Gradient band gap perovskite films with multiple photoluminescence peaks

Abstract Inorganic-organic hybrid materials have been used as a promising material for high-efficiency solar cells and light-emitting diodes. Here, we fabricated a multilayer perovskite film CH3NH3PbBr3@CH3NH3PbI3 (MAPbBr3@MAPbI3) with a sandwich structure by means of thermal evaporation of MAPbBr3 and MAPbI3 single crystals on glass substrates. The MAPbBr3@MAPbI3 film with the sandwich structure, which consists of a MAPbBr3 bottom layer, a MAPbI3-xBrx interlayer, and a MAPbI3 top layer, exhibits gradient band gap and multiple photoluminescence peaks. The gradient band gap can be controllably turned to cover almost the entire visible spectrum. Adjusting the mass ratio of MAPbI3/MAPbBr3 can transform the MAPbBr3@MAPbI3 film from a Br rich phase to an I rich phase, and in this way, the PL emission peaks gradually shift from the blue region (543 nm) to the red region (822 nm), respectively. The property of tunable multiple photoluminescence peaks has application potential in white light-emitting diodes. The gradient band gap perovskites may be used in colorful or tandem structure solar cells. We believe that the sandwich structure of the multilayer perovskite film will facilitate the design and development of more perovskite-based devices.