Fluorinated graphene quantum dots-induced defect passivation of perovskite film toward stable and efficient perovskite solar cell

Passivation engineering has been considered as an effective strategy to eliminate defects at grain boundaries and interface of perovskite films. Herein, fluorinated graphene quantum dots (FGQDs), as an antisolvent additive, are successfully introduced into perovskite films for defect passivating. FGQDs can regulate the crystallization process of perovskite via chemical bonding with the undercoordinated Pb²⁺. As a result, the high-quality perovskite film with enlarged grain size and reduced defect density can be obtained. FGQDs modified Cs_0.05MA_0.16FA_0.79Pb(I_0.83Br_0.17)₃ device yields a high-power conversion efficiency of 21.74 %, and a higher PCE of 24.12 % is delivered for the device assembled with FA-based perovskite with a composition of Cs_0.05(FA_0.98MA_0.02)_0.95Pb(I_0.98Br_0.02)₃. Due to the excellent hydrophobicity of F atoms, the unencapsulated devices exhibit good long-term stability under 50 % relative humidity condition (85 % efficiency retention after 30 days). Our findings provide a new passivation strategy toward stable and efficient perovskite solar cells.