TRIPLE-JUNCTION ALL-PEROVSKITE PHOTOVOLTAIC DEVICE AND METHODS OF MAKING THE SAME

Abstract

The present invention provides a triple-junction photovoltaic device comprising three photoactive regions, each photoactive region comprising a perovskite material. A second sub-cell is comprised of a photoactive perovskite layer deposited directly onto a first sub-cell comprising a photoactive perovskite layer, creating a monolithically integrated device with two external electrical contacts (2T). A third sub-cell comprising a photoactive perovskite layer, engineered independently with two external electrical contacts, is stacked onto the second sub-cell of the monolithically integrated device, creating a novel triple-junction all-perovskite photovoltaic device with four external electrical contacts (4T). Also provided is a method of constructing a triple-junction all-perovskite photovoltaic device with four external electrical contacts and a method for perovskite material formation comprising inclusion of the organic stress-inducing compounds metformin and berberine to enhance perovskite crystal formation, stability, and perovskite solar cell efficiency.

Claims

1. A triple-junction all-perovskite photovoltaic device comprising: a first transparent conducting oxide (TCO) substrate; a first electron-transport layer (ETL) located on top of the first TCO substrate; a first perovskite halide film located on top of the first ETL; a first hole-transport layer (HTL) located on top of the first perovskite halide film; a second ETL located on top of the first HTL; a second perovskite halide film located on top of the second ETL; a second HTL located on top of the second perovskite halide film; a transparent conducting polymer layer located on top of the second HTL; a second TCO substrate located on top of the transparent conducting polymer; a third ETL located on top of the second TCO substrate; a third perovskite halide film located on top of the third ETL; a third HTL located on top of the third perovskite halide film; and a metal layer located on top of the third HTL.

2. The device of claim 1, wherein the first TCO substrate consists of fluorine-doped tin oxide (FTO)-coated glass, wherein the first TCO substrate has an external electrical contact attached, and wherein the first TCO substrate is located on the surface of the device that is exposed to sunlight.

3. The device of claim 1, wherein the first ETL consists of zinc oxide (ZnO), and wherein the first ETL has a width greater than or equal to 40 nanometers but less than or equal to 50 nanometers.

4. The device of claim 1, wherein the first photoactive region consists of a perovskite material of the formula ABX.sub.3 wherein A is a methylammonium cation (CH3NH3+), B is a lead cation (Pb2+), and X is iodide (I), wherein the first photoactive region has a bandgap approximately equal to 1.6 electron volts, and wherein the first photoactive region has a width greater than or equal to 800 nanometers but less than or equal to 900 nanometers.

5. The device of claim 1, wherein the first HTL consists of the polymer poly(triarylamine) (PTAA), and wherein the first HTL has a width greater than or equal to 200 nanometers but less than or equal to 300 nanometers.

6. The device of claim 1, wherein the second ETL consists of zinc oxide (ZnO), and wherein the second ETL has a width greater than or equal to 40 nanometers but less than or equal to 50 nanometers.

7. The device of claim 1, wherein the second photoactive region consists of a perovskite material of the formula ABX.sub.3 wherein A is a formamidinium cation (NH.sub.2CHNH.sub.2.sup.+), B is a lead cation (Pb.sup.2+), and X is iodide (I.sup.), wherein the second photoactive region has a bandgap approximately equal to 1.48 electron volts, and wherein the second photoactive region has a width greater than or equal to 1,300 nanometers but less than or equal to 1,400 nanometers.

8. The device of claim 1, wherein the second HTL consists of the polymer poly(triarylamine) (PTAA), and wherein the second HTL has a width greater than or equal to 200 nanometers but less than or equal to 300 nanometers.

9. The device of claim 1, wherein the transparent conducting polymer layer has an external electrical contact attached, wherein the transparent conducting polymer layer consists of the polymer poly(3-hexylthiophene) (P3HT), and wherein the transparent conducting polymer layer has a width greater than or equal to 300 nanometers but less than or equal to 400 nanometers.

