Abstract
For the purpose of developing novel photovoltaic materials, 5,5″-biformyl-2,2′:5′,2″-terthiophene (OHC-3T-CHO) and 5,5″″-biformyl-2,2′:5′,2″:5″,2″′:5″′,2″″-q-uinquethiophene (OHC-5T-CHO) were synthesized. The photovoltaic properties of OHC-3T-CHO and OHC-5T-CHO were studied. We have fabricated two flexible organic photovoltaic devices using OHC-3T-CHO, OHC-5T-CHO, and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA). The PET-ITO (indium tin oxides coated with polyethylene terephthalate)/OHC-3T-CHO/PTCDA/Al device has an open circuit voltage (V oc ) of 1.12 V, and photoelectric conversion efficiency (PCE) of 1.00%, whereas the PET-ITO/OHC-5T-CHO/PTCDA/Al device has a V oc of 1.78 V and PCE of 1.08%. Both devices have high V oc (1.12 V and 1.78 V). It is possible that intermolecular hydrogen bonding between the –CHO group of OHC-nT-CHO and the carboxylic dianhydride of PTCDA enhanced the efficiency by promoting forward interfacial electron transfer.
ACKNOWLEDGMENTS
This work was supported by the Ministry of Science and Technology of China (National Key Program for Basic Research, No. 2001-CCA03500) and the Natural Science Foundation of China NSFC (nos. 20674022, 20534020, and 20774031). We also thank the Natural Science Foundations of Guangdong (Nos. 04105931 and 2006A10702003) and Guangzhou (No. 2004J1-C0041) for financial support.