DFT study of Cr and Co doped ZnS for assessing intermediate band states - F.I. Gonzalez-Moreno

Video presentation for VCCA 2026 Ref:197 Intermediate-band semiconductors (IBS) have emerged as promising materials for solar hydrogen devices [1-3]. Among the II-VI semiconductors, zinc sulfide (ZnS) is particularly attractive because of its chemical stability, abundance, and suitable electronic properties. In this work, a theoretical study of the electronic structure of Cr and Co-doped ZnS was conducted using first-principles calculations. Quantum Espresso was used to evaluate the band structure, density of states, and band gap of the materials under study. The calculations predict a direct band gap at the  point of the Brillouin zone for the reference material ZnS, with a value of 3.56 eV. For a deeper analysis, local density of states (LDOS) calculations were performed using the JFEFF code. A spherical cluster of approximately 1000 atoms with a substitution impurity of Cr and Co was employed. Spin-polarized calculations were performed independently for spin up and down. The results revealed that both Cr and Co introduce localized electronic states within the ZnS band gap. In the case of Cr-doping, the intermediate states are distributed at different energies depending on the type of polarization giving rise to well-defined intermediate states within the band gap. Similarly, Co-doping creates electronic levels within the ZnS band gap; however, the spin-down states are located near the valence band, while the spin-up states are shifted towards the conduction band. With both dopants, there is a high intensity of intermediate states compared to the intrinsic contributions of Zn and S, indicating their highly localized nature and strong association with the 3d orbitals of Cr and Co. These findings demonstrate that Cr and Co doping modify the electronic structure of ZnS and promotes the formation of intermediate electronic states, indicating the potential of these systems as candidates for next-generation photovoltaic devices or photoelectrocatalytic hydrogen production.