10. The device of claim 1, wherein the second TCO substrate consists of fluorine-doped tin oxide (FTO)-coated glass, and wherein the second TCO substrate has an external electrical contact attached.

11. The device of claim 1, wherein the third ETL consists of zinc (ZnO), and wherein the third ETL has a width greater than or equal to 40 nanometers but less than or equal to 50 nanometers.

12. The device of claim 1, wherein the third photoactive region consists of a perovskite material of the formula A.sub.1-yA.sub.yB.sub.1-zB.sub.zX.sub.3 wherein A is a methylammonium cation (CH.sub.3NH.sub.3.sup.+), A is a formamidinium cation (NH.sub.2CHNH.sub.2.sup.+), B is a lead cation (Pb.sup.2+), B is a tin cation (Sn.sup.2+), and X is iodide (I.sup.) and the value of y is equal to 0.5 and the value of z is equal to 0.25, wherein the third photoactive region has a bandgap approximately equal to 1.33 electron volts, and wherein the third photoactive region has a width greater than or equal to 1,500 nanometers but less than or equal to 1,600 nanometers.

13. The device of claim 1, wherein the third HTL consists of the polymer poly(triarylamine) (PTAA), and wherein the third HTL has a width greater than or equal to 200 nanometers but less than or equal to 300 nanometers.

14. The device of claim 1, wherein the metal layer consists of silver (Ag), and wherein the metal layer has an external electrical contact attached to it.

15. The device of claim 1 wherein the triple-junction all-perovskite photovoltaic device is encapsulated in a thin, plastic material comprising polyimide.

16. A method for manufacturing a triple junction all-perovskite photovoltaic device with four external electrical contacts, the method comprising: placing a perovskite-based single junction photovoltaic device with two external electrical contacts on top of a monolithically fabricated all-perovskite multi-junction photovoltaic device with two external electrical contacts, and wherein the transparent conducting oxide substrate of the perovskite-based single junction photovoltaic device is deposited on top of and makes contact with the transparent conducting polymer layer of the monolithically fabricated all-perovskite multi-junction photovoltaic device.

17. The method of claim 16, wherein the perovskite-based single junction photovoltaic device with two external electrical contacts comprises: a transparent conducting oxide substrate with an external electrical contact attached; an electron-transport layer deposited on top of the transparent conducting oxide substrate; a perovskite halide film deposited on top of the electron-transport layer; a hole-transport layer deposited on top of the perovskite halide film; and a metal layer with an external electrical contact attached deposited on top of the hole-transport layer.

18. The method of claim 16, wherein the monolithically fabricated all-perovskite multi-junction photovoltaic device with two external electrical contacts comprises: a first transparent conducting oxide substrate with an external electrical contact attached; a first electron-transport layer deposited on top of the first transparent conducting oxide substrate; a first perovskite halide film deposited on top of the first electron-transport layer; a first hole-transport layer deposited on top of the first perovskite halide film; a second electron-transport layer deposited on top of the first hole-transport layer; a second perovskite halide film deposited on top of the second electron-transport layer; a second hole-transport layer deposited on top of the second perovskite halide film; and a transparent conducting polymer layer with an external electrical contact attached deposited on top of the second hole-transport layer.

19. A method of forming a perovskite halide thin film, the method comprising: forming and depositing a perovskite precursor solution onto a substrate, wherein the perovskite precursor solution comprises: (i) 1,8-diiodooctane (DIO) 5 vol %; (ii) 7 mg mL.sup.1 of metformin; (iii) 9 mg mL.sup.1 of berberine; (iv) Methylammonium (CH.sub.3NH.sub.3.sup.+); (v) Lead (Pb.sup.2+); and (vi) Iodide (I.sup.).

