Mg2+-Assisted Passivation of Surface Defects of Perovskite Polymer Composite Films for White Light-Emitting Diodes

The instability of perovskites is the most critical unsolved problem that limits their practical application. In this work, magnesium oxide (MgO) was introduced into perovskite nanocrystals (PNCs) by the traditional hot injection strategy (HI), resulting in a decrease in the defects PNCs; therefore the photoluminescence quantum yield (PLQY) can be effectively improved. CsPb(Br/I)3-Mg@styrene-ethylene-butylene-styrene (SEBS) composite films were prepared by mixing perovskite nanocrystals and a SEBS toluene solution. Benefiting from the effective protection of the SEBS matrix, the blue light exposure, and thermal and water stability of PNCs are greatly improved. By combining a red composite film with a Ce:YAG phosphor and an InGaN blue chip, the color rendering index (CRI) of the assembled white light-emitting diodes (WLEDs) can exceed 90 (Ra > 90). Additionally, a light-emitting device with a wide color gamut of 128% of the National Television Standards Committee (NTSC) was achieved by combining green and red composite films with blue chips. The stable and flexible composite film will promote the application of PNCs in the field of general lighting applications and thin-film displays.