Fabrication of Carbon Nanotube/Indium Tin Oxide “Inverse Tandem” Absorbing Coatings with Tunable Spectral Selectivity for Solar–Thermal Applications

We report the fabrication of a new selective “inverse tandem” absorbing coating based on carbon nanotube (CNT)/indium‐tin oxide (ITO) on aluminium (Al) for mid‐temperature solar–thermal application. The CNT layer is formed by spraying and functions as an excellent solar absorber whereas the ITO layer produced on top of the CNTs by sputtering serves as an IR reflector. The effect of the thickness of the ITO on the spectral selectivity of the absorbing coating was investigated. Controlling the thickness of ITO allowed the spectral selectivity of the coating to be tuned. The CNT/ITO solar coatings with optimized thickness of ITO showed excellent spectral selectivity values of absorptance (α) of 0.927 and emittance (ε) of 0.2. The performance of the coatings at high temperature after heating in air in the range of 25–300 °C for different durations was also investigated. The performance and structure of the CNT/ITO coating was also compared with the wet deposition method in which the ITO coating was formed by spraying. Tandem jump: Fabrication of an “inverse tandem” absorbing carbon nanotube coating (CNT/ITO) with excellent spectral selectivity has been demonstrated. The CNT layer, which shows low reflectance in the solar spectrum, functions as an excellent solar absorber and the indium‐tin oxide (ITO) layers, which show higher reflectance in the IR region, function as emittance inhibitors and make the absorbing coating spectrally selective.