Ce³⁺-Doping to Modulate Photoluminescence Kinetics for Efficient CsPbBr₃ Nanocrystals Based Light-Emitting Diodes

Inorganic perovskite CsPbBr₃ nanocrystals (NCs) are emerging, highly attractive light emitters with high color purity and good thermal stability for light-emitting diodes (LEDs). Their high photo/electroluminescence efficiencies are very important for fabricating efficient LEDs. Here, we propose a novel strategy to enhance the photo/electroluminescence efficiency of CsPbBr₃ NCs through doping of heterovalent Ce³⁺ ions via a facile hot-injection method. The Ce³⁺ cation was chosen as the dopant for CsPbBr₃ NCs by virtue of its similar ion radius and formation of higher energy level of conduction band with bromine in comparison with the Pb²⁺ cation to maintain the integrity of perovskite structure without introducing additional trap states. It was found that by increasing the doping amount of Ce³⁺ in CsPbBr₃ NCs to 2.88% (atomic percentage of Ce compared to Pb) the photoluminescence quantum yield (PLQY) of CsPbBr₃ NCs reached up to 89%, a factor of 2 increase in comparison with the native, undoped ones. The ultrafast transient absorption and time-resolved photoluminescence (PL) spectroscopy revealed that Ce³⁺-doping can significantly modulate 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 a pronounced improvement of electroluminescence with external quantum efficiency (EQE) from 1.6 to 4.4% via Ce³⁺-doping.