Surface n‑Doped\nMetal Halide Perovskite for\nEfficient and Stable Solar Cells through Organic Chelation

Perovskite solar cells (PSCs) have emerged as a leading\nphotovoltaic\ntechnology due to their high efficiency and low cost. Even though\nthey have developed rapidly since their inception, with efficiencies\nof over 26%, inverted PSCs face challenges such as nonradiative recombination\nand ion migration. Surface treatment, especially the utilization of\norganic compounds, has improved efficiency and stability by optimizing\nthe perovskite–charge transport layer interface. Herein, we\nreport a facile and effective strategy by introducing 2,2′-bipyridyl\nto modify the surface of perovskite, achieving a power conversion\nefficiency of 24.43% with increasing open-circuit voltage and fill\nfactor and good repeatability on multiple devices. We reveal that\nthe 2,2′-bipyridyl molecule can chelate lead ions on the surface\nof perovskite, effectively suppressing nonradiative recombination.\nFurthermore, this modification can induce surficial n-doping to refine\nthe energy level alignment, thereby minimizing charge transport losses.\nAdditionally, the device maintained over 92% of the initial efficiency\nafter 1000 h of operation at the maximum power point under continuous\nillumination. This surface chelation and defect passivation strategy\nemploying 2,2′-bipyridyl offers a promising avenue for exploring\nthe details of potential long-term degradation mechanisms and the\ndevelopment of commercially viable high-performance p-i-n PSCs.