Exploring optimal in situ fabrication conditions to realize core–shell CsPbBr3 QDs with high PLQYs and structural stability by dual-defect passivation†

Core–shell CsPbBr₃ QDs (core–shell M–CsPbBr₃ QDs) with high structural stability and excellent optical properties were developed through dual-defect passivation, with simultaneous application of in situ thiol ligand passivation and a core–shell structure using SiO₂ as a shell. When MPTES was injected immediately before Cs-oleate injection, the formation of by-products (PbS and trigonal-Cs₄PbBr₆ nanocrystals) was suppressed/minimized and effective surface defect passivation was achieved, resulting in defect-less core–shell M–CsPbBr₃ QDs. The thiol group of MPTES effectively passivated uncoordinated Pb²⁺ defects, while the SiO₂ shell formed by the hydrolysis reaction of three silyl ethers inhibited the formation of defects (vacancies) by preventing the penetration of moisture. The core–shell M–CsPbBr₃ QDs exhibited a PLQY of ∼82.9 ± 3.8%, much higher than that of pristine CsPbBr₃ QDs (∼65.3 ± 3.8%). Furthermore, they also showed more than 5 times higher structural stability in DI water compared to pristine CsPbBr₃ QDs. These results demonstrated that the synergistic effect of surface passivation with the thiol group and the core–shell structure can significantly improve the PLQYs and structural stability of CsPbBr₃ QDs.