Photovoltaics are expected to be among next-generation energy technologies, together with wind power, biomass, and geothermal power. This chapter provides an overview of the recent development of organic solar cells in terms of synthesis chemistry and versatile synthesis methods of organic materials for solar cells and organic field-effect transistors. Ruthenium Ru(II) complexes show good photovoltaic properties: a wide light-harvesting region, suitable energy levels of excited and ground states, and relatively good stability. Organic dyes are attractive as novel sensitizers, with the following advantages compared to the expensive Ru complexes: structures with an easy design that are easy to modify, low cost and environmental burden, and a large molar extinction coefficient. An Organic Photovoltaics is a solid-type solar cell based on the semiconducting properties of organic materials, which is composed of active layers of organic semiconducting materials, buffer layers, and electrodes.