Reactively Evaporated p-type Pb_3.58Sb_4.42Se₁₀ Thin Film: A Candidate for Photovoltaic and Thermoelectric Applications

Abstract

For the first time it is reported that thin films of Pb_3.58Sb_4.42Se₁₀ are prepared using reactive evaporation technique under optimized deposition conditions. As prepared films are preliminarily characterized using X-ray Diffraction, X-ray photoelectron spectroscopy , Atomic Force Microscopy  and Scanning Electron Microscope. The X-ray diffraction analysis give various structural parameters such as particle size, number of crystallites per unit area, lattice strain and dislocation density and are found to be 25 nm, 3.84×10¹⁴ m^-2, 2.267×10^-3 and 1.6×10¹⁵ lines m^-2 respectively. The AFM images indicate that the film consists of very close packed grains with grain size varying between 60 nm and 90 nm. On the basis of transmission spectra, the optical band gap is  calculated and found to be about 1.31 eV with direct allowed transition. The Urbach energy, related to the width of band tail of localized states at the band edge is determined and is found to be 0.5 eV. The slow non-exponential decay of photoconductivity with time at room temperature are the characteristics of the continuous distribution of localized states in the material. Low temperature thermoelectric power (TEP) measurements indicate the p-type conductivity for the film with Seebeck Coefficient of about 1691 μVK^-1 at room temperature.