Disclosed are new compound semiconductors which may be used for solar cells or as thermoelectric materials, and their application. The compound semiconductor may be represented by a chemical formula: InxMyCo4-m-aAmSb12-n-z-bXnTez, where M is at least one selected from the group consisting of Ca, Sr, Ba, Ti, V, Cr, Mn, Cu, Zn, Ag, Cd, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; A is at least one selected from the group consisting of Fe, Ni, Ru, Rh, Pd, Ir and Pt; X is at least one selected from the group consisting of Si, Ga, Ge and Sn; 0