Tailored n value engineering of Dion-Jacobson 2D layers enables efficient and stable perovskite solar cells

Abstract

The formation of a two-dimensional (2D) perovskite on the perovskite surface is one of the most effective defect control approaches in perovskite solar cells (PSCs). To date, in most high-efficiency perovskite devices, surface defect passivation still relies on Ruddlesden-Popper (RP)-based 2D passivation, even though these structures suffer from instability under environmental and operational stressors. Herein, we present a robust Dion-Jacobson (DJ) 2D passivation layer to address the stability limitations of its RP counterparts. We found that the n value of the DJ 2D perovskite could be finely tuned using a precise post-annealing process. By carefully tailoring then value, we were able to overcome the intrinsically low conductivity of the DJ framework and significantly boost hole extraction at the interface. Benefiting from these advances, our optimized device achieved a power conversion efficiency (PCE) of 25.56% (certified 25.59%) while maintaining high stability in both damp-heat and operational-stability tests.