Rational design of the synergistic effect with lead iodide as the link for improving the efficiency of carbon-based perovskite solar cells

Abstract

Uncontrolled Ostwald maturation is often accompanied by residual lead iodide (PbI₂), which can degrade into elemental lead and severely damage the perovskite device upon exposure to light and radiation, ultimately accelerating device decay. However, PbI₂ also serves as a critical raw material for the formation of a two-dimensional perovskite. Herein, we designed an innovative synergistic passivation strategy that effectively utilized residual PbI₂ generated during Ostwald ripening as a raw material for dimensional engineering, achieving deep passivation for defects and improving the performance of the perovskite device. First, we induced the Ostwald curing process through post-processing the MAI-PbI₂-DMSO mesophase with GUTS (guanidine thiocyanate), achieving maximum grain growth and fewer defects in the thin film. Unfortunately, this also resulted in residual PbI₂ with adverse effects. To eliminate this effect, we further processed the film with BAI (butylamine iodide) in the second step, which not only eliminated residual PbI₂, but also contributed to the formation of the 2D perovskite, optimizing energy level alignment and improving humidity stability. Finally, the successive passivation of defect states resulted in over 10% improvement in photoelectric conversion efficiency for the carbon-based PSCs prepared using the synergistic strategy. This work highlights the effectiveness of a synergistic passivation strategy for improving device performance.