Moreover, below the transition temperature S value increases with cycling. For example, the room temperature S increases from 90 μV/K for the 1st cycle to 110μV/K for the 3rd cycle, which is due to the decrease in carrier concentration. Eg of Ag2Se is roughly estimated using the relationship between the peak Seebeck coefficient Smax and the corresponding temperature Tmax, that is, Eg=2eSmaxTmax, which is proposed by Goldsmid.[28] Ag2Se has an Eg range between 0.06-0.07eV for cycling three times , which is a little lower than that reported by D. W. Yang et al [11].