Structural, optical and photoelectrochemical properties of CuIn3Se5

The morphology, optical characterization and transport properties of dense material CuIn3Se5 have been reported. CuIn3Se5 was synthesized by the fusion technique in a sealed quartz ampoule. The ingots were polycrystalline and the phase crystallizes in a P-chalcopyrite structure. The XRD pattern confirms the formation of the ordered vacancy compound. The composition (Cu = 13.3 at%, In = 31.5 at%, Se = 55.2 at%), established by energy dispersive spectroscopy, is close to the stoichiometric formulation. A band gap of 1.19 eV has been obtained from the diffuse reflectance spectrum. CuIn3Se5 exhibits semi-conducting behavior with an activation energy of 0.52 eV. The thermal variation of the thermopower indicates that the charge carriers are electrons and the conduction occurs predominantly by small polaron hopping. The dissolution rate, determined through dissolved copper, was found to be 1.2 mu mol m(-2)/year in the KCl electrolyte. The results give deeper insights into the photoelectrochemical properties investigated for the first time on the dense material. The capacitance measurement indicates linear behavior from which a flat band potential V-fb of -0.22 V-SCE and a doping density N-D of 3.75 x 10(16) cm(-3) were determined. The energy band diagram shows the potentiality for solar energy conversion. The complex impedance pattern is circular in the low frequency region and tends to a straight line in the high frequency one, attributed to the ionic diffusion.