The focus of attention in this study was the choice of material for optically solar selective coatings on the basis of their optical constants, A computer programme which calculates the optical constants, solar absorptance at air mass (AM)-2, alpha, and thermal emittance at 300K, epsilon, of the 200-nm-thick selective coating on the assumption of both the Maxwell Garnett and Bruggeman theories for the metallic volume fraction below and above 0.3 respectively, was used to design the structure of the composite films. Two systems of composite thin films of metal and dielectric were investigated experimentally, fabricated by RF and DC sputter coater and were verified with computer simulations. One system consist of lower refractive index composites such as Ni:SiO2 and the other of higher refractive index composites such as V:Al2O3 in the spectral range of 0.3-20 mum. These films were fabricated on infrared reflective substrates such as nickel plated copper or aluminium. Results of the copper substrates are being presented here. For comparison and verification, tungsten, cobalt and chromium based composites, having different refractive indices, were also investigated which validated the concept of the choice of material in selective coatings. It was observed that high refractive index composites have lower reflective properties by choosing suitable metallic volume fraction in dielectric and antireflection coating. The higher value of the imaginary part of refractive index, k, is responsible for higher absorption by a factor alpha(i) = 4pik/lambda. Solar absorptance of 0.98 and 0.96 was achieved by simulation and experimental findings with less than 0.05 thermal emittance for 200 nm thick composites of V:Al2O3, It results that higher values of both n and k of the material are more suitable in solar selective coatings. (C) 2002 Elsevier Science B.V. All rights reserved.