Realization of blue-emitting CsPb(Br_1-xCl_x)₃ nanocrystals via simultaneous halide exchange and defect passivation...

Halide perovskite nanocrystals are promising materials for optoelectronic devices due to their outstanding opto-electrical properties. However, achieving stable blue emission with high photoluminescence quantum yield remains challenging because of halide segregation and surface defects. Dopamine hydrochloride was used as a bi-functional reagent to simultaneously facilitate both Br⁻/Cl⁻ halide exchange and surface defect passivation. As the post-treatment time increased, the photoluminescence spectrum of CsPb(Br_1-xCl_x)₃ nanocrystals was blue-shifted from ~512 nm to ~478 nm, and photoluminescence quantum yield increased from ~56.4 ± 2.1% to ~75.5 ± 2.9%. The X-ray photoelectron spectroscopy results revealed that metallic Pb⁰ was effectively passivated by dopamine, resulting in the recovery of photoluminescence quantum yield. The reactivity of dopamine hydrochloride was pH-dependent. Under mildly acidic conditions, dopamine hydrochloride did not effectively dissociate to generate Cl⁻ ions, minimizing bandgap change and inhibiting the formation of polydopamine. In contrast, under mildly basic conditions, both Br⁻/Cl⁻ halide exchange and formation of polydopamine proceeded efficiently. The CsPb(Br_1-xCl_x)₃ nanocrystals retained ~59.4% of their initial photoluminescence intensity under moisture exposure, demonstrating superior structural stability. This work demonstrates that dopamine hydrochloride post-treatment enables blue-emitting CsPb(Br_1-xCl_x)₃ nanocrystals with high photoluminescence quantum yield and excellent structural stability through halide exchange and surface defect passivation.