Modulation of Photophysical Properties for Cspbbr₃ Quantum Dots at Room Temperature Using Using O-Xylyl Bisbenzimidazoilium Salt

Cesium lead bromide (CsPbBr₃) quantum dots (QDs) are promising candidates for next-generation optoelectronic devices owing to their high luminescence and tunable bandgaps. Conventional synthesis approaches, however, often require high temperatures and inert conditions, limiting scalability. Here, we report a simple room-temperature synthesis of CsPbBr₃ QDs and demonstrate modulation of their photophysical properties through O-xylyl bisbenzimidazoilium salt surface functionalization. Tauc analysis revealed a direct bandgap of 2.72 eV, confirming strong quantum confinement relative to the bulk. The QDs exhibited bright green emission centered at 515–520 nm with a narrow full width at half maximum, alongside stable emission under varied excitation power. Time-dependent photoluminescence (PL) studies indicated gradual intensity degradation in pristine QDs, whereas O-xylyl bisbenzimidazoilium salt-functionalized QDs retained higher stability under continuous irradiation. Time-resolved PL analysis showed biexponential decay with average lifetimes of 15–20 ns in pristine samples, extended to ~25 ns after O-xylyl bisbenzimidazoilium salt modification, highlighting efficient surface trap passivation. Compared with conventional ligands, O-xylyl bisbenzimidazoilium salt functionality imparted superior photostability, enhanced emission intensity, and prolonged exciton lifetimes. These findings establish O-xylyl bisbenzimidazoilium salt-based passivation as a robust strategy for improving the optical performance and environmental resilience of perovskite quantum dots synthesized under ambient conditions, offering significant potential for scalable optoelectronic applications.