Researchers at China’s Xi’an Jiaotong University have developed a solar cell based on multiple-cation lead mixed-halide perovskite (MLMP), which reportedly has a stronger moisture resistance compared to cells based on single-halide perovskites.

The team says that mixed halides offer the chance to manufacture more reproducible, thermally stable films with higher crystal qualities. However, these halides also suffer from stability issues due to abundant point defects and dangling bonds at the grain boundary and film surface. In order to address this problem, the scientists turned to interface engineering. They used phosphorus-containing Lewis acid and base molecules such as triphenylphosphine oxide (TPPO), tetraisopropyl methylenediphosphonate (TMPP), and tris (pentafluorophenyl) phosphine (TPFP) in the surface passivation process.

According to their findings, encapsulated cells based on TMPP and TPFP showed the largest enhancements in efficiency and moisture stability, which were achieved through suppressed halide segregation based on an efficient Lewis acid passivation.

The TPFP treatment reportedly offered the best passivation effect due to the interaction of molecules and surface defects. “Its strong surface passivation to halide defects can not only reduce recombination but also suppress phase segregation,” the researchers explained.