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Photoconductivity in the ordered vacancy compound CuIn7Se12

Rachel Reena Philip, B.Pradeep, S.Dhanya

Photoconductivity measurements are done in the temperature range 10K to 300K on thin films of the off-tie line ordered vacancy compound CuIn7Se12 which incorporates a single pair of the defect complex (2VCu-+InCu++) and two neutral Cu vacancies in every 6 units of CuInSe2. The rapid increase in photoconductivity on illumination and the rapid decay of conductivity on removal of illumination in the transient photoconductivity curves are explained as a consequence of the reduction in inter grain potential barrier on illumination and its restoration on removal of illumination. The nonexponential long- term decay observed is suggestive of a deep level trapemptying process associated with the decay process. The temperature dependence of photosensitivity and the decay constants of the material are investigated. Analysis of dark conductivity and steady state photoconductivitymeasurements yielding the variation of barrier height from0.09 eV to 0.0024 eV is found to corroborate the inferences from transient photoconductivity. Photoluminescence and spectral responsemeasurements are done to obtain information regarding the defects present in the samples.