In situ synthesis of ultra-small CsPbBr₃ quantum dots using dodecylbenzenesulfonic acid-ZnBr₂ ligands: enhanced stability and high photoluminescence quantum yields for wide color gamut displays

Dark-blue-emitting perovskite colloidal quantum dots (CsPbBr₃ QDs) are currently limited in next-generation ultra-high-definition displays due to their suboptimal optical performance and instability. This study introduces a ligand-engineering strategy that facilitates the synthesis of monodisperse CsPbBr₃ QDs (2.6 nm in diameter) exhibiting dark-blue emission at 461 nm with a photoluminescence quantum yield (PLQY) of 90.7 %, along with exceptional stability. Mechanistic analysis indicates that the synergistic interaction between dodecyl benzenesulfonic acid (DBSA) and ZnBr₂ drives the performance enhancement: DBSA regulates the nucleation rate and suppresses Ostwald ripening, achieving sub-3 nm quantum confinement, while ZnBr₂ acts as a bifunctional agent, passivating bromide vacancies and enhancing DBSA adsorption on crystal facets. Additionally, CsPbBr₃ QDs exhibit a long lifetime (22.62 ns) and slow bleaching recovery kinetics, suggesting the effective suppression of non-radiative recombination pathways and efficient utilization of excited carriers. Stability assessments show 89 % photoluminescence retention after six months of ambient storage and 65 % intensity retention under continuous UV irradiation (365 nm, 40 mW/cm², 80 min). The implementation of these QDs in white light-emitting diodes (WLEDs) achieves 123.1 % NTSC and 92.6 % Rec. 2020 color gamut coverage, representing improvements of 31 % and 27 % over conventional phosphor-based devices, respectively. This work presents a synergistic ligand-engineering strategy to overcome the efficiency-stability paradox and enable the industrial deployment of perovskite emitters in optoelectronics.