Gradient Doping for Stress-Relief in Vapor-deposited Perovskite Film to Achieve High-performance p-i-n Perovskite Solar Cells with a 23% Efficiency.

Vapor-deposited p-i-n perovskite solar cells (PSCs) present key advantages such as low cost, excellent stability, low-temperature fabrication, and compatibility with tandem architectures, positioning them as strong contenders for industrial-scale solar applications. However, their power conversion efficiency (PCE) remains lower than that of n-i-p architectures. Herein, a gradient doping strategy to alleviate the stress in vapor-deposited perovskite films is introduced. Gradient chloride doping in the perovskite precursor film effectively slows the crystallization rate at the bottom layer, facilitating uniform crystallization and mitigating residual strain. This method yielded high-quality perovskite films, achieving a PCE of 23.0% for p-i-n PSCs with vapor-deposited perovskite and 21.43% for entirely vapor-deposited PSCs. Additionally, the devices demonstrates outstanding stability, showing negligible performance degradation over 1600 h of nitrogen storage and maintaining 87.3% of their initial PCE after 500 h of maximum power point tracking under 1-sun equivalent illumination at 70% relative humidity. The gradient doping strategy provides valuable insights for advancing large-area and perovskite-textured silicon tandem solar cells.