Macromolecular Chemistry and Physics
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
October 26, 2010
Functional Polymers: Liquid crystalline additives improve the energy conversion efficiency of polymer solar cells
S. Jeong, Y. Kwon, B.-D. Choi, G. Kwak*, Y. S. Han*
One of the most important obstacles in the commercial use of polymer solar cells is their low energy conversion efficiency. In [poly(3-hexylthiophene)]:[[6,6]-phenyl C61-butyric acid methyl ester] blend films nano-sized phase separation between the two materials proved to be the crucial feature to increase this value. Several attempts have been tried to realize this morphology. Among them, the additive technique is of high importance due to the simplicity of the phase separation on the nanoscale and the molecular structural ordering within these domains. The nematic liquid crystals 5CB and 8CB were incorporated as additives in the above mentioned polymer blend films and investigated in their application in polymer solar cells. The addition of the LC leads to an improved energy conversion efficiency of 3.72% (vs. 2.14% in the reference blend film without LC), which can be attributed to the increased absorbance, higher crystallinity of P3HT, larger domain size of PC61BM and enhanced electron/hole mobility. These results indicate that nematic liquid crystals can serve as processing additives to enhance the energy conversion efficiency of polymer solar cells without the need for post-thermal annealing of the polymer blend films.
Macromol. Chem. Phys., DOI: 10.1002/macp.201000379