Enhancement of CsPbI3 perovskite solar cells with dual functional passivator 4-Fluoro-3-phenoxybenzaldehyde

Abstract

All-inorganic perovskite CsPbI3 is an attractive light-absorbing layer material owing to its excellent light-absorbing ability and suitable band gap. However, as the research of perovskite progresses, the negative effects of the defect are further revealed. The uncoordinated Pb2+ and I− vacancies within the perovskite film could inevitably lead to irreversible decay in the power conversion efficiency (PCE) as well as environmental instability for perovskite solar cells (PSCs), impeding the their commercialization process and further improvement in photovoltaic performance. Therefore, the new additive 4-Fluoro-3-phenoxybenzaldehyde (PB) containing fluorine and carboxyl groups is introduced as a dual functional passivator within the perovskite film. Under the cooperative passivation by carboxyl groups and fluorine, the optimized CsPbI3 film exhibits denser morphology, lower density of defect states, as well as enhanced carrier transport properties. Ultimately, a high-performance PSC efficiency of 18.01% with enhanced stability is achieved. The optimized CsPbI3 PSC still maintains 80% of original PCE after 1000 h of illumination with no encapsulation. The key to improving device performance is to fabricate the perovskite film with good morphology, large grain size, and low defect by utilizing the dual passivator of PB.