Understanding the synergistic influence of the propylammonium bromide additive and erbium-doped CsPbI2Br for highly stable inorganic perovskite solar cells

Inorganic cesium lead halide perovskites have gained increasing attention to boost photovoltaic performance and device stability. Nevertheless, the photoactive to photo-inactive phase transition under ambient conditions hampers its further enhancement. Here, we varied various amounts of propylammonium bromide (PABr) additive in the CsPbI2Br perovskite and further varied the erbium (ErCl3)-doped CsPbI2Br (herein CsPb1−nErnI2BrXn) (where X = Cl; 0 ≤ n < 1) perovskite. Further, in the optimized (CsPb0.97Er0.03I2BrCl0.09) composition, we studied the influence of various amounts of the PABr additive. Our results clearly show the PABr additive added film results in high-quality surface morphology, high crystallinity, and decreased trap-state density. Accordingly, our champion CsPb0.97Er0.03I2BrCl0.09 + 2 mg ml−1 PABr (CsEr-PA)-based inorganic perovskite solar cell (IPVSC) device showed 16.74% power conversion efficiency (PCE), which is much higher than that of bare (13.20%) and CsPb0.97Er0.03I2BrCl0.09-based perovskite devices (15.73%). In addition, the CsEr-PA-based IPVSC device revealed increased long-term stability, which maintained 90% of its initial PCE at 65 °C and thermal stress of over 400 h under ambient conditions. These dual stabilization strategies cover a new way to increase the photovoltaic performance of IPVSCs.