We report the synthesis of novel acceptor-substituted oligothiophenes and their application in m-i-p type planar heterojunction solar cells. Optical absorption spectra and electrochemical properties of the dyes are investigated. The determined energy levels of these dyes suggest that they should be ideal for use in heterojunction solar cells. We further investigate the influence of acceptor groups on the device performance by introducing 1,1-dicyano-2-methyl-vinyl and 1,1-dicyano-2-phenyl-vinyl groups, respectively, as acceptor units. Photovoltaic devices incorporating these dyes show an open circuit voltage of up to 0.96 V and power conversion efficiencies in the range of 1.5–3.0% under full sun illumination (simulated AM 1.5G sunlight, 100 mW cm−2).