In this study, we aimed to develop semitransparent solar cells (STSCs) using hydrogenated amorphous silicon (a-Si:H) at a low temperature of 150 degrees C to support the fabrication of flexible solar modules, applicable in buildingintegrated photovoltaics (BIPV). To compensate for the presumable loss of device performance at such a low processing temperature, careful control of the p/i interface is proposed. We fabricated buffer layers with hydrogen (H-2)/silane (SiH4) gas flow ratios (R) ranging from 4 to 16 (R-4-R-16) to investigate their characteristics and incorporate them at the p/i interface by considering energy band matching. By employing this buffer, the power conversion efficiency (PCE) of a STSC was improved from 4.83% to 5.57% which is the best record in a-Si:H STSCs processed at a low temperature of 150 degrees C. This p/i interfacial buffer can support the realization of flexible a-Si: H-based BIPV systems using plastic-or polymer-based substrates.