shows the JV curve of the best performing solar cell Example 4 device, and FIG. 16B shows a histogram of the measured PCE values ​​for 20 solar cell Example 2 devices.

[0170] FIG. 17A shows the JV curve of the best performing solar cell Example 3 device, and FIG. 17B shows a histogram of the measured PCE values ​​for 20 solar cell Example 3 devices.

[0171] Solar Cell Example 5 An "electron-only" solar cell device was fabricated with the following structure: glass substrate (102) / FTO+TiO2 (contact 114) / perovskite layer (110) / interfacial layer FcTc2 (108) / C60 (ETL 106) / BCP / Ag contact 104 (as in the inverted structure shown in Figure 1B and Figure 3, omitting the hole transport layer 112 and replacing ITO with FTO+TiO2).

[0172] Comparison solar cell 5 Comparative Solar Cell 5 was prepared as described for Solar Cell Example 5, except that the FcTc2 interfacial layer was omitted.

[0173] 18A and 18B show space charge limited current (SCLC) measurements of Example Solar Cell 5 and Comparative Solar Cell 5, respectively. The current density is significantly higher at the trap filling limit voltage (V TFL ) is achieved, the increase is greater.

[0174] Applying the trap filling limit voltage, Nt=2εε0V TFL / eL 2The trap density can be calculated by the formula: where e is the elementary charge, ε is the relative dielectric constant of the perovskite, ε0 is the vacuum dielectric constant, L is the thickness of the perovskite layer, and N t is the trap density of the perovskite film.

[0175] The calculated trap densities were 2.76 × 10 for Comparative Solar Cell 5 and Example Solar Cell 5, respectively. 15 and 8.27×10 14 , indicating that the presence of the FcTc2-modified perovskite film reduces the level of trap density.

[0176] As shown in Figures 18A and 18B, the carrier mobility in the "electron-only" device is 2.72 x 10 for Comparative Solar Cell 5, based on SCLC measurements. -4 cm 2 V -1 s -1 5.52 x 10 for FcTc2 modified solar cell example 5 -4 cm 2 V -1 s -1 Assuming that all layers other than the interface layer in Comparative Solar Cell 5 and Example Solar Cell 5 are identical, this improved carrier mobility can be attributed to faster electron transfer induced by the FcTc2 modified interface.

[0177] As shown in FIG. 18C, the carrier lifetime at the perovskite / ETL interface of Example Solar Cell 5 is shorter than that at the pristine perovskite / ETL interface of Comparative Solar Cell 5, further indicating that electron extraction is accelerated via FcTc2.

[0178] Since a similar improvement in interfacial carrier transport and extraction has not been demonstrated by the use of organic interfacial materials (e.g., DPC in FIG. 20 or BA in FIG. 21), we can speculate that improved interfacial carrier dynamics is imparted here by the Fc moieties. Thus, without wishing to be bound by theory, it can be concluded that the use of a metallocene interfacial layer facilitates electron transfer at the perovskite / ETL interface.

[0179] Comparison solar cell 6 A solar cell was prepared as described for Solar Cell Example 1, except that the ferrocene-based material ferrocenyl bis-phenyl (FcPh2) was used as the interface material. The molecular structure of FcPh2 is shown in the inset in Figure 19B.

[0180] It can be seen from FIG. 19B that the short circuit current Jsc and fill factor FF are increased for the FcPh2 interfacial layer 108 compared to the control device of FIG. 19A, which does not have an intermediate layer. However, the FcPh2 modified PVSC did not show a significant improvement in PCE compared to the control. Without wishing to be bound by any theory, this may be due to the fact that neither the phenyl nor the ferrocene units can bond or interact with the perovskite and therefore cannot replace the effect of the carboxylate of FcTc2 on defect passivation and carrier transport.

[0181] Comparison solar cell 7 A solar cell was prepared as described for Solar Cell Example 1, except that diphenyl carboxylate (DPC) was used as the interface material. The molecular structure of DPC is shown in the inset in Figure 20B.

[0182] Referring to FIG. 20B, the short circuit current J of the DPC-modified PVSC SCIt can be seen that both the FF and FF are reduced compared to the control device in Figure 20A which does not contain an interfacial layer. Without wishing to be bound by any theory, this may be due to an electron transport barrier at the perovskite / ETL interface caused by poor conductivity of the organic DPC interfacial layer.

