Investigations of Defect Physics and Quenching Effect for Optimizing n-type Carrier Concentration in CuWO₄...

As a semiconductor photocatalyst, antiferromagnetic (AFM) CuWO₄ exhibits a weak n-type behavior in experiments, yet the microscopic origins and effective strategies for enhancing its electron concentration (n₀) remain unclear. This study systematically analyzes the self-consistent Fermi level, n₀, 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 (V_O4²⁺), and Cu vacancies (V_Cu^2-) are the dominant intrinsic defects in CuWO₄ across relevant chemical potential ranges; however, the low Cu_i²⁺ and V_O4²⁺ concentrations and compensation by V_Cu^2- result in intrinsically weak n-type conductivity. Moreover, donor (D⁺) and intrinsic defect codoping enhances n₀ only within a narrow optimized chemical potential region (OCPR) under Cu-rich/W-rich/O-poor conditions at 300 K, where the compensation between V_Cu^2- and D⁺ is suppressed. Remarkably, quenching from 800 to 300 K obviously broadens the OCPR by significantly reducing the V_Cu^2- concentration, enabling higher room-temperature n₀ in CuWO₄ with negligible charge compensation and recombination effects. Thus, this study identifies the origins and fundamental bottleneck of weak intrinsic n-type CuWO₄ and provides an experimentally accessible route to obtain higher n-type conductivity in CuWO₄, which could significantly enhance its photocatalytic performance.