Transition metal halide-doped, highly stable all-inorganic perovskite nanocrystals for fabrication of white light-emitting diodes

All-inorganic perovskite nanocrystals (NCs) have drawn enormous attention recently for their excellent optoelectronic properties in many fields. However, their poor stability in polar solvents and at high temperatures hinders practical applications. Moreover, PbX2 (X = Cl, Br or I) is employed both as lead and halide precursor in common protocols, which imposes limitations on the precise adjustment of the amount of reaction species and the composition of the final NCs. Here, we demonstrate that transition metal halides (FeX3, CoX2, NiX2, CuX2 and ZnX2; X = Cl, Br or I) can be efficiently used as halide sources, which not only allows efficient control of the amount of halide precursors and emission wavelength, but also significantly improves the stability of NCs. Since the metal ions are mainly doped on the surface of NCs as ligand stabilizers, all excellent optical properties are preserved, such as high photoluminescent quantum yield and narrow full width at half maxima. Finally, by using green-emitting FeBr3-assisted CsPbBr3 NCs and red-emitting BaGe4O9:Eu3+ phosphors as color converters, a warm white light-emitting diode (WLED) device can be fabricated, with the CIE coordinates of (0.3804, 0.3813), the color temperature of 4033 K, and luminous efficiency of 38.89 lm W-1 under a driving current of 20 mA. This device also shows potential applications in backlit displays, with a wide color gamuta National Television System Committee (NTSC) value of 125% and ITU-R Recommendation B.T. 2020 (Rec. 2020) of 95%.