[0183] Comparison solar cell 8 A solar cell was prepared as described for Solar Cell Example 1, except that butyl acetate (BA), a representative ester with a high boiling point, was used as the interface material. The molecular structure of BA is shown in the inset in FIG. 21B.

[0184] Referring to FIG. 21B, the short circuit current J of the BA-modified PVSC SC It can be seen that both the FF and FF are reduced compared to the control device in Figure 21 A which does not contain an interfacial layer. Without wishing to be bound by any theory, this may be due to an electron transport barrier at the perovskite / ETL interface caused by poor conductivity of the organic BA interfacial layer.

[0185] Density functional theory (DFT) simulation and electrostatic potential (ESP) analysis Density functional theory (DFT) simulations were performed to study the interactions between the perovskite surface and the FcTc2 molecules. The (001)PbI2-terminated perovskite surface was chosen as a model because it has been proven to be stable by its lowest energy configuration. After the ordered interface, enhanced binding of O from the FcTc2 and Pb from the Pb-perovskite surface was observed within a few picoseconds (Figures 23A and 23B, with bond lengths L Pb-O (See the decrease in .) Due to the interfacial rearrangement, the molecular dynamics reach a stable equilibrium state where the Pb-O bond length is simulated to be 2.65 Å (See FIG. 23C).

[0186] The electrostatic potential (ESP) analysis of FcTc2 shown in Figure 24 indicates the high electronegativity of O in FcTc2 (-29.79 kcal mol-1 ) (The electronegativities of the O, S and H atoms are -29.79 kcal mol -1 , -8.12 kcal mol -1 and 15.16 kcal mol -1 This further supports the formation of strong Pb-O bonds between the perovskite surface and FcTc2.

[0187] The XPS analysis discussed with respect to FIG. 4, combined with the DFT simulations in FIG. 23 and the ESP analysis in FIG. 24, indicate that there is a strong interaction between the perovskite and FcTc2 that is beneficial for both passivating surface defects and stabilizing surface components in the perovskite.

[0188] Thus, from these DFT simulations in Figure 23, it can be seen that FcTc2 molecules can attach to uncoordinated Pb defects at the perovskite surface via Pb-O bonding or bond formation. This interaction (as well as the strong Pb-O bonding or bond) between FcTc2 and perovskite can reduce the trap state density and suppress non-radiative recombination, an effect demonstrated by the extended carrier lifetime derived from the TRPL spectra (Table 1 and Figure 6) and the reduced defect density calculated from the SCLC curves (see Figure 18).

[0189] Overall, the realization of highly efficient perovskite solar cells can be attributed, at least in part, to the following effects discussed herein: (i) interface defect passivation: the interface layer 108 (e.g., FcTc2) can attach to uncoordinated Pb defects at the perovskite surface, e.g., via Pb-O bonding, to reduce the trap state density and suppress non-radiative recombination (see Figs. 23, 24); (ii) Acceleration of electron transport and extraction. The fast electron transfer properties of metallocenes (e.g., ferrocene in FcTc2) can accelerate electron transport and extraction at the perovskite / ETL interface, which is not possible with insulating organic interface materials (see Figures 20 and 21); and (iii) Improved structural compatibility and molecular flexibility. By applying FcTc2 and especially its thiophene-carboxylate side chains to modify the perovskite interface (potentially providing O and S atoms), better structural compatibility is achieved. Compared with traditional rigid inorganic materials, FcTc2 has better molecular flexibility and can interact more strongly with the perovskite and transport layer interfaces.

[0190] Description of funds This invention was supported by ECS Grant (21301319) and the Natural Science Foundation of Guangdong Province (2019A1515010761), as well as Imperial College London via the Sir Edward Frankland BP Chair Endowment.

