Visible and infrared transparent conductive films with passive cooling capabilities

In order to facilitate radiative cooling in optoelectronic devices, it is necessary to employ infrared (IR) transparent conductive films (TCFs) that permit thermal radiation from internal circuits to pass through. This can be accomplished by using TCFs with a wide transparency range that extends into the far-IR spectrum. We have produced hafnium-doped indium oxide (InHfO) TCFs that have a wide transparency range spanning from 400 nm to 20 & mu;m. These TCFs, with a thickness of 120 nm, exhibit a sheet resistance of approximately 200 & omega;/, high visible relative transmittance (90% at 550 nm, comparable to ITO), and IR transparency (66.9% in the 1.35-20 & mu;m range). By replacing commercial ITO TCFs with InHfO TCFs, we successfully decreased the operating temperature of an enclosed resistor from 65.5 degrees C to 63.6 degrees C, and potentially to 61.1 degrees C via radiative cooling. This decrease corresponds to around 5-10% of the temperature difference between the resistor and room temperature. The InHfO TCFs we have prepared are suitable for a range of applications requiring transparency from the visible to the far-IR spectrum and may open up new avenues for optoelectronic applications.