Thin films of the ordered vacancy compound CuIn5Se8 were deposited on glass substrates by multi-source co-evaporation method and photoconductivity measurements were done on the films at 10 to 300K. The two photo-active bands that were identified in the spectral response spectra of CuIn5Se8 thin films at all measured temperatures were attributed to photoactive transitions between acceptor VCu to donor InCu and valence band to conduction band transitions respectively. From the spectra, a shift in band-to-band gap from 1.36 to 1.3eV was observed with a temperature variation from between 10 and 300K. The non-exponential long-term decay observed in the transient photoconductivity spectra suggested a deep level trap-emptying process to be associated with the decay process and the decay constants were calculated by the differential life-time concept. From the steady state photocurrent analysis, a reduction in inter-grain potential barrier on illumination was noted as one reason for increase in conductivity on illumination. X-ray photoelectron spectroscopy analysis was done to determine the binding energies of Cu, In and Se in the compound.

Photoconductivity in the Ordered Vacancy Compound CuIn5Se8. R.R.Philip, B.Pradeep, T.Shripathi: Applied Surface Science, 2005, 250[1-4], 216-22