[0191] Appendix 1: Photovoltage Loss (V OC,損失 )calculation Detailed V OC,損失 can be described by the formula listed below:

number

[0192] As a result, the energy loss can be divided into three parts, ΔV1, ΔV2 and ΔV3, which are respectively: E g represents the voltage loss induced by radiative recombination, energy losses from blackbody radiation, and non-radiative recombination;

[0193] Photovoltaic band gap (E g、PV ) is the maximum point of the Gaussian-like derivative ∂EQE / ∂λ (λ g ) was obtained from the inflection points of the EQE spectrum by setting E g、PV is defined as the average peak energy at the absorption edge of the distribution and should be taken as the convention for the determination of the bandgap energy of any solar cell. Since this represents the external properties of the photovoltaic device and not the internal properties of the photovoltaic material, the use of the average peak energy may allow a more accurate estimation of the bandgap of the solar cell device.

[0194] According to previous reports, the V OC is the formula

number

number

[0195] According to the Shocklake-Weisser limit (SQ limit): (1) EQE PV is described by the Heaviside step function, where EQE PV (E)=

number

[0196] Therefore, J in the SQ limit SC and J0:

number

number

[0197] Considering the theory of SQ limits, V OC SQ is divided by three loss components into V OC It can be decomposed into: 1st V OC Loss component is less than 100%, non-ideal EQE PV In this situation, the short circuit current is expressed as:

number

[0198] V OC SQ was calculated as follows:

number

[0199] 2nd V OC The loss component comes from the energy losses associated with the excess thermal radiation of the solar cell in the dark. PV falls within the sub-bandgap region, where blackbody radiation increases with decreasing light energy. Therefore, this sub-bandgap EQE PV increased the dark saturation current. SC rad J SC and the dark saturation current in this condition is equal to:

number

number

[0200] 3rd V OC Loss component ΔV OC nonrad is due to non-radiative recombination in the device:

number

[0201] According to Equation 4 and Equation 11,

number

number

[0202] Solar Cell Example 1 and Comparative Solar Cell 1 exhibit a similar ΔV1 of about 274 mV.

[0203] As shown in Figure 44, the PSCs with and without Fc2Tc2 exhibit a similar ΔV1 of about 274 mV, indicating that the radiative recombination does not change after surface treatment. The EQE of the device is E g Because it projects into the lower area resulting in more blackbody radiation, the high sensitivity EQE below the bandgap can be characterized and ΔV2 calculated, which is 20.67 mV and 31.50 mV for Example Solar Cell 1 and Comparative Solar Cell 1, respectively.

[0204] ΔV3 is the V from nonradiative recombination OC loss and can be estimated by equation S22, where EQE EL is the EQE of electroluminescence (EL). ΔV3 of Comparative Solar Cell 1 and Solar Cell Example 1 can be calculated to be 108.57 and 68.75 mV, respectively. This result further confirms that the functional Fc molecule plays a role in accelerating interfacial charge transfer and reducing non-radiative recombination.

[0205] The external ideality factor (n) is qV OC =E g −nkT|ln(I0 / I), where I0 is the normalization factor, T is the absolute temperature, I is the incident light intensity, q is the elementary charge, and E g is the band gap, k is the Boltzmann constant, and T is the absolute temperature. In general, in Figure 39, an ideality factor of 1 is associated with bimolecular bond-to-bond radiative recombination of carriers, or dominating Shockley-Read-Hall (SRH) trap-assisted recombination at a fixed charge carrier density, while an ideality factor of 2 is associated with dominant SRH recombination at no fixed charge carrier density.

Claims

1. first electrode; second electrode; The perovskite layer and electron transport layer installed between the first and second electrodes; and A photovoltaic cell comprising an interface layer positioned between the perovskite layer and the electron transport layer and in direct contact with the perovskite layer, wherein the interface layer comprises at least one substituent R containing at least one of O, S, N, or P atoms １ A photovoltaic cell comprising an interface compound containing metallocene substituted by a metallocene.

2. The aforementioned interface compound is a compound of formula (I): [metallocene] p (I) During the ceremony: Metallocenes have two aromatic or heterocyclic aromatic groups Ar １ It is a metallocene group containing a metal bonded to it; p is at least 1; At least one metallocene has at least one substituent R １ It is replaced by; The photovoltaic battery according to claim 1.

3. The compound of formula (I) is formula (Ia): 【Chemistry 1】 During the ceremony: M is a metal ion; Ar １ However, in each event, it is a monocyclic, polycyclic, or heterocyclic aromatic group; M and the two Ar １ The group forms the metallocene; at least one Ar １ However, at least one R １ It is replaced by; R ２ However, it is a group that satisfies the valence of M; q is 0 or a positive integer; R ３ is, in each event, independently H or a substituent; A photovoltaic battery according to claim 2, having the following features.