20. The method of claim 19, wherein the perovskite precursor solution comprises: (i) 1,8-diiodooctane (DIO) 5 vol %; (ii) 7 mg mL.sup.1 of metformin; (iii) 9 mg mL.sup.1 of berberine; (iv) Formamidinium (NH.sub.2CHNH.sub.2.sup.+); (v) Lead (Pb.sup.2+); and (vi) Iodide (I.sup.).

21. The method of claim 19, wherein the perovskite precursor solution comprises: (i) 1,8-diiodooctane (DIO) 5 vol %; (ii) 7 mg mL.sup.1 of metformin; (iii) 9 mg mL.sup.1 of berberine; (iv) Methylammonium (CH.sub.3NH.sub.3.sup.+); (v) Formamidinium (NH.sub.2CHNH.sub.2.sup.+); (vi) Lead (Pb.sup.2+); (vii) Tin (Sn.sup.2+); and (viii) Iodide (I.sup.).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1a illustrates schematically a perovskite-based single junction photovoltaic device, according to embodiments of the present invention.

[0025] FIG. 1b illustrates schematically a monolithically fabricated all-perovskite multi-junction photovoltaic device, according to embodiments of the present invention.

[0026] FIG. 2 illustrates schematically a triple-junction all-perovskite photovoltaic device, according to embodiments of the present invention.

[0027] FIG. 3 illustrates a schematic of a method of forming a perovskite halide thin film, according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0028] FIG. 1a illustrates schematically a perovskite-based single junction photovoltaic device 100a, according to embodiments the present invention. In FIG. 1a, 100a comprises a transparent conducting oxide (TCO) substrate 101, an electron transport layer (ETL) 102, a photoactive region 103, a hole transport layer (HTL) 104, a metal electrode 105, and two external electrical contacts 114 and 115.

[0029] In FIG. 1a, the device 100a comprises a TCO substrate 101, wherein the TCO substrate 101 consists of fluorine-doped tin oxide (FTO)-coated glass. An external electrical contact 115 is attached to the TCO substrate 101. An ETL 102 is located on top of the FTO-coated glass layer 101, wherein the ETL 102 consists of zinc oxide (ZnO). The ETL 102 consisting of ZnO has a width (x) of greater than or equal to 40 nanometers (nm) but less than or equal to 50 nm (40 nmx50 nm). A photoactive region 103 is located on top of the ETL 102, wherein the photoactive region 103 consists of a perovskite material of the formula A.sub.1-yA.sub.yB.sub.1-zB.sub.zX.sub.3, wherein A is a methylammonium cation (CH.sub.3NH.sub.3.sup.+), A is a formamidinium cation (NH.sub.2CHNH.sub.2.sup.+), B is a lead cation (Pb.sup.2+), B is a tin cation (Sn.sup.2+), and X is iodide (I.sup.), with the value of y equal to 0.5 and the value of z equal to 0.25 (MA.sub.0.5FA.sub.0.5 Pb.sub.0.75 Sn.sub.0.25 I.sub.3). The photoactive region 103 has a width (x) of greater than or equal to 1,500 nm but less than or equal to 1,600 nm (1,500 nmx1,600 nm). An HTL 104 is located on top of the photoactive region 103, wherein the HTL 104 consists of the polymer poly(triarylamine) (PTAA). The HTL 104 consisting of PTAA has a width (x) of greater than or equal to 200 nm but less than or equal to 300 nm (200 nmx300 nm). A metal electrode 105 is located on top of the HTL 104, wherein the metal electrode 105 consists of silver (Ag). An external electrical contact 114 is attached to the metal electrode 105.

[0030] FIG. 1b illustrates a monolithically fabricated all-perovskite multi-junction photovoltaic device 100b, according to the present invention. In FIG. 1b, 100b comprises a transparent conducting oxide (TCO) substrate 106, a first ETL 107, a first photoactive region 108, a first HTL 109, a second ETL 110, a second photoactive region 111, a second HTL 112, a transparent conducting polymer layer 113, and two external electrical contacts 116 and 117.

