title: Effects of alkyl chain length on the optoelectronic properties and performance of pyrrolo-perylene solar cells.
abstract: While the impact of alkyl side-chain length on the photovoltaic properties of conjugated polymers and their performance in bulk heterojunction (BHJ) solar cells has been studied extensively, analogous studies on pyrrolo-perylene-based polymers have not received adequate attention. To explore these effects, we synthesized two copolymers based on N-annulated pyrrolo-perylene and consisting of cyano group substituents on thiophene vinylene thiophene units with two different alkyl groups of 2-decyltetradecyl and 7-decylnonadecyl, and we studied them with regard to chemical structure and photovoltaic performance. UV-vis spectroscopy and cyclic voltammetry studies showed that variations in alkyl chain length affect crystallization, light absorption, and the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels. These factors have a pronounced impact on the morphology of BHJ thin films and their charge carrier separation and transportation characteristics, which, in turn, influences photovoltaic properties.
authors.affiliation: †Department of Chemistry and Research Institute of for Green Energy Convergence Technology (RIGET), Gyeongsang National University, Jinju, 660-701, Republic of Korea.
authors.forename: Xianqing
authors.initials: X
authors.lastname: Liu
authors.affiliation: ‡POSTECH Organic Electronics Laboratory, Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea.
authors.forename: Yu Jin
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: †Department of Chemistry and Research Institute of for Green Energy Convergence Technology (RIGET), Gyeongsang National University, Jinju, 660-701, Republic of Korea.
authors.forename: Yeon Hee
authors.initials: YH
authors.lastname: Ha
authors.affiliation: §Department of Polymer Science and Engineering, Huaqiao University, Quanzhou, China.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: ‡POSTECH Organic Electronics Laboratory, Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea.
authors.forename: Chan Eon
authors.initials: CE
authors.lastname: Park
authors.affiliation: †Department of Chemistry and Research Institute of for Green Energy Convergence Technology (RIGET), Gyeongsang National University, Jinju, 660-701, Republic of Korea.
authors.forename: Yun-Hi
authors.initials: YH
authors.lastname: Kim
keywords: alkyl side chain; bulk heterojunction solar cell; conjugated polymer; organic solar cell; pyrrolo-perylene unit