**3.1 Primal selection protocols**

Cost and toxicity concerns led to less and less use of Se and Cd-like materials. Additionally, increasing interest in conjoint heat-light conversion took some bad heat-conducting materials out from consideration. Selection protocols are becoming more concentrated on thermal, mechanical and opto-electric performance.

Since thermal conductivity, specific heat and thermal diffusivity has always been considered as material intrinsic properties, while absorbance and reflexivity depend on both material and excitation, there was a need of establishing advanced physical parameters bringing these proprieties together.
