Investigation of Triple Cation Organo-Metal Halide Perovskite Solar Cells

Abstract

Organic–inorganic hybrid halide perovskites have attracted considerable attentions due to their impressive photovoltaic properties. Record efficiencies in perovskite solar cells (PSCs) have been achieved using as the absorber material a multiple cation/anion perovskite mixing not only methylammonium (MA) and formamidinium (FA), but also the cesium (Cs) cation and iodine (I) and bromine (Br) as anions, materials that have demonstrated good long-term stability. In this study, we have investigated triple cation engineering to improve the quality of the absorber layer through some substitution of formamidinium (FA) and cesium (Cs) for the methylammornium (MA) cation site. The perovskite absorber layer of CsFAMAPb(IBr)3 was fabricated by one-step spin coating method. One of the important things in one-step spin coating towards to obtain high quality CsFAMAPb(IBr)3 layer is an anti-solvent engineering which is dripping to the anti-solvent during spin coating of CsFAMAPb(IBr)3. The properties of CsFAMAPb(IBr)3 absorber layer were found to be strongly influenced by the amount, dispensing speed, and time to spray of anti-solvent solution. Chlorobenzen was used as an anti-solvent solution. The result that the CsFAMAPb(IBr)3 layer appropriately sprayed with chlorobenzen is beneficial to film quality and device efficiency because the nucleation of CsFAMAPb(IBr)3 layer was affected by the anti-solvent engineering, which affected the film crystallite, density, and surface morphology. The CsFAMAPb(IBr)3 layer by optimized 0.3 mL amount of chlorobenzen, 1.28 mL/sec dispensing speed, and 15 second (time to spray after spinning) showed the best efficiency of above 20 % with reproducibility. This research was also supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2019R1A2C4070248).