The luminescence properties of CsPbMBr perovskite nanocrystals transformed from CsPbBr mediated by various divalent bromide MBr salts

A novel high concentration doping method based on the transformation from Cs 4 PbBr 6 nanocrystals (NCs), which reacted with divalent metal bromide MBr 2 , to CsPb x M 1− x Br 3 NCs was developed. Two types of M 2+ and Zn 2+ which cannot emit light and Mn 2+ and Eu 2+ which can be used as the luminous centres, were chosen to trigger the transformation of Cs 4 PbBr 6 NCs to CsPb x M 1− x Br 3 NCs. CsPb x Zn 1− x Br 3 NCs maintained high photoluminescence quantum yields (PLQY) (>75%) and had good dispersion in hexane without obvious dissolution or agglomeration after two weeks. By adjusting the reaction temperature, the intrinsic band edge luminescence and the emission of Mn 2+ ions CsPb x Mn 1− x Br 3 NCs show different colours of light from green, green-yellow, pink, and orange-red to purple under an excitation of 365 nm. CsPb x Eu 1− x Br 3 NCs were synthesized for the first time, and a weak luminescence around 618 nm from Eu 3+ was detected in addition to the band edge luminescence of NCs. X-ray photoelectron spectroscopy (XPS) data showed that Zn 2+ , Mn 2+ and Eu 3+ (Eu 2+ ) doping concentrations are up to 80%, 75% and 50%, respectively. We also analysed the doping mechanism and compared the new method with the traditional high temperature injection method. The lead-depleted perovskite NCs transformed from Cs 4 PbBr 6 can provide a feasible pathway to reduce the lead toxicity of perovskite NCs and expand their applications. A novel high concentration doping method, Cs 4 PbBr 6 reacting with MBr 2 (ZnBr 2 , MnBr 2 , EuBr 2 ) and transforming to CsPb x M 1− x Br 3 nanocrystals, was developed.