Dual-Surface Polydentate Anchoring Enabled Strain Regulation for Stable and Efficient Perovskite Solar Cells

Abstract

Continuous breakthroughs of photoelectric conversion efficiency (PCE) in perovskite solar cells are achieved, but the inherent instability caused by residual tensile strain and interfacial defects remains a major obstacle to their application. In this study, a polydentate ligand-regulated dual-surface stress management strategy for perovskite (PVK) is introduced to eliminate tensile strain and interface defects via multidentate anchoring. 3-amino-5-bromopicolinaldehyde (BD) is employed on the lower surface of PVK, while its −CO, −NH₂, and pyridine functional groups facilitate the bridging of SnO₂ with PVK, alleviating tensile stress and lowering interfacial energy barriers. For the upper surface, the bis−SO₂, pyridine, and bis−CF₃ functional groups of N-(5-Chloro-2-pyridyl) bis(trifluoromethanesulfonimide) (FC) are utilized to increase the ion migration energy barrier through anchoring, which effectively diminishes tensile stress and defects. Besides, −CF₃ also constructs a hydrophobic barrier on the upper surface. Notably, tensile stress successfully transforms into compressive stress based on the dual-surface stress regulation, significantly improving the framework stability of PVK. Consequently, the devices treated with BD and FC achieve an elevated open-circuit voltage of 1.24 V and PCE of 24.70%. The modified device (unencapsulated) maintains 92% of initial PCE after 2000 h in the atmosphere and 91% after 500 h under 85% RH, showcasing enhanced stability.