Efficient and stable white light emission is of great significance for indoor lighting. Traditional white light emitting devices have some disadvantages, such as easy color change and efficiency loss (self-absorption), while single-substrate white light emitting materials can be avoided. Different from the band edge emission fluorescence generated by free carrier recombination, the self-trapping exciton luminescence has the characteristics of spectral bandwidth and stokes displacement. Because the lattice is "soft", the low-dimensional lead-based perovskite material is easy to form self-trapping excitons, showing wide band white light emission. However, lead is toxic and the luminous efficiency of low - dimensional lead - based perovskite is usually low. Recently, some studies have reported non-lead double perovskite materials with self-trapping exciton luminescence, but colloidal nanocrystals with high efficiency and wide band white light emission are rarely seen.