Abstract
The compound Cu(In0.6Ga0.4)3Se5 prepared by fusion in sealed tube is a wide band gap semiconductor; it crystallizes in the P-chalcopyrite structure with a direct transition of 1.42 eV. Its transport properties exhibit a semi-conducting behavior, which seem to be not intrinsic but rather attributed to selenium vacancies, and the conductivity is well described by small-polaron hopping: σ = σ0exp{−29/kT}(Ohm cm)−1 with an effective mass of ∼2m 0. The thermo-power is negative and changes little with temperature, suggesting that the conduction mechanism is mostly due to electron hopping. The analyzed material shows a chemical stability over a broad pH range; the semi-logarithmic plot in KOH solution displays an exchange current density of 27 μA cm−2 and a corrosion potential of −0.204 VSCE. The capacitance measurement (C −2–V) exhibits a linear behavior, characteristic of n type conductivity, from which a flat band potential of −0.530 VSCE and an electron density of 3.49 × 1020 cm−3 are determined. The Nyquist plot shows a semicircle due to the predominance of the bulk contribution (=127 Ohm cm2) and a low density of surface states. The centre is localized below the real axis with a depression angle of 12° ascribed to a constant phase element (CPE). The straight line in the low frequencies region is due to the Warburg diffusion.
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