EFFECT OF SUBSTRATE TEMPERATURE ON THE STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF NEBULISED SPRAY PYROLYSED Bi2S3 THIN FILMS

Identification of potential materials for photoelectrochemical solar energy conversion has always been a challenging task. The prospective materials should possess a suitable band gap (1.41.7eV), high absorption coefficient, low resistivity and should be non-toxic and available at low cost. Metal chalcogenides are suitable materials for photovoltaic applications. In particular bismuth trisulphide (Bi2S3) which belong to V-VI group of semiconductors is a potential material for photoelectrochemical solar energy application. Bi2S3 possess an optical band gap of 1.7 eV, absorption coefficient of the order of 10 5 and is non-toxic. Bi2S3 thin films are deposited by a number of techniques such as chemical bath deposition[1], SILAR[2], electrodeposition[3], vacuum evaporation[4] and spray pyrolysis [5]. It was found that the properties of Bi2S3 thin film varies with the method of deposition, deposition parameters and post deposition treatments. It is essential to deposit Bi2S3 thin films by an appropriate technique and to optimize the deposition parameters to obtain thin films with reproducible properties. In the previous work authors have reported a deposition and characteristics of Bi2S3 thin film by a novel method known as nebulised spray pyrolysis. The properties of spray pyrolysed films depend on spray parameters such as substrate temperature, substrate-nozzle distance, precursor concentration, geometry of the spray gun, size and shape of the droplets. Substrate temperature is the important parameter that influences the characteristics of the films the most. It is essential to optimise the temperature of the substrate to deposit device quality thin film. And hence in the present work an attempt has been to study the effect of substrate temperature on the structural, optical and electrical properties of the