Researchers from Sichuan University, Zhejiang University, Chinese Academy of Sciences and Guangxi University have reported a nucleation-layer assisted (NLA) strategy that achieves highly oxygen stable quasi-2D Ruddlesden Popper (RP) tin perovskite solar cells by regulating the phase distribution, crystal orientation, and film morphology of the cells, setting a record for oxygen stability in tin perovskite solar cells.
The formation process of the nucleation layer consists of washing off the prepared perovskite film and annealing the residue on the substrate, which produces a new substrate for perovskite film fabrication. Such nucleation layer can transform the subsequently deposited perovskite film from a small-n-value dominated wide phase distribution with random crystal orientation into an intermediate-n-value dominated narrow phase distribution with vertical crystal orientation.
This nucleation layer also improves the perovskite film morphology with highly coadjacent flake-like grains, leading to reduced grain boundaries and pinholes.
The resulting NLA perovskite film shows more efficient carrier transport capability, lower exciton-binding energy, weakened electron-phonon coupling, and significantly decreased oxygen diffusion rate upon oxygen exposure.
Consequently, a quasi-2D RP Sn-based perovskite solar cells with a champion efficiency of 11.18% was obtained. The unencapsulated device preserved 95% of its initial efficiency after a 2700-h oxygen aging test, which the team stated is a record oxygen stability for Sn-based PSCs.
