Effect of copper concentration on CTS thin films for solar cell absorber layer and photocatalysis applications

Abstract

Abstract Earth abundant, nontoxic Cu2SnS3 (CTS) thin films are prepared using low-cost ultrasonic spray pyrolysis (USP) technique by varying different copper (Cu) precursor (copper chloride) concentration. Influence of Cu concentration on the electrical, optical and structural properties of CTS thin films are studied. XRD, TEM results confirm the formation of tetragonal structure of CTS films with orientation along (112) plane. Raman analysis reconfirms the tetragonal structure of CTS thin film and Cu2S secondary phase in films with higher Cu concentration samples. Stoichiometric film is found for 0.025M Cu concentration. XPS and PL studies are also performed. The absorption coefficient of CTS films is found to be ~105 cm−1 and optical bandgap is varying from 1.32 eV to 1.49 eV. P-type semiconductor nature of the film is found from electrical characteristics with carrier concentration of ~1021/cm3. The resistivity of the film decreases from 4.6 × 10−1 to 9.5 × 10−4 Ω-cm as Cu concentration increases. These properties are suitable for solar cell absorber layer. The optimized CTS thin film is used as a photocatalyst and photocatalysis activity of methylene blue (MB) dye is examined under visible light irradiation. A significant photodegradation (~90%) of MB achieved under 3 h visible light irradiation.