Highly photosensitive and wide bandgap amorphous silicon oxide (a-SiO_x:H) films were developed at low temperature ranges (100~150℃) with employing plasma-enhanced chemical vapor deposition by optimizing H₂/SiH₄ gas ratio and CO₂ flow. Photosensitivity more than 10⁵ and wide bandgap (1.81~1.85 eV) properties were used for making the a-SiO_x:H thin film solar cells, which exhibited a high open circuit voltage of 0.987 V at the substrate temperature of 100℃. In addition, a power conversion efficiency of 6.87% for the cell could be improved up to 7.77% by employing a new n-type nc-SiO_x:H/ZnO:Al/Ag triple back-reflector that offers better short circuit currents in the thin film photovoltaic devices.