Reduction in thermal conductivity and electrical resistivity in Cu2SnSe3/Cu2Se composite thermoelectric system

•The mole fraction of monoclinic phase decreases with increase in Cu2Se content.•ρ(T) and S(T) obeys variable range hoping model.•Electrical conductivity of composites are observed to be higher than that of the matrix.•The systematic decrease in thermal conductivity with the addition of Cu2Se is attained.