Pb 0.8 Sn 0.2 Se thin films: synthesis, sensitization, and properties evolution

The ternary Pb–SnSe thin films were prepared using chemical bath deposition (CBD) and sensitized with iodine. The chemical formula of the films was recognized as Pb 0.8 Sn 0.2 Se, according to the stoichiometric ratio. The films are both centered cubic crystal structure and show preferred orientation in PbSe (200). The optical band gap ( E g ) is found to decrease after sensitization, due to the impurity energy levels created by PbI 2 . The photoelectric performance of the Pb 0.8 Sn 0.2 Se thin films is significantly improved after iodine sensitization. Accordingly, the resistance change rate, i.e., the photoelectric sensitivity is enhanced over 35%, which is over 161% for more than 4 on/off cycles. The density of states (DOS) of Pb 0.8 Sn 0.2 Se is calculated using the first-principle method. The calculation shows that the I dangling bond in sensitized Pb 0.8 Sn 0.2 Se introduces a large DOS inside the band gap and causes the narrowing of the band gap.