Colloidal perovskite quantum dots (QDs) or nanocrystals (NCs) with structure of CsPbX3 (X = Cl, Br, I) are promising materials as down-converting phosphors due to their high quantum yield up to >90%, extremely narrow emission band ~15-30 nm, and tunable emission wavelengths of ~410?700 nm via size or composition control. Compared to other QD materials, the optical and electronic properties of perovskite NCs are much more tolerant to defects so highly efficient light- emitting NCs can be easily prepared without carefully removing surface defects. Also, precision size control is not required for obtaining perovskite NCs with narrow emission
