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

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 10–300 K in the wavelength range of 520–1100 nm and −5.0 × 10−4 eV/K from PC measurements in the temperature range of 132–291 K in the wavelength range of 443–620 nm upon supplying voltage V = 80 V were obtained. From the analysis of dark conductivity measurements in the temperature range of 150–300 K, conductivity activation energy was obtained as 0.51 eV above 242 K. 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, Nf = 4 × 1020 cm−3eV−1, 29.1 Å and 24.2 meV in the temperature range of 171–237 K, respectively. Activation energy of hopping conductivity at T = 171 K was obtained as 41.3 meV and the concentration of trapping states was found as 1.6 × 1019 cm−3.

► Transmission and photoconductivity measurements were carried out on the crystal. ► The temperature dependence of band gap energy of Tl2In2S3Se crystal was studied. ► Activation energy and Mott’s parameters of the crystal were determined. ► Obtained results indicated that the crystal has highly defective structure.