The luminescence properties of CsPbxM1−xBr3 perovskite nanocrystals transformed from Cs4PbBr6 mediated by various divalent bromide MBr2 salts

Abstract

A novel high concentration doping method based on the transformation from Cs₄PbBr₆ nanocrystals (NCs), which reacted with divalent metal bromide MBr₂, to CsPb_xM_1−xBr₃ NCs was developed. Two types of M²⁺ and Zn²⁺ which cannot emit light and Mn²⁺ and Eu²⁺ which can be used as the luminous centres, were chosen to trigger the transformation of Cs₄PbBr₆ NCs to CsPb_xM_1−xBr₃ NCs. CsPb_xZn_1−xBr₃ 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 Mn²⁺ ions CsPb_xMn_1−xBr₃ NCs show different colours of light from green, green-yellow, pink, and orange-red to purple under an excitation of 365 nm. CsPb_xEu_1−xBr₃ NCs were synthesized for the first time, and a weak luminescence around 618 nm from Eu³⁺ was detected in addition to the band edge luminescence of NCs. X-ray photoelectron spectroscopy (XPS) data showed that Zn²⁺, Mn²⁺ and Eu³⁺ (Eu²⁺) 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 Cs₄PbBr₆ can provide a feasible pathway to reduce the lead toxicity of perovskite NCs and expand their applications.