Investigations of Defect Physics and Quenching Effect for Optimizing <i>n-</i> type Carrier Concentration in CuWO ₄ Photocatalyst

As a semiconductor photocatalyst, antiferromagnetic (AFM) CuWO₄ exhibits a weak <i>n</i>-type behavior in experiments, yet the microscopic origins and effective strategies for enhancing its electron concentration (<i>n</i>₀) remain unclear. This study systematically analyzes the self-consistent Fermi level, <i>n</i>₀, and dominant intrinsic defect concentrations in CuWO₄ by using spin-polarized density functional theory and thermodynamic equilibrium simulations. The calculated formation energies indicate that Cu interstitials (Cu_i²⁺), O vacancies (<i>V</i>_O4²⁺), and Cu vacancies (<i>V</i>_Cu^2-) are the dominant intrinsic defects in CuWO₄ across relevant chemical potential ranges; however, the low Cu_i²⁺ and <i>V</i>_O4²⁺ concentrations and compensation by <i>V</i>_Cu^2- result in intrinsically weak n-type conductivity. Moreover, donor (<i>D</i>^<i>+</i>) and intrinsic defect codoping enhances <i>n</i>₀ only within a narrow optimized chemical potential region (<i>OCPR</i>) under Cu-rich/W-rich/O-poor conditions at 300 K, where the compensation between <i>V</i>_Cu^2- and <i>D</i>^<i>+</i> is suppressed. Remarkably, quenching from 800 to 300 K obviously broadens the <i>OCPR</i> by significantly reducing the <i>V</i>_Cu^2- concentration, enabling higher room-temperature <i>n</i>₀ in CuWO₄ with negligible charge compensation and recombination effects. Thus, this study identifies the origins and fundamental bottleneck of weak intrinsic <i>n</i>-type CuWO₄ and provides an experimentally accessible route to obtain higher <i>n</i>-type conductivity in CuWO₄, which could significantly enhance its photocatalytic performance.