Cuprous sulfide(Cu2S) is a direct band-gap p-type semiconductor with excellent ionic/electronic hybrid conductivity. Although Cu/Cu2S/sulfide or polysulfide system is adopted as counter electrode of quantum-dots-sensitized solar cells(QDSSC), the electrode process is seldom reported. Here, the electrochemical growth of Cu2 S film on a copper(Cu) surface, the redox behaviors of sulfide and polysulfide, and the all-in-solid charge-transfer properties of Cu2 S film are investigated. It is clarified that the copper electrode simultaneously undergoes an activated process, a membrane growth process, and a redox phase transformation process. The solid charge-transfer capability of Cu2 S is quantified with a high exchange-current density of 2.27 A/cm2, which elucidates that the Cu/Cu2 S electrode is a qualified material for counter electrodes of QDSSC. These results aid understanding of the physicochemical mechanism of QDSSC with a polysulfide electrolyte and Cu/Cu2 S counter electrode.
