The present study focuses on enhancing the efficiency of back-illuminated dye-sensitized solar cells (DSCs) by incorporating a SiO2 mesoporous layer on a TiO2 electrode. The performance of the DSCs is investigated by incident photon conversion efficiency (IPCE) and electrochemical impedance spectroscopy (EIS). It is observed that the photocurrent increases when the TiO2 electrode is coated with a SiO2 layer, resulting in an increase in the incident light to the dye-TiO2 electrode, especially in the wavelength range 400-600 nm. The TiO2 electrode coated with 500 nm diameter mesoporous SiO2 exhibits better device performance than that using 100 nm diameter SiO2 particles. With this modification, the Ti foil-based flexible sub-module DSC (5 cm × 10 cm) shows a high conversion efficiency of 7.13% under illumination of 100 mW cm-2 (AM 1.5), as well as good stability.