Thermally Regulated Energy Loss in Dion–Jacobson Perovskite Solar Cells

Quasi-2D perovskite solar cells (PSCs), with impressive stability and tunable optoelectronic properties, have become a promising alternative to 3D PSCs. However, the lack of understanding about rationally promoting the film quality of 2D perovskites has significantly undermined their power conversion efficiency (PCE). Herein, a thermally induced crystallization strategy to process the Dion–Jacobson (DJ) 2D perovskite films based on (BDA)(MA)₄Pb₅I₁₆ (n = 5) afforded by thermal treatments is reported, realizing high-quality perovskite films with increased crystallinity and dense structure. The photovoltaic performance of PSCs improved by thermal treatments is found to be mainly attributed to the significantly suppressed nonradiative recombination, more efficient charge generation, and restricted interfacial charge accumulation. As a result, the optimal device processed with thermal treatments produces a high open-circuit voltage of 1.21 V and a PCE of over 17.6% with suppressed energy loss down to 0.42 eV. Moreover, the treated devices without encapsulation show a satisfactory stability with <20% PCE degradation after 1000 h under maximum power point tracking. The demonstrated strategy in this work offers a promising route for the performance enhancement of 2D DJ PSCs toward realistic energy conversion applications.