Understanding the influences of lattice defect evolution on the optical properties of ZnO is of significance. To clarify this, we adopted typical treatments on ZnO using Al–H co-doping and post-annealing, combined with comprehensive characterization (absorption spectrum, Raman scattering, photoluminescence, electronic paramagnetic resonance and positron annihilation). The results reveal that the visible luminescence can arise from the V_O, V_Zn and Al_Zn–O_i defects, while the defect centers responsible for the blue band optical absorption are assigned to ionized Zn_i and V⁺_O. SEM images illustrated that H⁺ implantation diluted the ZnAl₂O₄ second phase, which reaccumulated after O₂ annealing.