title: Approach to high open-circuit voltage in organic solar cells utilizing a structural change of the oxazolino-C70 derivative.
abstract: Reactions of 2,5-Bn2 C70 (Bn=CH2 Ph) with hydroxide and ArCN (Ar=Ph, m-ClPh) followed by quenching with I2 and BnBr afforded dibenzylated and tetrabenzylated oxazolino[70]fullerenes, respectively. The latter has a novel structural configuration, in which the addends are positioned from the polar to the transequatorial region. A key structural feature of this compound is that the oxygen atom of the oxazoline ring is bound to the equatorial belt region of C70 , giving structural change in its reduced state. This enables stabilization of the reduced state, suppressing charge recombination dynamics in organic solar cells to give a high open-circuit voltage (0.85, 0.93, and 1.11 V in devices using P3HT, PTB7, and DPP(TBFu)2 , respectively).
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 5625 Renmin Street, Changchun, Jilin 130022 (P. R. China).
authors.forename: Shu-Hui
authors.initials: SH
authors.lastname: Li
authors.forename: Zong-Jun
authors.initials: ZJ
authors.lastname: Li
authors.forename: Takafumi
authors.initials: T
authors.lastname: Nakagawa
authors.forename: James W
authors.initials: JW
authors.lastname: Ryan
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Matsuo
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
keywords: electrochemistry; fullerenes; heterocyclic compounds; open-circuit voltage enhancement; organic solar cells