WS: A New Window Layer Material for Solar Cell Application

Radio frequency (RF) magnetron sputtering was used to deposit tungsten disulfide (WS) thin films on top of soda lime glass substrates. The deposition power of RF magnetron sputtering varied at 50, 100, 150, 200, and 250 W to investigate the impact on film characteristics and determine the optimized conditions for suitable application in thin-film solar cells. Morphological, structural, and opto-electronic properties of as-grown films were investigated and analyzed for different deposition powers. All the WS films exhibited granular morphology and consisted of a rhombohedral phase with a strong preferential orientation toward the (101) crystal plane. Polycrystalline ultra-thin WS films with bandgap of 2.2 eV, carrier concentration of 1.01 × 10 cm, and resistivity of 0.135 Ω-cm were successfully achieved at RF deposition power of 200 W. The optimized WS thin film was successfully incorporated as a window layer for the first time in CdTe/WS solar cell. Initial investigations revealed that the newly incorporated WS window layer in CdTe solar cell demonstrated photovoltaic conversion efficiency of 1.2% with V of 379 mV, J of 11.5 mA/cm, and FF of 27.1%. This study paves the way for WS thin film as a potential window layer to be used in thin-film solar cells.