Solvent-assisted reaction for spontaneous defect passivation in perovskite solar cells

Abstract

Perovskite solar cells have developed rapidly in the past decade. For fabricating highly efficient perovskite solar cells, efforts have been devoted to modulate the nucleation and crystallization processes of perovskite active layers by solvent, antisolvent and additive engineering. However, there is still a need for effective strategies to regulate perovskite nucleation and crystal growth and passivating in situ defects on the surface and at the grain boundaries. Here we introduce 1,4-butane sultone as the second solvent into the perovskite precursor solution to regulate the nucleation of the α-FAPbI₃ layer. The interaction between 1,4-butane sultone and the solute decreases the density of nucleation and inhibits secondary nucleation. At the same time, the ring-opening conversion of 1,4-butane sultone during the annealing process produces 4-chlorobutane-1-sulfonate and 4-iodobutane-1-sulfonate, which effectively passivate the surface defects in the perovskite. As a result, treated n–i–p planar perovskite solar cells attain a power conversion efficiency of 26.5% (certified as 26.2%), with enhanced long-term stability.