Tuning the properties of RF sputtered tin sulphide thin films and enhanced performance in RF sputtered SnS thin films hetero-junction solar cell devices

Abstract

Abstract Tin sulphide (SnS) thin films were grown using the RF sputtering techniques. The working pressures (WP) were tuned between 0.70 and 4.00 Pa at fixed RF power of 100 W and deposition time of 2 min. X-ray diffractometry studies indicate that the films crystallized in the orthorhombic crystal structure and were single phase. The crystallite size increased up to a critical working pressure of 1.33 Pa and decreased thereafter with increased WP. Scanning electron microscopy (SEM) indicates that the films exhibit columnar grain structures. Energy dispersive spectroscopy indicates that the films are slightly Sn-rich. Transmittance and reflectance plots exhibits interference pattern, an indication that the films were of uniform thickness. Analysis from the optical data gives optical absorption coefficient (α) > 104 cm−1, and direct energy bandgap that exhibits relative decrease with the deposition conditions. Electrical studies from Hall effect measurements indicates that the films possess p-type electrical conductivity, and carrier concentration of 1016 cm−3 for films grown at WP of 1.33 Pa. The RF sputtered SnS thin films grown on Mo-substrates served as absorber layers to fabricate thin film hetero-junction solar cell devices in the substrate configuration with a cadmium sulphide (CdS) window partner. The best device yielded a short circuit current density of 25.94 mA/cm2, open circuit voltage of 0.087 V and an enhanced solar conversion efficiency of 0.60%. A world record value for RF-sputtered SnS/CdS based hetero-junction thin film solar cell devices.