Myab initioelectronic structure calculations inRSn2n-1Te2n, n=16, R = a vacancy, Cd, and In show that when Sn atom is substituted by R, the Density of State (DOS) of the valence and conduction bands get strongly perturbed. There are significant changes near the band gap region. Sn vacancy causes very little change near the bottom of the conduction band DOS whereas there is an increase in the DOS near the top of the valence band. Results for In impurity shows that, unlike PbTe, the deep defect states in SnTe are resonant states near the top of the valence band. In PbTe these deep defect states lie in the band-gap region (act asn-type). This fundamental difference in the position of the deep defect states in SnTe and PbTe explains the experimental anomalies seen in the case of In impurities (act asn-type in PbTe andp-type in SnTe).
Band Tailing and Deep Defect States in CH3NH3Pb(I1–xBrx)3Perovskites As Revealed by Sub-Bandgap Photocurrent
