Figure 4

(a) The crystal structure of Cu2SnSe3. (b) The scheme plot of DOS in Cu2SnX3 (X=S, Se), with the bonding characters and the p-type optimal doping range labeled. (c) and (d) are the contour plots of the partial charge density within the p-type optimal doping range of Cu2SnSe3 (−0.2 to −0.3eV) on the Cu–Se–Sn plane,72 and the close-packed Se–Se–Se plane, respectively.71