Zwitterion additive-assisted crystal growth regulation and defect passivation for high-performance inorganic perovskite solar cells

Inorganic CsPbI2Br perovskites solar cells (PSCs) have attracted extensive interest owing to their outstanding optoelectronic properties. Nevertheless, the undesirable perovskite film quality and severe charge recombination dramatically restrict their performance improvement. Herein, we propose an additive strategy to modulate the CsPbI2Br crystallization process and reduce the defect density by adding 3-(1-pyridinio)-1-propanesulfonate (PPS) zwitterionic molecules into the perovskite precursor solution. The incorporation of PPS zwitterion can not only retard the crystal growth rate of CsPbI2Br with uniform morphology and enlarged grain size, but also effectively passivate defects via interacting with the uncoordinated sites in the perovskite film. In addition, the PPS zwitterion greatly ameliorates the energy level alignments at the interface. Thus, the photogenerated carriers are more efficiently extracted, and the nonradiative recombination is significantly suppressed. With these benefits, the optimized PPS-based CsPbI2Br device delivers a champion efficiency of 16.37% with high open-circuit voltage (V-OC) of 1.302 V in contrast to the pristine device with an inferior efficiency of 14.26% (V-OC of 1.183 V). In addition, the unencapsulated device with PPS presents improved long-term stability by preserving similar to 85% of the initial efficiency after 760 h storage in ambient atmosphere. These findings provided important insights into the additive strategy of using zwitterionic materials for constructing efficient and stable inorganic PSCs.