Benzothiadiazole-sandwiched quarter thiophene-based oligomer for organic solar cells

A novel diphenylaminofluorenyl-capped benzothiadiazole-sandwiched quarter thiophene-based narrow band-gap oligomer 4,7-bis-{[5-(9,9-bis(octyl)-7-diphenylaminofluorene-2-yl)-thiophen-2-yl]-5-thiophen-2-yl}-[2,1,3] benzothiadiazole (DPAFL–DBBT–DPAFL which is further abbreviated to DDBBTD) has been synthesized and characterized. The obtained molecule absorbs light from 300 to 800 nm in solid film. PL peak of DDBBTD in solid film is centered at 731 nm. Photovoltaic cell by using the blend of the obtained oligomer and PCBM as active layer was fabricated by spin-coating method. Open-circuit voltage reached 0.85 V with the maximum energy conversion efficiency 0.15% and photocurrent response was extended over 700 nm.