Crystallization kinetics modulation for efficient inverted inorganic perovskite solar cells

Inorganic perovskite solar cells (IPSCs), due to their suitable bandgap and superior thermal stability, are ideal candidates for tandem solar cells combined with silicon. However, the development of inorganic perovskite solar cells has been hindered by suboptimal crystallization dynamics that generate detrimental defects in the perovskite lattice. Here, we propose 4-Methoxyphenylphosphonic Acid (4MPA) as a multifunctional additive to address this challenge. PO in 4MPA establish strong coordination with undercoordinated Pb2+, while OH engage in O⋯HO hydrogen bonding interactions with DMSO, effectively weakening the solvent-[PbX6]4− octahedron interaction. This dual functionality facilitates complete and rapid DMA+-to-Cs+ cation exchange while regulating crystallization kinetics, thereby optimizing crystal growth. Furthermore, π-π interactions between benzene rings significantly enhance the moisture resistance of the perovskite layer. The optimized device demonstrates a power conversion efficiency (PCE) of 21.35 %, with unencapsulated devices retaining 93.63 % of their initial efficiency after 200-hour continuous operation under ambient conditions (35 % relative humidity).