[0031] In FIG. 1b, the device 100b comprises a TCO substrate 106, wherein the TCO substrate 106 consists of fluorine-doped tin oxide (FTO)-coated glass. The TCO substrate 106 will function as a front electrode located on the surface of the device that is exposed to sunlight. An external electrical contact 117 is attached to the TCO substrate 106. A first ETL 107 is located on top of the FTO-coated glass layer 106, wherein the first ETL 107 consists of zinc oxide (ZnO). The first ETL 107 consisting of ZnO has a width (x) of greater than or equal to 40 nm but less than or equal to 50 nm (40 nmx50 nm). A first photoactive region 108 is located on top of the first ETL 107, wherein the first photoactive region 108 consists of a perovskite material of the formula ABX.sub.3, wherein A is a methylammonium cation (CH.sub.3NH.sub.3.sup.+), B is a lead cation (Pb.sup.2+), and X is iodide (I.sup.) (MAPbI.sub.3). The first photoactive region 108 has a width (x) of greater than or equal to 800 nm but less than or equal to 900 nm (800 nmx900 nm). A first HTL 109 is located on top of the first photoactive region 108, wherein the first HTL 109 consists of the polymer poly(triarylamine) (PTAA). The first HTL 109 consisting of PTAA has a width (x) of greater than or equal to 200 nm but less than or equal to 300 nm (200 nmx300 nm). A second ETL 110 is located on top of the first HTL 109, wherein the second ETL 110 consists of zinc oxide (ZnO). The second ETL 110 consisting of ZnO has a width (x) of greater than or equal to 40 nm but less than or equal to 50 nm (40 nmx50 nm). A second photoactive region 111 is located on top of the second ETL 110, wherein the second photoactive region 111 consists of a perovskite material of the formula ABX.sub.3, wherein A is a formamidinium cation (NH.sub.2CHNH.sub.2.sup.+), B is a lead cation (Pb.sup.2+), and X is iodide (I.sup.) (FAPbI.sub.3). The second photoactive region 111 has a width (x) of greater than or equal to 1,300 nm but less than or equal to 1,400 nm (1,300 nmx1,400 nm). A second HTL 112 is located on top of the second photoactive region 111, wherein the second HTL 112 consists of the polymer poly(triarylamine) (PTAA). The second HTL 112 consisting of PTAA has a width (x) of greater than or equal to 200 nm but less than or equal to 300 nm (200 nmx300 nm). A transparent conducting polymer layer 113 is located on top of the second HTL 112, wherein the transparent conducting polymer layer 113 consists of the polymer poly(3-hexylthiophene) (P3HT). The transparent conducting polymer layer 113 consisting of P3HT has a width (x) of greater than or equal to 300 nm but less than or equal to 400 nm (300 nmx400 nm). An external electrical contact 116 is attached to the transparent conducting polymer layer 113.

[0032] FIG. 2 illustrates schematically a triple-junction all-perovskite photovoltaic device with four external electrical contacts, according to embodiments of the present invention. In FIG. 2, the device 200 is manufactured by placing the perovskite-based single junction photovoltaic device 100a on top of the monolithically fabricated all-perovskite multi-junction photovoltaic device 100b, wherein the wherein the TCO substrate 101 of device 100a makes contact with the transparent conducting polymer layer 113 of device 100b.

