Ab initio calculations of structural, optical and thermoelectric properties for CoSb3 and ACo4Sb12 (AÂ =Â La, Tl and Y) compounds

► The structural, optoelectronic and thermoelectric properties of CoSb3 and filled with La, Tl and Y have been investigated. ► The optoelectronic properties and carrier concentration of CoSb3 change with the filling. ► The carrier concentration of the compound also changes with temperature. ► LaCo4Sb12 possesses the highest Seebeck coefficient of all the compounds. ► On the other hand TlCo4Sb12 has the largest thermal conductivity and power factor.