Bridgman grown CuSbS2 single crystal and its application as photodetector and potential thermoelectric material

Abstract

Crystal of copper antimony disulphide (CuSbS2) measuring 4.5 cm in length and 0.8 cm in diameter was successfully grown using the vertical Bridgman technique (VBT). The orthorhombic unit cell structure and pure CuSbS2 phase of the grown crystal was confirmed by the powder X-ray diffraction and was well supported by Raman spectra. The stoichiometry of the grown crystal was confirmed by energy dispersive X-ray analysis and field emission scanning electron microscopy revealed that crystal is grown by layer growth mechanism. The Raman spectra has shown the presence of peak at 319.32 cm−1 corresponding to Sb-S bonds whereas peaks at 445.03 cm−1 and 257.27 cm−1 corresponds to S-S and Cu-S bonds. The photoluminescence spectra taken at room temperature with 488 nm excitation wavelength displays emission in different regions of the visible spectrum. Optical absorbance spectra shows that CuSbS2 single crystal possess direct bandgap of 1.57 eV which is suitable for solar cell application. The Seebeck coefficient is positive over the entire temperature range, demonstrating the sample's p-type semiconducting nature and corroborates our Hall effect measurements. Using electrical conductivity and lattice thermal conductivity values we calculated thermoelectric figure of merit i.e., ZT whose value comes nearly 0.988 at 503 K which stands in competition with reported values of the other grown crystal. Thermogravimetric (TG) curve has shown two step decomposition at four different heating rates of 5, 10, 15 and 20 K/min which is also confirmed from DTG (differential thermogravimetric analysis) curves. At room temperature, the I-V characteristics of prepared CuSbS2 single crystal photodetector are measured for parallel to plane and perpendicular to plane configuration, with various biasing voltages at 50 mW/cm2. At room temperature, a bias voltage of 0.1 V with a light intensity of 50 mW/cm2 yields responsivity and detectivity of 30 mA/W and 32.84 × 106 Jones for ⊥ to plane, which is comparable to the reported values of other materials.