title: Enhancement of Open-Circuit Voltage by Using the 58-π Silylmethyl Fullerenes in Small-Molecule Organic Solar Cells.
abstract: The application of 58-π-1,4-bis(silylmethyl)[60]fullerenes, C60 (CH2 SiMe2 Ph)(CH2 SiMe2 Ar) (Ar=Ph and 2-methoxylphenyl for SIMEF-1 and SIMEF-2, respectively), in small-molecule organic solar cells with a diketopyrrolopyrrole donor (3,6-bis[5-(benzofuran-2-yl)thiophen-2-yl]-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP(TBFu)2 )) is demonstrated. With the 58-π-silylmethyl fullerene acceptor, SIMEF-1, the devices showed the highest efficiency of 4.57 % with an average of 4.10 %. They manifested an improved open-circuit voltage (1.03 V) owing to the high-lying LUMO level of SIMEF-1, while maintaining a high short-circuit density (9.91 mA cm(-2) ) through controlling the crystallinity of DPP by thermal treatment. On the other hand, despite even higher open-circuit voltage (1.05 V), SIMEF-2-based devices showed lower performances of 3.53 %, owing to a low short-circuit current density (8.33 mA cm(-2) ) and fill factor (0.40) arising from the asymmetric structure, which results in a lower mobility and immiscibility.
authors: Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
authors: Il
authors: I
authors: Jeon
authors: Department of Mechanical Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
authors: Clément
authors: C
authors: Delacou
authors: Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
authors: Takafumi
authors: T
authors: Nakagawa
authors: Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. matsuo@chem.s.u-tokyo.ac.jp.
authors: Yutaka
authors: 0000-0001-9084-9670
authors: Y
authors: Matsuo
keywords: donor-acceptor systems; electrochemistry; fullerenes; photochemistry; solar cells