title: The effect of branched versus linear alkyl side chains on the bulk heterojunction photovoltaic performance of small molecules containing both benzodithiophene and thienopyrroledione.
abstract: To evaluate the effect of side chain characteristics on the photovoltaic performance of small molecules containing both benzodithiophene (BDT) and thienopyrroledione (TPD), we designed and synthesized two such molecules, one containing a branched 2-ethylhexyl (2EH) side chain on the BDT unit (BDTEH-TTPD) and the other containing a linear n-octyl (C8) side chain on the BDT unit (BDTO-TTP). The optical and electrochemical properties and crystalline structures of these molecules were examined. Compared to BDTO-TTPD, BDTEH-TTPD, showed stronger light absorption, longer-range ordering and shorter π-π stacking distances between backbones. As a result, the power conversion efficiency of a bulk heterojunction solar cell based on BDTEH-TTPD (2.40%) was substantially higher than that of the BDTO-TTPD device (1.12%).
authors.affiliation: POSTECH Organic Electronics Laboratory, Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea. cep@postech.ac.kr.
authors.forename: Yu Jin
authors.initials: YJ
authors.lastname: Kim
authors.forename: Kwang Hun
authors.initials: KH
authors.lastname: Park
authors.forename: Jong-jin
authors.initials: JJ
authors.lastname: Ha
authors.forename: Dae Sung
authors.initials: DS
authors.lastname: Chung
authors.forename: Yun-Hi
authors.initials: YH
authors.lastname: Kim
authors.forename: Chan Eon
authors.initials: CE
authors.lastname: Park