Novel antisolvent-washing strategy for highly efficient carbon-based planar CsPbBr3 perovskite solar cells

All-inorganic CsPbBr3 is attracting tremendous attentions in photovoltaic field due to its superior stability. However, CsPbBr3 perovskite always suffers from a poor crystallinity and film morphology. Many efforts have been paid on the CsBr deposition process to improve the film quality, while few attentions are paid on the crystallization kinetics of the PbBr2 framework film. Here, we demonstrate a novel antisolvent-washing strategy for the PbBr2 film for the first time to fabricate high-quality CsPbBr3 film. This technique has a significant impact on the nucleation and growth of PbBr2 crystals. As-prepared CsPbBr3 films exhibit more homogeneous with higher crystallinity and coverage as well as larger grain sizes compared to those untreated ones. The best-performing antisolvent-treated perovskite solar cell achieves a scanned power conversion efficiency of 8.55%, which is an excellent efficiency for planar CsPbBr3 cells reported yet. This enhancement can be mainly attributed to the more effective charge transport and suppressed non-radiative recombination caused by the reduced defect densities. Moreover, our devices show superb stability when stored in air for 1000 h and upon persistent thermal attack at 80 degrees C. Our work provides a new train of thought for controlling the growth dynamics and film morphology of CsPbBr3 films.