First-principles study of co-doped wurtzite ZnO: insights into carrier dynamics, visible light absorption, and structural properties for solar cell applications

This study investigates the effect of Ga, In, and (Ga, In) doping at 6.125% concentration on the structural, electronic, carrier lifetime, and optical properties of ZnO using density functional theory (DFT). The GGA + U (Generalized Gradient Approximation with On-Site Coulomb Interaction U) approach was employed to correct band gap underestimation, revealing a decrease in band gap from 3.38 eV (pure ZnO) to 3.24 eV (Zn₁₄Ga₂O₁₆), 2.93 eV (Zn₁₄In₂O₁₆), and 3.07 eV (Zn₁₄GaInO₁₆). Formation energy analysis confirmed the thermodynamic stability of the doped structures, while the Fermi level shift into the conduction band indicated n-type behavior. Partial density of states (PDOS) analysis showed significant contributions from Ga-s, In-s, Zn- (p, s), and O-s orbitals, modifying the electronic structure. Effective mass calculations revealed a reduced \({m}_{e}^{*}/{m}_{h}^{*}\) ratio, enhancing carrier lifetime by minimizing recombination. Optical studies demonstrated an increased probability of electron transitions at lower energies and improved visible-light absorption, particularly after (Ga, In) co-doping. These results suggest Zn₁₄GaInO₁₆ as a promising candidate for use in solar cell and optoelectronic devices.