Thin film silicon is an attractive and versatile material for photovoltaics whose manufacturing reached a high level of maturity. Owing to its moderate efficiency compared to crystalline technologies, it should target either power plants with low installation cost or applications with added value like building-integration. Since the technology relies on very thin films of a weakly absorbing material, light-management is, and always has been, a key aspect of the technology. In this review, we briefly describe the class of materials that is summed up under the name "thin film silicon", point out requirements on device design, and discuss functionalities that enhance the absorption in the silicon films, addressing both their theoretical understanding as well as experimental realization.