4. The photovoltaic cell according to any one of claims 1 to 3, wherein the metallocene is ferrocene.

5. R １ However, the basis of equation (II): -A-B (II) In the formula, A is a divalent group containing O, S, N, or P; B is H, C １－１２ The alkyl, optionally substituted aryl, or optionally substituted heteroaryl; The photovoltaic battery according to any one of claims 1 to 3.

6. A is the formula: -(R ５ ) ｆ -Z-(R ５ )g-(III) -(R ６ O) ｊ - (IV) During the ceremony: R ５ However, in each event, it is independently a hydrocarbon group; f and g are independently either 0 or 1; R ６ However, it is a C1-4 alkylene group, preferably ethylene; j is between 1 and 10; Z is O, S, COO, C(=S)O, C(=O)S, CONR ４ , CSNR ４ , OC(=O)O, OC(=O)NR ４ OC(=O)PR ４ , NR ４ PR ４ , -OP(=O)(OR ４ )-O-,-NR ４ -P(=O)(NR ４ ２ ) - NR ４ - and R ４ However, H may be optionally substituted for C. １－１２ It is an alkyl or optionally substituted phenyl; A photovoltaic cell according to claim 5, selected from the following bases.

7. The photovoltaic cell according to claim 5, wherein A is -O-C (=O)-.

8. The photovoltaic cell according to claim 5, wherein B is selected from phenyl which may be optionally substituted and a five-membered heteroaryl which may be optionally substituted and comprising one or more ring atoms selected from O, S, and N.

9. The photovoltaic cell according to claim 5, wherein B is a thiophene which may be optionally substituted.

10. The perovskite layer is defined by the formula CatPbX ３ or CatSnX ３ A photovoltaic cell according to any one of claims 1 to 3, comprising a perovskite, wherein Cat is a metal cation, an organic cation, or a combination thereof, and X is selected from at least one of I, Br, and Cl.

11. The photovoltaic battery according to any one of claims 1 to 3, wherein the electron transport layer comprises fluorene.

12. A photovoltaic module comprising a plurality of photovoltaic batteries according to any one of claims 1 to 3, wherein the photovoltaic batteries are connected in series.

13. Equation (I): [metallocene] p (I) During the ceremony: Metallocenes have two aromatic or heterocyclic aromatic groups Ar １ It is a metallocene group containing a metal bonded to it; p is at least 1; At least one metallocene has at least one substituent R １ It is replaced by, R １ Equation (II): -A-B (II) In the formula, A is a divalent group containing O, S, N, or P; B is an aryl or heteroaryl which may be optionally substituted; It is the basis of; A compound of [unclear].

14. The compound according to claim 13, wherein Ar1 may be optionally substituted with a cyclopentadienyl.

15. The compound according to claim 13, wherein the metallocene is ferrocene.

16. A is the formula: -(R ５ ) ｆ -Z-(R ５ )g-(III) -(R ６ O) ｊ - (IV) During the ceremony: R ５ However, in each event, it is independently a hydrocarbon group; f and g are independently either 0 or 1; R ６ However, it is a C1-4 alkylene group, preferably ethylene; j is between 1 and 10; Z is O, S, COO, C(=S)O, C(=O)S, CONR ４ , CSNR ４ , OC(=O)O, OC(=O)NR ４ OC(=O)PR ４ , NR ４ PR ４ , -OP(=O)(OR ４ )-O-,-NR ４ -P(=O)(NR ４ ２ ) - NR ４ - and R ４ However, H may be optionally substituted for C. １－１２ It is an alkyl or optionally substituted phenyl; A compound according to any one of claims 13 to 15, selected from the groups.

17. The compound according to claim 16, wherein A is -O-C(=O)-.

18. The compound according to any one of claims 13 to 15, wherein B is selected from a phenyl which may be optionally substituted and a five-membered heteroaryl which may be optionally substituted and which comprises one or more ring atoms selected from O, S, and N.

19. The compound according to claim 18, wherein B is a thiophene which may be optionally substituted.

Images