[0033] In FIG. 2 the device 200 comprises a first TCO substrate 201, wherein the TCO substrate 201 consists of fluorine-doped tin oxide (FTO)-coated glass. The TCO substrate 201 will function as a front electrode located on the surface of the device that is exposed to sunlight. An external electrical contact 214 is attached to the TCO substrate 201. A first ETL 202 is located on top of the first FTO-coated glass layer 201, wherein the first ETL 202 consists of zinc oxide (ZnO). The first ETL 202 consisting of ZnO has a width (x) of greater than or equal to 40 nm but less than or equal to 50 nm (40 nmx50 nm). A first photoactive region 203 is located on top of the first ETL 202, wherein the first photoactive region 203 consists of a perovskite material of the formula ABX.sub.3, wherein A is a methylammonium cation (CH.sub.3NH.sub.3.sup.+), B is a lead cation (Pb.sup.2+), and X is iodide (I.sup.) (MAPbI.sub.3). The first photoactive region 203 has a width (x) of greater than or equal to 800 nm but less than or equal to 900 nm (800 nmx900 nm). A first HTL 204 is located on top of the first photoactive region 203, wherein the first HTL 204 consists of the polymer poly(triarylamine) (PTAA). The first HTL 204 consisting of PTAA has a width (x) of greater than or equal to 200 nm but less than or equal to 300 nm (200 nmx300 nm). A second ETL 205 is located on top of the first HTL 204, wherein the second ETL 205 consists of zinc oxide (ZnO). The second ETL 205 consisting of ZnO has a width (x) of greater than or equal to 40 nm but less than or equal to 50 nm (40 nmx50 nm). A second photoactive region 206 is located on top of the second ETL 205, wherein the second photoactive region 206 consists of a perovskite material of the formula ABX.sub.3, wherein A is a formamidinium cation (NH.sub.2CHNH.sub.2.sup.+), B is a lead cation (Pb.sup.2+), and X is iodide (I.sup.) (FAPbI.sub.3). The second photoactive region 206 has a width (x) of greater than or equal to 1,300 nm but less than or equal to 1,400 nm (1,300 nmx1,400 nm). A second HTL 207 is located on top of the second photoactive region 206, wherein the second HTL 207 consists of the polymer poly(triarylamine) (PTAA). The second HTL 207 consisting of PTAA has a width (x) of greater than or equal to 200 nm but less than or equal to 300 nm (200 nmx300 nm). A transparent conducting polymer layer 208 is located on top of the second HTL 207, wherein the transparent conducting polymer layer 208 consists of the polymer poly(3-hexylthiophene) (P3HT). The transparent conducting polymer layer 208 consisting of P3HT has a width (x) of greater than or equal to 300 nm but less than or equal to 400 nm (300 nmx400 nm). An external electrical contact 215 is attached to the transparent conducting polymer layer 208.

[0034] A second TCO substrate 209 is located on top of the transparent conducting polymer layer 208, wherein the TCO substrate 209 consists of fluorine-doped tin oxide (FTO)-coated glass. An external electrical contact 216 is attached to the TCO substrate 209. A third ETL 210 is located on top of the FTO-coated glass layer 209, wherein the third ETL 210 consists of zinc oxide (ZnO). The third ETL 210 consisting of ZnO has a width (x) of greater than or equal to 40 nm but less than or equal to 50 nm (40 nmx50 nm). A third photoactive region 211 is located on top of the third ETL 210, wherein the third photoactive region 211 consists of a perovskite material of the formula A.sub.1-yA.sub.yB.sub.1-zB.sub.zX.sub.3, wherein A is a methylammonium cation (CH.sub.3NH.sub.3.sup.+), A is a formamidinium cation (NH.sub.2CHNH.sub.2.sup.+), B is a lead cation (Pb.sup.2+), B is a tin cation (Sn.sup.2+), and X is iodide (I.sup.), with the value of y equal to 0.5 and the value of z equal to 0.25 (MA.sub.0.5 FA.sub.0.5 Pb.sub.0.75 Sn.sub.0.25 I.sub.3). The third photoactive region 211 has a width (x) of greater than or equal to 1,500 nm but less than or equal to 1,600 nm (1,500 nmx1,600 nm). A third HTL 212 is located on top of the third photoactive region 211, wherein the third HTL 212 consists of the polymer poly(triarylamine) (PTAA). The third HTL 212 consisting of PTAA has a width (x) of greater than or equal to 200 nm but less than or equal to 300 nm (200 nmx300 nm). A metal electrode 213 is located on top of the third HTL 212, wherein the metal electrode 213 consists of silver (Ag). An external electrical contact 217 is attached to the metal electrode 213.

