Synthesis and Photovoltaic Properties of Donor–Acceptor Oligothiophene Derivatives Possessing Mesogenic Properties

Abstract

For the purpose of developing novel photovoltaic materials and organic photovoltaic devices with good performance characteristics, 5-cyano-2,2′:5′,2″-terthiophene (3T-CN) and 5-cyano-2,2′:5′,2″:5″,2″′-tetrathiophene (4T-CN) were synthesized. The 3T-CN and 4T-CN were donor–acceptor oligothiophene derivatives possessing mesogenic properties. The photovoltaic properties of 3T-CN and 4T-CN were studied. The rigid and flexible photovoltaic devices were fabricated using 3T-CN, 4T-CN, and 3,4,9,10-perylenetertracarboxylic dianhydride (PTCDA). The results showed that the -CN group played an important role in increasing short circuit current density (I _sc) and power conversion efficiency (PCE). Both rigid device glass-ITO/4T-CN/PTCDA/Al and flexible device PET-ITO (indium tin oxides coated with polyethylene terephthalate)/4T-CN/PTCDA/Al had greater I _sc and PCE compared with rigid device glass-ITO/4T/PTCDA/Al. It was possible that the -CN group, with strong electron-withdrawing character, and mesogenic properties of 4T-CN enhanced the efficiency by promoting forward interfacial electron transfer.

Keywords:

• Cyano group
• mesogenic property
• oligothiophene derivative
• photovoltaic property
• rigid and flexible photovoltaic devices

ACKNOWLEDGMENTS

This work was supported by the Natural Science Foundation of China (Nos. 20674022 and 20774031). The authors also thank the Natural Science Foundation of Guangdong (Nos. 2006A10702003 and 2009B090300025) for financial support.