Efficient, stable formamidinium-cesium perovskite solar cells and minimodules enabled by crystallization regulation

Formamidinium-cesium (FA-Cs) lead halide has attracted wide interest for enhancing the stability of perovskite solar cells; however, the crystallization of FA-Cs perovskite usually suffers from more complicated intermediate phase transition processes. Herein, we have developed a dual-functional additive consisting of organic ammonium cation and dithiocarbamate anion to regulate the crystallization and defects of the FA-Cs perovskite film. With a synergistic contribution of the cationic and anionic groups, 24.25% efficiency has been achieved in a single cell with excellent operational stability. Under steady-state light illumination and bias voltage, 90% power output of its initial state can still be obtained after 500 h of continuous operation. After enlarging the device from single cell to module, >20.5% efficiency has been realized from a 10.4 cm 2 minimodule by using only an ultralow-cost laser scribing technology. Briefly, this exploitation of cation-anion synergistic effect from dual-functional additives provides more opportunities for promoting the development of perovskite solar cells.