[0035] The triple-junction all-perovskite photovoltaic device with four external electrical contacts 200 is also encapsulated in a thin, plastic birefringent coating comprising the polymer polyimide. Although PV devices used in solar panels are most often encapsulated in glass to provide protection from environmental factors, polyimide films have been shown to be 100 times thinner and 200 times lighter than glass used for PV devices (New superstrate material enables flexible, lightweight and efficient thin film solar modules, https://www.sciencedaily.com/releases/2011/06/110609084806.htm, last accessed, Aug. 18, 2019). Polyimide films are lightweight and flexible, exhibit high resistance to heat and chemicals, and are used in thermal blankets on spacecraft for protection from extreme heat and cold in deep space (Extreme Versatility and Thermal Performance Provides Unlimited Potential, https://www.dupont.com/electronic-materials/polyimide-films.html, last accessed, Aug. 18, 2019). Polyimide thin films also exhibit birefringence (i.e. the refraction of light when passing from one medium to another), potentially enhancing absorption of high-energy photons in PV solar cell devices, leading to an increase in power conversion efficiencies (PCE) (Lee C, Seo J, Shul Y, Han H. Optical Properties of Polyimide Thin Films. Effect of Chemical Structure and Morphology. Polymer Journal 35, 578-585 (2003)).

[0036] FIG. 3 illustrates a schematic of a method of forming a perovskite halide thin film, according to embodiments of the present invention. In FIG. 3, 300a, 300b, and 300c, each comprises a method of forming a perovskite halide thin film, wherein each method comprises a perovskite precursor solution. The perovskite precursor solutions comprising methods 300a, 300b, and 300c, each consist of specific quantities of the biguanide metformin, the isoquinoline alkaloid berberine, and the additive 1,8-diiodooctane (DIO). As noted above, beneficial levels of reactive oxygen species (ROS) increase the stability and efficiency of perovskite solar cells and are also critical for human reproduction, learning and memory formation, and efficient immune system regulation. The biguanide metformin beneficially increases ROS levels in human cells and metformin is also efficacious for the treatment of type 2 diabetes mellitus in human patients (Mogavero A, Maiorana M V, Zanutto S, et al. Metformin transiently inhibits colorectal cancer cell proliferation as a result of either AMPK activation or increased ROS production. Sci Rep. 2017 Nov. 22; 7(1):15992; Sanchez-Rangel E, Inzucchi S E. Metformin: clinical use in type 2 diabetes. Diabetologia. 2017 September; 60(9):1586-1593). The alkaloid berberine also beneficially increases the levels of ROS in human cells and has also shown efficacious results in human clinical trials for the treatment of type 2 diabetes mellitus (Xie J, Xu Y, Huang X, et al. Berberine-induced apoptosis in human breast cancer cells is mediated by reactive oxygen species generation and mitochondrial-related apoptotic pathway. Tumour Biol. 2015 February; 36(2):1279-88; Yin J, Xing H, Ye J. Efficacy of berberine in patients with type 2 diabetes mellitus. Metabolism. 2008 May; 57(5):712-7).

[0037] Additionally, metformin has been shown to facilitate the adsorption of lead (Pb.sup.2+) ions from an aqueous solution, indicating that metformin may enhance and stabilize perovskite crystal formation (Shahabuddin S, Tashakori C, Kamboh M A, et al. Kinetic and equilibrium adsorption of lead from water using magnetic metformin-substituted SBA-15. Environ. Sci.: Water Res. Technol., 2018, 4, 549-558). Berberine has also been shown to be a blue light-absorbing photosensitizer, thus increasing the probability of hot carrier formation in perovskite solar cells, allowing such cells to obtain PCEs that surpass the Shockley-Queisser limit (Siewert B, Vrabl P, Hammerle F, Binggerb I, Stuppner H. A convenient workflow to spot photosensitizers revealed photo-activity in basidiomycetes. RSC Adv., 2019, 9, 4545-4552; Guzelturk B, Belisle R A, Smith M D, et al. Terahertz Emission from Hybrid Perovskites Driven by Ultrafast Charge Separation and Strong Electron-Phonon Coupling. Adv Mater. 2018 March; 30(11)). All-perovskite PV devices that utilize both metformin and berberine to enhance and stabilize perovskite crystal formation for the development and deposition of perovskite halide thin films have not been developed previously or are not currently commercially available.

