Annealing Effect on Optical Properties of Thalium Sulphide (Tl2S) Thin Films

This paper investigates the effect of heat treatment on the optical properties of Thalium Sulphide (Tl2S). Interest in the binary and ternary thin films has led to increased research in photovoltaic. Tl2S thin films have a number of applications in various fields. The layers of thallium sulphides are commonly produced by the deposition method from chemical solutions. The chemical bath solution was obtained by preparing obtained by adding 20 ml of 0.5M Thiourea- (a precursor for Sulphur), 10ml of 1.0M Thallium chloride (TlCl) solution (a Thalium precursor) and 1ml of 0.5M Trisodium Citrate into 100ml beaker as a complexant. Then 40ml of distilled water was added to the solution and then gently stirred at room temperature to obtain a homogenous solution.2ml of 0.3M ammonia (NH3) was added in drops until a pH of 8.0 was reached. The bath pH of the solution was measured with Mettler Toledo AG 8603 pH meter. Finally, the substrates were immersed into the precursor and deposit for 6 hrs at about 70 oC. The substrates were removed, rinsed with distilled water and allow air-drying after the deposition. One sample was labelled as-deposited with two others annealed at temperature 300 C and 350 C respectively to study the effect of annealing on the deposited films. The results show that the presence of heat in Tl2S thin films increases its properties such as reflectance of the films in the visible range, higher absorption and energy band-gap. Conversely, increase in heat treatment brought about decrease in transmittance properties of Tl2S.