Tensile Strain Release by Surface Modulation with Amylamine Hydrochloride toward Improved Efficiency and Stability of Perovskite Solar Cells

Residual tensile strain formed on the perovskite film surface during the uncontrolled annealing process is hazardous to the efficiency and stability of perovskite solar cells. Herein, a surface modulation strategy with a long-chain amylamine hydrochloride (AAC) is employed to wide-bandgap perovskite films for releasing the tensile stress. Benefiting from the effective strain regulation and strong passivation interaction of AAC, not only is the compressive-strain perovskite film established with a reduced defect density and an optimized energy level but also the phase segregation is significantly suppressed. Meanwhile, the AAC-modified perovskite film achieves p-to-n-type transformation and regulates the energy level arrangement of the PSCs. Consequently, the optimized device after AAC treatment achieves a superior power conversion efficiency of 21.61%. Moreover, the unencapsulated device exhibits an improved long-term stability, maintaining 85.05% of its initial efficiency for more than 500 h at a relative humidity of 55% and a temperature of 25 °C.