Aqueous phase synthesis of trimethylsulfoxonium lead triiodide for moisture-stable perovskite solar cells

Abstract Organosulfonium cations have attracted growing attention over conventional organoammonium cations for the development of moisture-stable hybrid organic–inorganic metal halide perovskite solar cells (PSCs). Herein, the synthesis of a moisture-stable trimethylsulfoxonium lead triiodide ((CH3)3SOPbI3 or TMSOPbI3) perovskite is described via a two-step solution process in an aqueous medium. The synthesized TMSOPbI3 exhibits a one-dimensional nanorod array with an optical bandgap of 2.30 eV and a hexagonal crystal structure. In addition, the fabricated fluorine-doped tin oxide/compact-TiO2/mesoporous-TiO2/TMSOPbI3/CuSCN/Au PSC device generates a maximum power conversion efficiency (PCE) of 2.23% with a good moisture stability at ambient temperature and relative humidity (50%) with no PCE loss during 336 h and no change in the crystal structure during 50 days. The high moisture stability of the device is attributed to the absence of hydrogen bonding between the trimethylsulfoxonium (TMSO+) cation and the H2O molecules along with strong electrostatic interactions between the TMSO+ and [PbI6]4- polyhedra in the TMSOPbI3. This research has demonstrated that TMSO+ is suitable for fabricating a stable perovskite-like material with good optoelectronic properties and is a promising material for practical applications.