Physicochemical study of discotic liquid crystal decacyclene derivative and utilization in polymer photovoltaic devices

Electrochemical and optoelectronic characteristics of discotic 1,7,13-heptanoyldecacyclene (C7DC) were studied. Introduction of carbonyl group to decacyclene resulted in a positive shift of the first reduction potential of more than 300 mV. Photoluminescence quenching was observed when combined with poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), and it was confirmed that the tri-substituted decacyclene functioned as a novel acceptor material. Spin-coated photovoltaic devices containing MEH-PPV and C7DC showed a relatively high open circuit voltage of 1.3 V, possibly because of the high lowest unoccupied molecular orbital (LUMO) position of C7DC. The photovoltaic performance of the devices was improved after annealing at 100 °C, liquid crystal transition temperature for C7DC. Morphological study revealed large crystal-like structures of C7DC in the active layer, indicating improvement of electron transport through C7DC after annealing.