Oil-producing microalgae are attracting attention as a biofuel other than grain. One of the challenges in producing biomass fuels from microalgae is the low Energy Profit Ratio (EPR), the ratio of energy obtained to energy input in the cultivation process. In this study, we focus on the light transmittance and design of organic photovoltaic cells (OPVs) and aim to improve the EPR by using blue OPVs that allow the light necessary for microalgae photosynthesis to both culture and generate electricity.