Deep-blue-emitting CuBr quantum dots (QDs) hold promise as nontoxic and heavy-metal-free optoelectronic materials, yet their efficiency is limited by intrinsic defects. We report Zn doping as an effective strategy to mitigate defect-mediated recombination in CuBr QDs synthesized via an eco-friendly supersaturated recrystallization method under ambient conditions. XRD shows lattice contraction, Rietveld refinement confirms substitutional doping, and XPS verifies Cu⁺/ Zn²⁺ states without secondary phases. HR-TEM analysis reveals uniform 3.46 ± 0.12 nm Zn:CuBr QDs with reduced bandgap, after doping, indicating weaker quantum confinement. The dominant emission peaks appear at 406 nm (Z_f) and 431 nm (Z_(1,2)) under 365 nm excitation. Narrows defect FWHM, elevated band-edge emission, and extends carrier lifetimes, achieving 96.4 % color purity with CIE coordinates (0.1520, 0.0395). These findings demonstrate that Zn doping is a simple, scalable, and environmentally benign strategy for engineering efficient blue-emitting CuBr QDs.