<p>Zinc aluminate (ZnAl₂O₄) is projected as a versatile compound with excellent thermal and chemical stability, which makes it a suitable material in various applications. Motivated by recent experimental observation that doping of Er into ZnAl₂O₄ makes it as a potential phosphor material for bio-imaging, I have investigated the role of Er doping using density functional theory as a tool. I have also investigated the effect of doping with Er into ZnAl₂O₄, aiming to improve its optical behavior to a greater extent. In contrast to the experimental study, the present study revealed that doping of Er is thermodynamically feasible in both the Al and Zn sites, with Al site energetically more favorable. Electronic structure investigation indicates that the presence of Er(4f) impurity states in the band gap region is mainly responsible for the improvement of optical properties of ZnAl₂O₄. Thus, the present study provides valuable insight for further improvement of the luminescence behavior of these types of materials.</p> Graphical abstract <p>The present study revealed that doping of Er is thermodynamically feasible in both the Al and Zn sites, with Al site energetically more favorable. Electronic structure investigation indicates that the presence of Er(4f) impurity states in the midgap region is mainly responsible for the improvement of optical properties of ZnAl₂O₄.</p>