A cover glass integrated with subwavelength structures (SWSs) and quantum dots (QDs) was realized to enhance the spectral response of Cu(In1-xGax)Se-2 (CIGS) thin film solar cells. The nanoscale SWSs was produced on the front and backside of cover glass using the self-masked etching method. The fabricated SWSs-integrated glass (SIG) exhibited superior anti-reflective properties over a broad wavelength range and a broad range of incident angle. The average transmittance of the single and double-sided SIG was increased from 92.4% to 95.2% and 97.8% in the wavelength range between 300 and 1200 nm, as compared to that of a flat surface glass. QDs were formed between the fabricated SIG and ZnO layer to act as a luminescent down-shifting (LDS) layer. A large amount of light can pass through the SIG, enhancing the efficiency of the LDS by improving light absorption and lowering reflection. After successful integration of the SIG with QDs (QD/SIG) on top of the CIGS devices, photovoltaic performance was significantly improved. The power conversion efficiency of the CIGS devices integrated with QD/double-sided SIG was improved by 7.41%, compared with that of a reference device (without QD/cover glass). The efficiency improvement is attributed to the enhanced solar energy harvesting by the efficient LDS and the minimized surface reflection loss.