Improved high-efficiency organic solar cells via incorporation of a conjugated polyelectrolyte interlayer.

Jung Hwa Seo, Andrea Gutacker, Yanming Sun, Hongbin Wu, Fei Huang, Yong Cao, Ullrich Scherf, Alan J Heeger, Guillermo C Bazan

Index: J. Am. Chem. Soc. 133 , 8416–8419, (2011)

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Abstract

The power conversion efficiencies of bulk heterojunction (BHJ) solar cells can be increased from 5 to 6.5% by incorporating an ultrathin conjugated polyelectrolyte (CPE) layer between the active layer and the metal cathode. Poly[N-9''-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C(71) butyric acid methyl ester (PC(71)BM) were chosen for the photoactive layer. CPEs with cationic polythiophenes, in both homopolymer and block copolymer configurations, were used to improve the electronic characteristics. The significant improvement in device performance and the simplicity of fabrication by solution processing suggest a promising and practical pathway for improving polymer solar cells with high efficiencies.