Photovoltaic molecules based on vinylene-bridged oligothiophene applied for bulk-heterojunction organic solar cells

Abstract We have synthesized two photovoltaic molecules (HEX-3TVT-ID and EH-3TVT-ID) based on vinylene-bridged oligothiophene applied as donor for the solution-processable bulk-heterojunction organic solar cells (OSCs). Vinylene unit was introduced as π -bridge in the oligothiophenes with 1,3-indenedione as end group and 4,4′-dihexyl-2,2′:5′,2′-terthiophene or 3′,4′-di(octan-3-yl)-2,2′:5′,2′-terthiophene as core, respectively. Due to the different substituent positions of the alkyl group relative to the vinylene unit in the terthiophene, HEX-3TVT-ID and EH-3TVT-ID show different optical and electrochemical properties, corresponding to the photovoltaic performance of the OSCs devices. The power conversion efficiency (PCE) of the OSCs based on a blend of HEX-3TVT-ID and PC 71 BM (1:0.8, weight ratio, 0.5% CN) reached 2.3%. In comparison, the OSCs based on the blend of EH-3TVT-ID and PC 71 BM in the weight ratio of 1:1 without the additive show a higher PCE of 2.7%, with a typically high V OC of 0.93 V, under the illumination of AM 1.5, 100 mW cm −2 .