Highly efficient deep-blue emitting CsPbBr₃ nanoplatelets synthesized via surface ligand-mediated strategy

Two-dimensional (2D) CsPbBr₃ nanoplatelets (NPLs) have attracted great attention as one of promising semiconductor nanomaterials due to their large exciton binding energy and narrow emission spectra. However, the labile ionic and weakly bound surfaces of deep-blue emitting CsPbBr₃ NPLs with wide bandgap result in their colloidal instability, thus degrading their optical properties. It is challenging to obtain deep-blue emitting CsPbBr₃ NPLs with excellent optical properties. In this study, high-quality blue-emitting CsPbBr₃ NPLs with tunable thickness were prepared adopting the DBSA-mediated confinement effect based on the hot-injection method. Thanks to the coordination interaction of - SO₃^- of DBSA ligand and the Pb²⁺ on the surface of the CsPbBr₃ NPLs, as well as the effective passivation of Br vacancy defects on the surface of NPLs by OAm-Br, the obtained pure-blue CsPbBr₃ NPLs and deep-blue CsPbBr₃ NPLs show high photoluminescence quantum yield (PLQY) of 92 % and 81.2 %, respectively. To the best of our knowledge, this is the highest PLQY recorded for deep-blue emitting CsPbBr₃ NPLs with two monolayers [PbBr₆]^4- octahedra. Furthermore, the agglomeration of CsPbBr₃ NPLs due to ligand loss induced by moisture, oxygen, and irradiation was also suppressed by the dual passivation effect of DBSA and OAm-Br. Our work provided a new approach to developing high-performance and stable deep-blue emitting CsPbBr₃ perovskite nanoplatelets.