Solar cell designing and fabrication has always fascinated researchers, physicists, scientist and engineers of photovoltaic industry. Scientist seek solution to mend the efficiency and design of thin film solar cells. This paper illustrate the comprehensive overview of thin film solar cells and their structure. Furthermore various categories of thin film solar cells, strength and weakness of solar cells and techniques to enhance the efficiency of solar cells are also discussed in this paper. Thin film solar cell technology belongs to second generation of solar cells and fabricated by depositing layers of thin film of photovoltaic material on a substrate. Most prosaic substrate used to fabricate thin film solar cells are metal, plastic and glass. Thin film solar cells are much compendious as compared to their rival crystalline solar cell technology. The size of thin film solar cell diverges from few nanometer to ten micrometers.  Review suggest that III-V semiconductor such as Gallium Nitride and Gallium Arsenide are endowed with many attractive properties for fabrication of thin film solar cell. Heterojunction thin film solar cells hold much higher efficiency compared to homojunction thin film solar cells owing to their high optical raptness.