CsPbBr3/Cs4PbBr6 Nanocomposites: Formation Mechanism, Large-scale and Green Synthesis, and Application in White Light-Emitting Diodes

CsPbBr3/Cs4PbBr6 nanocomposites recently were found to yield efficient luminescence. However, the formation mechanism of the nanocomposites is unclear, and large-scale and green synthesis is still challenging. Here, we develop a self-assembly reaction to fabricate CsPbBr3/Cs4PbBr6 nanocomposites efficiently and environmentally friendly. The transmission electron microscopy clearly shows CsPbBr3 nanocrystal is embedded in Cs4PbBr6 matrix, forming a CsPbBr3/Cs4PbBr6 composite structure. In situ characterization reveals that the CsPbBr3/Cs4PbBr6 nanocomposites are formed by a two-step reaction, driven by ion concentration difference. The self-encapsulation and separation of the CsPbBr3 NCs by the host Cs4PbBr6 result in the material exhibiting a high PLQY of 83% and narrow-band emission at 517 nm with a full width at half-maximum of only 21 nm. Further, we fabricate an on-chip white light-emitting diode (LED) using the as-synthesized CsPbBr3/Cs4PbBr6 nanocomposites as a green emitter and red K2SiF6:Mn4+ phosphor on the surface of a blue LED chip. The resulting white LED exhibits a high luminous efficiency of up to 88 lm W–1 at 20 mA with an NTSC value of 131% and Rec. 2020 of 98%.