Photothermoelectric Device Based on Near-Infrared Absorption and Reflection of Transparent Conductive Oxides

A novel transparent photothermoelectric device has been developed, leveraging the advantageous thermoelectric properties of transparent conductive oxide thin films such as aluminium-doped zinc oxide (AZO), and the absorption or reflectance properties of indium thin oxide (ITO) for near-infrared (NIR) radiation. AZO exhibits transmittance exceeding 70% across a broad range of wavelengths (400–2200 nm) and a high Seebeck coefficient (120–150 µV K⁻¹). Through heat treatments between 300 and 500 °C, ITO's NIR absorption is optimized to values above 40% in the 1–1.5 µm range. The optimized thickness of the ITO/Ag/ITO multilayer structure has an 80% reflectance for wavelengths above 1.2 µm. Integrating these two layers on a transparent thermoelectric AZO film creates a thermal gradient induced by infrared (IR) radiation. This gradient results in a photothermal potential that is sensitive to sunlight intensity, with a sensitivity measured at 1.5 mV W⁻¹. This innovation marks a significant advancement in technology, showcasing the potential for transparent devices in smart windows.