Surface Reconstruction of Lead-Free Perovskite Cs2Ag0.6Na0.4InCl6:Bi by Hydroxylation with Blue-Light-Excited Performance.

Molecular surface reconfiguration strategies have been instrumental to performance improvements of halide perovskite photovoltaic applications in recent years. However, research into the optical properties of the lead-free double perovskite Cs2AgInCl6 on the complex reconstructed surface is still lacking. Here, blue-light excitation in double perovskite Cs2Na0.4Ag0.6InCl6 with Bi doping has been successfully achieved by excess KBr coating and ethanol-driven structural reconstruction. Ethanol drives the formation of hydroxylated Cs2-yKyAg0.6Na0.4In0.8Bi0.2Cl6-yBry in the Cs2Ag0.6Na0.4In0.8Bi0.2Cl6@xKBr interface layer. The hydroxyl group adsorbed on the interstitial sites of the double perovskite structure induces a transfer of local space electrons to the [AgCl6] and [InCl6] octahedral regions, enabling them to be excited with blue light (467 nm). The passivation of KBr shell reduces the non-radiative transition probability of excitons. Blue-light-excited flexible photoluminescence devices based on hydroxylated Cs2Ag0.6Na0.4In0.8Bi0.2Cl6@16KBr are fabricated. The application of hydroxylated Cs2Ag0.6Na0.4In0.8Bi0.2Cl6@16KBr as down-shift layer in GaAs photovoltaic cell module can increase its power conversion efficiency by 3.34%. The surface reconstruction strategy provides a new way to optimize the performance of lead-free double perovskite.