Drastic change of molecular orientation in a thiazolothiazole copolymer by molecular-weight control and blending with PC61BM leads to high efficiencies in solar cells.
A thiazolothiazole-thiophene copolymer is examined as the active material in bulk heterojunction (BHJ) solar cells. By optimizing the molecular weight, the polymer-based cells exhibit power conversion efficiencies as high as 5.7%. The increase in molecular weight improves the orientational order, and blending with phenyl-C61-butyric acid methyl ester (PC61BM) changes the orientational motif from edge-on to face-on, which accounts for the trend in photovoltaic performances. These results might give new insight into the structure-property relationships in BHJ solar cells.
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan; Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Chiyoda-ku 102-0075, Japan. iosaka@hiroshima-u.ac.jp.
Itaru
I
Osaka
Masahiko
M
Saito
Hiroki
H
Mori
Tomoyuki
T
Koganezawa
Kazuo
K
Takimiya
D011211:Electric Power Supplies; D037741:Fullerenes / Q000737:chemistry*; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry*; D012993:Solar Energy; D013844:Thiazoles / Q000737:chemistry*
C539575:(6,6)-phenyl C61-butyric acid methyl ester; D037741:Fullerenes; D011108:Polymers; D013844:Thiazoles