Theoretical understanding on band engineering of Mn-doped lead chalcogenides PbX (X = Te, Se, S).

Electronic structures of Mn-doped PbX (X = Te, Se, S) are investigated by first-principles calculations. It is found that the Mn-doping in PbTe enlarges the band gap and increases the valence bands degeneracy, showing good agreement with experimental measurements. This band adjustment is demonstrated to be from the anti-bonding of Te-p and Mn-d orbitals. Along the series of PbTe-PbSe-PbS, the band modification of Mn-doping undergoes a gradual transition from multiple valence bands type to resonant states type, owing to the downwards shifted anion-p orbitals. This work provides essential understandings on the band engineering of Mn-doped lead chalcogenides thermoelectric materials.