Ce³⁺-Doping to Modulate Photoluminescence\nKinetics for Efficient CsPbBr₃ Nanocrystals Based Light-Emitting\nDiodes

Abstract

Inorganic perovskite\nCsPbBr₃ nanocrystals (NCs) are\nemerging, highly attractive light emitters with high color purity\nand good thermal stability for light-emitting diodes (LEDs). Their\nhigh photo/electroluminescence efficiencies are very important for\nfabricating efficient LEDs. Here, we propose a novel strategy to enhance\nthe photo/electroluminescence efficiency of CsPbBr₃ NCs\nthrough doping of heterovalent Ce³⁺ ions via a facile hot-injection\nmethod. The Ce³⁺ cation was chosen as the dopant for CsPbBr₃ NCs by virtue of its similar ion radius and formation of\nhigher energy level of conduction band with bromine in comparison\nwith the Pb²⁺ cation to maintain the integrity of perovskite\nstructure without introducing additional trap states. It was found\nthat by increasing the doping amount of Ce³⁺ in CsPbBr₃ NCs to 2.88% (atomic percentage of Ce compared to Pb) the\nphotoluminescence quantum yield (PLQY) of CsPbBr₃ NCs reached\nup to 89%, a factor of 2 increase in comparison with the native, undoped\nones. The ultrafast transient absorption and time-resolved photoluminescence\n(PL) spectroscopy revealed that Ce³⁺-doping can significantly\nmodulate the PL kinetics to enhance the PL efficiency of doped CsPbBr₃ NCs. As a result, the LED device fabricated by adopting Ce³⁺-doped CsPbBr₃ NCs as the emitting layers exhibited\na pronounced improvement of electroluminescence with external quantum\nefficiency (EQE) from 1.6 to 4.4% via Ce³⁺-doping.