Strongly polarized metal telluride with slight metal precipitation enables excellent long-wave infrared transparent conductive properties

Long-wave infrared transparent conductive films (LITCFs) are crucial for next-generation infrared optoelectronic devices. However, the development of high-performance LITCFs is extremely challenging due to the simultaneous occurrence of charge carrier transport and carrier absorption. To address this problem, we propose a composite design strategy: a strongly polarized metal compound as the transparent matrix phase and a small amount of precipitated metal as the conductivity-enhancing phase. As a proof of concept, we fabricated WTe0.98 films, which possess coexisting WTe2 and a small amount of W phases. Compared with the conventional transparent conductive film ITO (1373.6 S/cm, 27.94%), WTe0.98 demonstrates not only a higher electrical conductivity (1992.0 S/cm) but also a significantly higher long-wave infrared (LWIR) transmittance (67.44%). We find that the high LWIR transmittance of WTe0.98 originates from the high optical dielectric constant of the WTe2 phase. This high dielectric constant is a result of the enhanced electronic polarizability from the strong p–d hybridized interlayer bonding. The high electrical conductivity of WTe0.98 stems from the high carrier concentration provided by the W phase. Therefore, this study solves the bottleneck problem of coordinating conductivity and LWIR transparency through the design of strongly polarized composite materials with a precipitated metal phase.