Doping and Photon Induced Defect Healing of Hybrid Perovskite Thin Films: An Approach Towards Efficient Light Emitting Diodes

Here, we demonstrate a simple method to improve photoluminescence and electroluminescent properties of MAPbBr ₃ perovskite thin films by monovalent Cs cation doping and treatment with UV light. It is known that the intermediate species of lead halides, which limits the photoluminescence quantum yield (PLQY) of perovskite thin films, are formed due to the presence of an organic polar solvent. In such cases, coalescence of nanocrystals is unavoidable when the thin-films are thermally annealed to remove the intermediate phases and solvent residues. We find that PbBr ₂ (DMSO)x complexes can effectively tune the morphology, grain boundary, PLQY, and non-radiative loss of perovskite thin films under UV light irradiation. Upon UV exposure, highly uniform MA _0.87 Cs _0.13 PbBr ₃ ultra-thin (45 nm) films with a full surface coverage of neatly packed nanocrystallites are obtained. When these films are integrated into electroluminescent devices, a current efficiency (CE) of 18.71 Cd/A and an external quantum efficiency (EQE) of 5.63% are observed for green perovskite-based light emitting diodes (PeLEDs). These values of CE and EQE are respectively thirty-four and forty-three times higher than those achieved in pure MAPbBr ₃ based devices.