Effect of thermal annealing on the structure, morphology, and electrical properties of Mo bottom electrodes for solar cell applications

In this paper, low-resistivity molybdenum (Mo) thin films were deposited on stainless- steel and soda-lime glass substrates with good adhesion at room temperature by using a direct current (DC) magnetron technique. The Mo thin films were annealed at different temperatures in order to enhance their structural and electrical properties so that they could be used for the solar cell applications. The Mo thin film is the bottom electrode used in the chalcopyrite solar cell family (CuInSe₂ and its alloys) because of the low resistivity of the Cu(InGa)Se₂/Mo contact. X-ray diffraction (XRD) analysis showed that these Mo films were polycrystalline in nature and exhibited better crystallization with increasing crystallite size as the annealing temperature was raised from 400 to 800 °C. The Mo film's crystallite size was observed to increase from 80 to 450 nm as the annealing temperature was increased from as-deposited to 800 °C. The microstructure, surface morphology and homogenous grains, were observed using field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM).