First investigation of additive engineering for highly efficient Cs2AgBiBr6-based lead-free inorganic perovskite solar cells

Inorganic lead (Pb)-free Cs2AgBiBr6 double perovskite is one of the most promising light absorbers in perovskite solar cells (PSCs) to solve the instability and Pb toxicity problems of organic–inorganic perovskites. However, the intrinsic and extrinsic defects of Cs2AgBiBr6 films strongly limit the power conversion efficiencies (PCEs) of Cs2AgBiBr6-based PSCs. Herein, the first investigation of additive engineering in Cs2AgBiBr6-based PSCs is reported to achieve an outstanding efficiency. The introduction of guanidinium thiocyanate (GuaSCN) additive effectively controls the nucleation of Cs2AgBiBr6 crystals during the film formation process, improves the perovskite film quality, suppresses the charge carrier recombination, and accelerates the charge extraction simultaneously. Consequently, after optimizing the GuaSCN amount, the device shows a stable PCE of 3.02% under maximum power point tracking (MPPT) condition. Furthermore, the introduction of GuaSCN additive remarkably improves the ambient stability of the devices. This work provides insights on additive engineering for enhancing the efficiency and stability of inorganic Pb-free Cs2AgBiBr6-based PSCs toward future industrialization of this technology.