Efficient Electroluminescence from Organic Fluorophore-Containing Perovskite Films

Two-dimensional perovskites containing an organic fluorophore can be a unique emitter for light-emitting diodes (LEDs). However, external quantum efficiencies (EQEs) of fluorophore-containing perovskite LEDs reported thus far are still very low. In this study, these are able to boost the EQE to approximate to 10% by choosing an organic fluorophore with appropriate energy levels for the perovskite structure organization. In the fluorophore-containing perovskite LEDs, carrier transport and exciton formation take place in the perovskite's metal halide framework, thereby avoiding the direct formation of nonradiative triplet excitons on the organic fluorophores. Subsequently, the bright triplet excitons formed in the metal halide framework are transferred to form the radiative singlet states of the organic fluorophores, leading to efficient electroluminescence (EL) from the organic fluorophores regularly dispersed inside the perovskite structure. Unexpectedly higher light-outcoupling efficiency, which is caused by the light scattering in the polycrystalline perovskite layer, will be another reason for efficient EL. These findings will contribute toward the fabrication of LED-based products with high performance at a low cost. In light-emitting diodes using an organic fluorophore-containing 2D perovskite as the emitter, carrier transport, and exciton formation take place in the metal halide sheets. Then, the bright triplet excitons formed in the metal halide sheets are transferred to singlet states of the organic fluorophores. With these processes, efficient electroluminescence is observed from the organic fluorophores inside the perovskite. image