Fundamental understanding in the performance-limiting factors of Cs2AgBiBr6-based perovskite photovoltaics

The Lead-free all-inorganic double perovskite Cs2AgBiBr6 is regarded as an attractive alternative to lead-based organic-inorganic counterparts in perovskite solar cells (PSCs) because of the superb durability, nontoxicity and distinct optical properties. Nevertheless, the power conversion efficiencies (PCEs) of Cs2AgBiBr6-based cells are significantly limited by both inherent and external defects in Cs2AgBiBr6 films caused by structural/optical features and fabrication processes, respectively. Thus, it is necessary to conduct a review to enhance fundamental knowledge regarding the decisive performance-limiting factors and relevant performance improvement strategies of Cs2AgBiBr6-based PSCs. Herein, fundamental knowledge of the decisive performance-limiting factors and relevant origins of Cs2AgBiBr6-based PSCs is presented, including inferior sunlight absorption capability, inferior film quality, high defect amount and unsuitable energy level alignment. On this basis, some distinct strategies to improve the PCEs of Cs2AgBiBr6-based cells are proposed such as dye sensitization, band gap regulation, interface control, additive engineering and (anti-)solvent design. Finally, the remaining key problems and future research directions of Cs2AgBiBr6-based PSCs are provided. Our review aims to present important guidance for future research on Cs2AgBiBr6-based PSCs to break the efficiency record.