A set of five novel oligo-thienylenevinylene organic molecules have been synthesized and characterized for use as electron donor moieties in bulk-heterojunction solution-processed organic solar cells combined with PC₇₁BM as an electron acceptor. The results show a broad range of solar-to-electrical conversion efficiencies, with values up to 4.9% achieved with a photocurrent value as high as 12 mA cm⁻² under standard measurement conditions. Moreover, another aim of this study was to determine the main limiting processes that control the final performance parameters of these devices. Photo-induced charge transfer measurements, such as charge extraction (CE), Transient Photo-Voltage (TPV) and mobility measurements, were carried out in order to determine the main loss mechanisms and to correlate them with the electron donor molecular design.