Defect-Driven Thermoelectric Decoupling in Oxygen-Deficient WOx and Tungsten Magnéli Thin Films Grown by PLD: A Review.

This review aims to analyze defect-driven thermoelectric decoupling in pulsed laser deposition (PLD)-grown oxygen-deficient WOx and tungsten Magnéli thin films. While transition metal oxides offer a non-toxic, abundant alternative to conventional thermoelectrics, tungsten oxide stands out due to the profound impact of sub-stoichiometry on its transport properties. We systematically evaluate how ordered oxygen vacancies and crystallographic shear planes transform insulating WO3 into sub-stoichiometric phases exhibiting metallic-like conductivity. Specifically, we analyze how the delocalization of W5d electrons around defect-rich regions induces electronic states near the Fermi level, decoupling the Seebeck coefficient from electrical conductivity. Simultaneously, we discuss how these engineered defect networks and shear planes selectively enhance phonon scattering, drastically suppressing lattice thermal conductivity without hindering electronic transport. By establishing PLD as an effective approach for precise oxygen stoichiometry and defect architecture control, this review highlights the high-temperature potential of tungsten Magnéli phases and outlines future pathways to maximize their thermoelectric figure of merit (ZT).