Surface Reconstruction of Lead-Free Perovskite Cs₂Ag_0.6Na_0.4InCl₆:Bi by Hydroxylation with Blue-Light-Excited...

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 Cs₂Na_0.4Ag_0.6InCl₆ with Bi doping has been successfully achieved by excess KBr coating and ethanol-driven structural reconstruction. Ethanol drives the formation of hydroxylated Cs_2-yK_yAg_0.6Na_0.4In_0.8Bi_0.2Cl_6-yBr_y in the Cs₂Ag_0.6Na_0.4In_0.8Bi_0.2Cl₆@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 Cs₂Ag_0.6Na_0.4In_0.8Bi_0.2Cl₆@16KBr are fabricated. The application of hydroxylated Cs₂Ag_0.6Na_0.4In_0.8Bi_0.2Cl₆@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.