Spectral distribution of photoelectrical current and free carrier life time of Tex(Sb10Se90)100−x thin films

The present work studies the effect of Te additions to Sb10Se90 films on the measurements of steady state “DC” and transient “AC” photoconductivity. The steady state photoconductivity was measured in temperature range 300–400 K. The spectral distribution of photocurrent was measured in the wavelength range 400–900 nm at different level of illumination and applied electric filed. The dependence of photocurrent (Iph) on light intensity (G) follows the power low (IphGγ) where the exponent γ determines the nature of the recombination process. Double beam spectrophotometer was used to measuring the film transmittance T (λ) nm at normal incidence of Tex(Sb10Se90)100−x (with x = 0%, 5%, 10% and 15%) films in the wavelength range 400–2500 nm. Based on the envelope method, the film thickness and the complex index of refraction were determined with accuracy better than 1%. Ac photoconductivity measurements revealed that, the carrier lifetime decrease with increasing relative light intensity and the applied electric filed. It was found that, the replacement of Sb and Se by Te atoms leads to the decrease in the activation energy for electrical conduction in the dark ΔEdc and the optical band gap Egoptor Egph, while the refractive index and the width of localized states were found to be increases.

► Effect of Te additions on optical and photoconductivity for Tex(Sb10Se90)100−x films.
► Conduction mechanism in films is due to an activated process with single activation energy.
► Photoconductivity measurements are in good agreement with optical measurement.
► Optical band gap and free carrier life time decreases with increasing Te content.