A transparent p-type semiconductor designed via a polarizability-enhanced strongly correlated insulator oxide matrix

Electron-transporting transparent conducting oxides (TCOs) are a commercial reality, however, hole-transporting counterparts are far more challenging because of limited material design. Here, we propose a strategy for enhancing the hole conductivity without deteriorating the band gap (E_g) and workfunction (Φ) by Cu incorporation in a strongly correlated NiWO₄ insulator. The optimal Cu-doped NiWO₄ (Cu_0.185Ni_0.815WO₄) exhibits a resistivity reduction of ∼10⁹ times versus NiWO₄ as well as band-like charge transport with the hole mobility approaching 7 cm² V^-1 s^-1 at 200 K, a deep Φ of 5.77 eV, and E_g of 2.8 eV. Experimental and theoretical data reveal that the strength of the electron correlation in NiWO₄ is unaffected by Cu incorporation, while the promoted polarizability weakens electron-phonon coupling, promoting the formation of large polarons. Quantum dot light-emitting and oxide p/n junction devices incorporating Cu_0.185Ni_0.815WO₄ exhibit remarkable performances, demonstrating that our approach can be deployed to discover new p-type TCOs.