For thin film silicon solar cells and modules incorporating amorphous (a-Si:H) silicon as absorber materials, light trapping, i.e. increasing the path length of incoming light, plays a decisive role for device performance. Here we demonstrate the novel diffuser superstrate for thin film solar cell. For the optical measurement, the absorption reveals that the diffuser superstrate can effectively enhance the optical path for long wavelength. For the short wavelength, the randomly textured surface provides a superior antireflective effect compared with the flat glass devices. The novel diffuser superstrate provides effective antireflection and light trapping over a broad spectral range and a wide set of incidence angles, which leads to much higher power efficiency than that of the flat film devices. Further, the electric properties, such as the external quantum efficiency and the curve of current density vary with voltage, will be investigated and presented in the full paper.