上海科技大学知识管理系统

Dissociation of organic molecules is one critical factor leading to degradation of perovskite solar cells. The much-improved thermal stability of formamidinium (FA) can significantly reduce molecular dissociation; however, FA-based perovskite suffers from high defect density, which affects efficiency and long-term stability. In this work, based on a precise ion-exchange reaction at the grain surface, we fabricate a Cs(0.15)FA(0.85)PbI(3)/Cs(x)FA(1-x)PbI(3) heterostructure with a Cs-rich Cs(x)FA(1-x)PbI(3) quasi-shell structure. The Cs-rich inorganic structure on the perovskite surface increases defect formation energy and reduces defect density, leading to a power conversion efficiency of 20.7%. The encapsulated device maintains 95% of its initial efficiency after 1,000 h of continuous operation, corresponding to a calculated lifetime approaching 2 years. The device can op. erate at 60 degrees C for 250 h and at 85 degrees C for over 3,000 min, which is one of the best operational stabilities for Cs(x)FA(1-x)PbI(3)-based devices.