A one-step sol-gel route derived Ag-CuO film as a novel solar selective absorber

A novel one-step sol-gel method to fabricate spectrally selective solar absorber film has been developed. The selectively absorbing film consists of Ag nano-particles grow in a semiconductor matrix of cupric oxide (CuO). The influence of the preparation conditions, i.e. the addition of diethanolamine (DEA) and tetraethylenepentamine (TEPA) and Ag+/Cu2+ molar ratios, on film structure and optical properties were studied. Texture properties (crystallinity, grain size, surface topography) were obtained by using transmission electron microscopy (TEM), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The results showed that the Ag nano-particles derived from TEPA had higher cystallization and better dispersibility, which were more conductive to the intrinsic absorption. Moreover, the heat treatment in the air did not oxidize the metallic Ag with the increased Ag+/Cu2+ molar ratios, but caused the longitudinal agglomeration among the nanoparticles of Ag, thus led to a cone array structure on the film surface and enhanced the intrinsic absorption. The optical properties analysis of the fabricated film revealed a normal solar absorptivity of α=0.850 and low thermal emissivity of ε=0.05. After adding an anti-reflection layer, the absorptivity had been improved to 0.917 while the thermal emittance remained unaltered. Hence Ag-CuO composite could be used as a novel candidate material for solar selective absorber films.