Properties of spray deposited nano needle structured Cu-doped Sn2S3 thin films towards photovoltaic applications

Nano needle structured Cu-doped Sn2S3 thin films with different Cu concentrations (0, 1, 2 and 3 wt.%) were prepared by spray pyrolysis technique on glass substrates maintained at 400 °C. XRD analysis showed that the undoped and doped Sn2S3 films exhibit orthorhombic crystal structure with a preferential orientation along the (2 1 1) plane. SEM images confirm the presence of nano needles in both the undoped and doped films. Optical band gap is red shifted from 1.96 eV to 1.86 eV with increase in Cu concentration in the films which may be attributed to Moss-Burstein effect. All the films have resistivity in the order of 10−1 Ω-cm and the Sn2S3 film coated with 2 wt.% Cu concentration exhibit a minimum resistivity of 0.335 × 10−1 Ω cm. The obtained results infer that Sn2S3 film coated with 2 wt.% Cu concentration exhibit better physical properties.