Sequential coating of Sb-doped SnO2 nanowire for photoelectrochemical cells of panchromatic light absorption and low thermalization loss

Abstract

A photoelectrochemical (PEC) cell is a device of enormous potential in producing hydrogen via water splitting using solar energy. However, the low charge collection efficiency and thermalization loss of a photoelectrode limit the performance of the PEC cell. In this study, these problems are addressed by sequentially coating CdS and CdSe along the longitudinal direction of antimony-doped tin oxide and tin oxide nanowire (NW) arrays. Because of the vertical alignment of CdS and CdSe, larger band gap material (CdS) and smaller band gap material (CdSe) absorb blue and red light, respectively. Such selective absorption reduces the thermalization loss and increases the photocurrent density. In addition, antimony-doped tin oxide NWs increase the collection efficiency of photogenerated carriers and decrease the onset voltage by increasing the electric conductivity and decreasing the mismatch in the Fermi energy level. The photocurrent of the vertically aligned CdS and CdSe on antimony-doped tin oxide NWs is 17.6 mA cm−2, which is 50% higher than that of the traditional cascade-type CdSe/CdS photoelectrode.