Size effect of lead-free halide double perovskite on luminescence property

Lead-free halide double perovskites have gathered wide scientific interest since they are environmentally friendly and stable. However, compared to the lead perovskites, their optoelectronic properties are compromised. Herein we report a series of bulk lead-free mixed Bi-In halide double perovskites: Cs2AgBi1-xInxCl6 (0<x<1). The Cs2AgBi0.125In0.875Cl6 breaks the parity-forbidden transition and retains direct band gap structure, having warm-white light emission, with photoluminescence quantum efficiency (PLQE) of 70.3%, much higher than the PLQE of reported lead perovskite materials. Its exciton self-trapping dynamics is investigated. Meanwhile, the Cs2AgBi0.125In0.875Cl6 nanocrystals and Cs2AgBi0.125In0.875Cl6 microcrystals can be synthesized by modified hot injection and rapid cooling crystallization, respectively. The size effect of Cs2AgBi0.125In0.875Cl6 is studied on the photoluminescence (PL) property. Additionally, the bulk material exhibits excellent stability on exposure to light, humidity and air for more than 3 months. It is a promising candidate as highly efficient warm white-light emitting material for road lighting.