Stable perovskite solar cells with 25.17% efficiency enabled by improving crystallization and passivating defects synergistically†
Abstract
The film quality of a light absorber is the key factor that limits the efficiency and stability of perovskite solar cells (PSCs). Herein, a new ammonium salt of 2-amidinopyrimidine hydrochloride (APC) is introduced into the surface and shallow layer of a perovskite film for further improving the performance of PSCs. The multi-functional groups within APC not only passivate the iodine vacancies (undercoordinated Pb2+ defects) through interaction with pyrimidine N, but also compensate the formamidine (FA) vacancies (undercoordinated I−) via N–H⋯I hydrogen or ionic bonding. APC also finely tunes the crystallization of FA-based perovskite films, resulting in an ultralong photoluminescence lifetime of about 5 μs and a larger carrier diffusion length of more than 4 μm, which is on par with single crystal perovskites. Benefiting from the excellent charge-carrier activities, the champion device delivers an impressive power conversion efficiency (PCE) of 25.17% (certified 24.51%), a notable fill factor of over 84%, and an open-circuit voltage of 1.184 V (the voltage deficit is only 0.37 V). Additionally, the APC treated device demonstrates excellent long-term storage and operational stability. This study will pave a new avenue for improving the perovskite film quality and realizing highly efficient and stable PSCs.