[17p-G202-1~21] 12.5 Organic solar cells

▼ [17p-G202-8] Effects of End-on Orientation of Polymer Chains at Donor/Acceptor Interface on Organic Photovoltaic Performance

〇(D)Fanji Wang^1,2, Kyohei Nakano², Hiroyuki Yoshida³, Tajima Keisuke² (1.Tokyo Univ., 2.RIKEN CEMS, 3.Chiba Univ.)

Keywords:organic photovoltaics, molecular orientation

Relative alignments between electron donor and acceptor molecules in thin films have a large impact on the charge separation process of organic solar cells (OSCs). In this study, the effects of the polymer chain orientations at the donor/acceptor (D/A) interface were investigated in OSCs with planer heterojunction (PHJ) structure. Poly(3-alkylthiophene)s films with edge-on (i.e. main chain aligned parallel to the D/A interface) and end-on orientation (i.e. vertical to the D/A interface) at the interface are used to construct PHJs in the combination with a fullerene derivative. The energy structures with different molecular orientations were investigated by ultraviolet photoelectron spectroscopy (UPS) and low-energy inversed photoelectron spectroscopy (LEIPS). We found that the end-on device showed improved charge separation and suppressed charge recombination compared to the edge-on device. These may be attributed to the vertical orientation of the main chain that affects the interfacial charge transfer state through the charge delocalization direction. These results provide the basic information on the relative arrangements of the molecules and the performance in OSCs.