[16p-P6-1~32] 12.5 Organic solar cells

[16p-P6-5] Fullerene Cation-mediated Demethylation/Cyclization to 5-Membered Cyclo[60]fullerene Derivatives for Organic Solar Cells

〇Takafumi Nakagwa¹, Keisuke Ogumi², Hiroshi Okada¹, Yutaka Matsuo^1,3 (1.The Univ. of Tokyo, 2.TIRI, 3.USTC)

Keywords:fullerene derivatives, small molecular donor, open circuit voltage

Single-bonded fullerene dimers, (C₆₀R)₂ (R = (2-methoxyphenyl)dimethylsilylmethyl, (isopropoxy)dimethylsilylmethyl and 2-methoxy-5-methylphenyl) afforded fullerene derivatives cations (RC₆₀⁺) in the presence of oxidants (I₂, CuCl₂, or CuBr₂) to produce 5-membered cyclo[60]fullerene derivatives such as Si–O bond-containing cyclo[60]fullerene. The reaction mechanism includes thermally homolytic cleavage to fullerene radicals and oxidation of them to generate fullerene cations, in which the fullerene cationic centers have interaction with the oxygen atoms of methoxy groups to undergo methylative cyclization giving cyclized products. The 5-membered cyclo[60]fullerene was used in bulk-heterojunctoin organic solar cells with small molecular donor DPP(TBFu)2 (3, 6- Bis[5- (2-benzofuranyl)-2-thienyl] -2, 5-bis(2-ethylhexyl) pyrrolo [3, 4-c] pyrrole-1, 4-dione) and showed moderate power conversion efficiency (2.12%) and respectable open-circuit voltage (0.90 V) in modified conditions.