Abstract
In this research, we demonstrated the use of hafnium acetylacetonate (Hfaca) dissolved in ethanol as a buffer layer for perovskite solar cells from non-halide Pb (dehydrated lead acetate) source material. The inverted p-i-n planar heterojunction structure was employed in this work. A one step spin-coating method was used in depositing the perovskite solution before thermal annealing at 90 °C for 5 min to form the perovskite film. Hfaca has been previously used as a buffer layer, but the optimal concentration has not been reported. The optimum concentration of Hfaca was found to be 1.0 mg/ml, resulting in a power conversion efficiency (PCE) of 12.23% corresponding to more than 30% improvement when compared to the control device (phenyl-C61-butyric acid methyl ester/Ag) without Hfaca, which has a PCE of 8.89%. Hfaca as a buffer layer leads to superior stability, retaining about 90% of its original PCE values after 15 days of storage in a glove box, compared to the control device, which retains 70% of the initial PCE value under the same storage.
Highlights
Organic–inorganic lead halide perovskites have attracted growing research interest over the last decade as the most promising materials for photovoltaic applications
hafnium acetylacetonate (Hfaca) as a buffer layer leads to superior stability, retaining about 90% of its original power conversion efficiency (PCE) values after 15 days of storage in a glove box, compared to the control device, which retains 70% of the initial PCE value under the same storage
The methylammonium lead iodide perovskite film (CH3NH3PbI3) used in this study was obtained by the reaction of methylammonium iodide (MAI) with dehydrated lead acetate [Pb(Ac)2] [see Eq (1)] with dimethylformamide (DMF) as the solvent, FIG. 1. (a) Schematic diagram of the inverted planar heterojunction perovskite solar cell architecture with Hfaca, (b) x-ray diffraction (XRD) patterns, and (c) the SEM picture of the perovskite film used in all the devices
Summary
Organic–inorganic lead halide perovskites have attracted growing research interest over the last decade as the most promising materials for photovoltaic applications. This is because of their exceptional advantages such as light-weight, solution processability, tunable bandgap, high diffusion length, high absorption coefficient, flexible manufacturing process, etc.[1,2,3,4] Organic–inorganic lead halide perovskite solar cells (PSCs) have recorded significant success since their first application by Kojima and co-workers, with a power conversion efficiency (PCE) of 3.8% compared to the present record of 25.2%.5,6 Due to their unique properties, several PSC device architectures have been reported over the past few years, such as mesoporous structures and planar architectures; the planar. Inverted planar heterojunction PSCs are composed of transparent conductive oxide [e.g., indium doped tin oxide (ITO)]/hole transport layer [e.g., poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS)]/perovskite layer/electron transport layer [e.g., phenyl-C61-butyric acid methyl ester (PCBM)]/metal electrode.[16,22] This type of architecture requires a buffer layer such as bathocuproine (BCP),[23] zirconium acetylacetonate,[24] titanium acetylacetonate,[25] or hafnium acetylacetonate (Hfaca)[26] between the electron transport layer and the metal electrode to improve the performance of the device. The methylammonium lead iodide perovskite film (CH3NH3PbI3) used in this study was obtained by the reaction of methylammonium iodide (MAI) with dehydrated lead acetate [Pb(Ac)2] [see Eq (1)] with dimethylformamide (DMF) as the solvent,
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