The impedance spectroscopy of photoabsorber films prepared by high vacuum evaporation technique

Thin films of CuIn3Se5 photoabsorber were deposited from the stoichiometric polycrystalline precursor onto glass/ITO substrates by using the high vacuum evaporation technique and following annealing in argon. The chalcopyrite structure of obtained films of CuIn3Se5 were confirmed by the XRD spectroscopy. The SEM micrographs, Raman spectra and EDS data confirm the enhanced morphology and composition of prepared CuIn3Se5 films. The obtained glass/ITO/CuIn3Se5/graphite sandwich structures demonstrate diode-shape I-V characteristics and photosensitivity. The annealed CuIn3Se5 films have a p-type of conductivity with the free carriers’ concentration in the range of 1016–1017 cm−3. An electrical equivalent circuit consisting of constant phase elements was used for modeling of the impedance spectroscopy measurements. Both impedance modeling and capacitance-voltage (C−V) curves show that there is a strong minority carrier accumulation process taking place at forward potentials.