Bright Blue Light Emission of Ni2+ ions doped CsPbClxBr3-x Perovskite Quantum Dots Enabling Efficient Light-Emitting Devices.

In recent years, the significant advances with the external quantum efficiency (EQE) over 20% have been achieved in the red and green light-emitting diodes (LEDs) based on perovskite quantum dots (QDs). However, the performances of the blue perovskite LEDs are still seriously lagging behind that of their green and red counterparts. Herein, we successfully developed Ni2+ ions doped CsPbClxBr3-x QDs through the room-temperature supersaturated recrystallization synthetic approach. The innovation of our synthesis rely on the facts that we simultaneously realize the doping of various concentration of Ni2+ cations, as well as modulating the Cl/Br element ratios through introducing the different amount of NiCl2 solution in the reaction medium. By this synthetic method, not only the emission wavelength from 508 to 432 nm of Ni2+ ions doped CsPbClxBr3-x QDs can be facially adjusted, but also the photoluminescence quantum yield (PLQY) of perovskite QDs is greatly improved by the efficiently removing the defect of materials. Thus, the blue emission at 470 nm with PLQY of 89% was achieved in 2.5% Ni2+ ions doped CsPbCl0.99Br2.01 QDs, which is almost three times as much as that of undoped CsPbClBr2 QDs, and is the highest result for the CsPbX3 perovskite QDs with blue emission that fulfilled the NTSC standards. Benefiting the high luminous Ni2+ ions doped perovskite QDs, the blue emitting LED at 470 nm was fabricated exhibiting the EQE of 2.4% and a maximum luminance of 612 cd m-2, which are both higher than the values reported from current reported the best-performing LED based on the blue-emitting CsPbX3 perovskite QDs.