Researchers from the KAUST Solar Center have monitored the impact of compositional changes on the structural organization and photovoltaic properties of perovskite thin films in situ. The team has reached a conclusion that may benefit perovskite solar cells in the future - that changes in composition affect light-harvesting layer crystallization and perovskite solar cell efficiency.
Sequence of fabrication of a perovskite thin film from precursor solution to solid film via the spin-coating deposition process. Image by KAUST
Solar cell performance and stability depend on the morphology of the thin films, especially their ability to crystallize in the so-called photoactive α-phase. Perovskites that contain lead tend to combine various halides, such as the anionic forms of bromine and iodine, with mixtures of methylammonium, formamidinium, cesium and other cations. These have led to record conversion efficiencies and thermal stabilities compared with their single-halide, single-cation analogs. However, these mixed-halide, mixed-cation perovskite films have been characterized only through ex-situ postdeposition techniques. This limits the understanding of the mechanisms that govern their growth from their sol-gel precursor to their solid state and stalls attempts to improve device performance and stability.