Temperature-dependent absorption edge and photoconductivity of Tl2In2S3Se layered single crystals

Abstract: Temperature variation of indirect band gap of Tl2In2S3Se layered single crystals were obtained by means of absorption and photoconductivity measurements. The temperature coefficient of −7.1×10−4 eV/K from absorption measurements in the temperature range of 10–300K in the wavelength range of 520–1100nm and −5.0×10−4 eV/K from PC measurements in the temperature range of 132–291K in the wavelength range of 443–620nm upon supplying voltage V =80V were obtained. From the analysis of dark conductivity measurements in the temperature range of 150–300K, conductivity activation energy was obtained as 0.51eV above 242K. The degree of the disorder, the density of localized states near Fermi level, the average hopping distance and average hopping energy of Tl2In2S3Se crystals were found as, 1.9×105 K, N f =4×1020 cm−3eV−1, 29.1Å and 24.2meV in the temperature range of 171–237K, respectively. Activation energy of hopping conductivity at T =171K was obtained as 41.3meV and the concentration of trapping states was found as 1.6×1019 cm−3. [Copyright &y& Elsevier]