[0038] In FIG. 3, 300a comprises a method of forming a perovskite halide thin film 302. The method of forming a perovskite halide thin film 302 comprises the formation of a perovskite precursor solution 301, wherein the perovskite precursor solution 301 comprises DIO 5 vol %, 7 mg mL.sup.1 of metformin, 9 mg mL.sup.1 of berberine, and the ions methylammonium (CH.sub.3NH.sub.3.sup.+), lead (Pb.sup.2+), and iodide (I.sup.). After perovskite crystallization and deposition, the perovskite halide thin film 302 formed has the formula ABX.sub.3, wherein A is a methylammonium cation (CH.sub.3NH.sub.3.sup.+), B is a lead cation (Pb.sup.2+), and X is iodide (I.sup.) (MAPbI.sub.3). The perovskite halide thin film 302 has a bandgap (E.sub.g) approximately equal to 1.6 electron volts (eV). 300b comprises a method of forming a perovskite halide thin film 304. The method of forming a perovskite halide thin film 304 comprises the formation of a perovskite precursor solution 303, wherein the perovskite precursor solution 303 comprises DIO 5 vol %, 7 mg mL.sup.1 of metformin, 9 mg mL.sup.1 of berberine, and the ions formamidinium (NH.sub.2CHNH.sub.2.sup.+), lead (Pb.sup.2+), and iodide (I.sup.). After perovskite crystallization and deposition, the perovskite halide thin film 304 formed has the formula ABX.sub.3, wherein A is a formamidinium cation (NH.sub.2CHNH.sub.2.sup.+), B is a lead cation (Pb.sup.2+), and X is iodide (I.sup.) (FAPbI.sub.3). The perovskite halide thin film 304 has a bandgap (E.sub.g) approximately equal to 1.48 electron volts (eV). 300c comprises a method of forming a perovskite halide thin film 306. The method of forming a perovskite halide thin film 306 comprises the formation of a perovskite precursor solution 305, wherein the perovskite precursor solution 305 comprises DIO 5 vol %, 7 mg mL.sup.1 of metformin, 9 mg mL.sup.1 of berberine, and the ions methylammonium (CH.sub.3NH.sub.3.sup.+), formamidinium (NH.sub.2CHNH.sub.2.sup.+), lead (Pb.sup.2+), tin (Sn.sup.2+), and iodide (I.sup.). After perovskite crystallization and deposition, the perovskite halide thin film 306 formed has the formula A.sub.1-yA.sub.yB.sub.1-zB.sub.zX.sub.3, wherein A is a methylammonium cation (CH.sub.3NH.sub.3.sup.+), A is a formamidinium cation (NH.sub.2CHNH.sub.2.sup.+), B is a lead cation (Pb.sup.2+), B is a tin cation (Sn.sup.2+), and X is iodide (I.sup.), with the value of y equal to 0.5 and the value of z equal to 0.25 (MA.sub.0.5 FA.sub.0.5 Pb.sub.0.75 Sn.sub.0.2 I.sub.3). The perovskite halide thin film 306 has a bandgap (E.sub.g) approximately equal to 1.33 electron volts (eV).

[0039] Although the present invention has been described in reference to specific embodiments, the written description and the embodiments described therein are illustrative and do not limit the present invention. Those skilled in the art may recognize modifications or variations to the present invention without departing from the underlying scope and spirit of the present invention and all such modifications or variations are intended to be included in the appended claims.