title: Fullerene mixing effect on carrier formation in bulk-hetero organic solar cell.
abstract: Organic solar cells (OSCs) with a bulk-heterojunction (BHJ) are promising energy conversion devices, because they are flexible and environmental-friendly, and can be fabricated by low-cost roll-to-roll process. Here, we systematically investigated the interrelations between photovoltaic properties and the domain morphology of the active layer in OSCs based on films of poly-(9,9-dioctylfluorene-co-bithiophene) (F8T2)/[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) blend annealed at various temperatures (Tan). The scanning transmission X-ray microscopy (STXM) revealed that fullerene mixing (ΦFullerene) in the polymer matrix decreases with increase in Tan while the domain size (L) is nearly independent of Tan. The TEM-S mapping image suggests that the polymer matrix consist of polymer clusters of several nm and fullerene. We found that the charge formation efficiency (ΦCF), internal quantum efficiency (ΦIQ), and power conversion efficiency (PCE) are dominantly determined by ΦFullerene. We interpreted these observations in terms of the polymer clusters within the polymer matrix.
authors.affiliation: 1] Faculty of Pure and Applied Science, Univ. of Tsukuba, Tsukuba 305-8571, Japan [2] Center for Integrated Research in Fundamental Science and Engineering (CiRfSE), Univ. of Tsukuba, Tsukuba 305-8571, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Moritomo
authors.affiliation: Photovoltaic Materials Unit, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Faculty of Pure and Applied Science, Univ. of Tsukuba, Tsukuba 305-8571, Japan.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Yonezawa
authors.affiliation: 1] Faculty of Pure and Applied Science, Univ. of Tsukuba, Tsukuba 305-8571, Japan [2] PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan.
authors.forename: Takeaki
authors.initials: T
authors.lastname: Sakurai
authors.affiliation: Institute of Materials Structure Science, High-Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Takeichi
authors.affiliation: Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-hiroshima, Hiroshima 739-8526, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Suga
authors.affiliation: 1] Institute of Materials Structure Science, High-Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan [2] Department of Earth and Planetary Science, Univ. of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Institute of Materials Structure Science, High-Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Inami
authors.affiliation: Institute of Materials Structure Science, High-Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Mase
authors.affiliation: Institute of Materials Structure Science, High-Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Kanta
authors.initials: K
authors.lastname: Ono
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