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: Cs 2 AgBi 1− x In x Cl 6 (0< x <1). The Cs 2 AgBi 0.125 In 0.875 Cl 6 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 Cs 2 AgBi 0.125 In 0.875 Cl 6 nanocrystals and Cs 2 AgBi 0.125 In 0.875 Cl 6 microcrystals can be synthesized by modified hot injection and rapid cooling crystallization, respectively. The size effect of Cs 2 AgBi 0.125 In 0.875 Cl 6 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.