Surface n-Doped Metal Halide Perovskite for Efficient and Stable Solar Cells through Organic Chelation

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