Organic solar cells (OSCs) have received considerable attention as clean energy conversion devices because of their lightweightness, cost effectiveness, flexibility, and suitability for roll-to-roll printing. In dye-sensitized solar cells the core structure has included a dye-anchored TiO
2 electrode for photoinduced charge separation, while in bulk heterojunction OSCs, the active layer of OSC devices has usually consisted of a mixture of conjugated polymers as donors and fullerene derivatives as acceptors.
1,2 In particular, the power conversion efficiency (PCE) of OSCs based on fullerene derivative acceptors has reached over 10%. However, it is difficult to further increase the PCE of fullerene-based OSCs due to their inherent limitations including arduous energy-level tunability and low absorption profile. To enhance the photovoltaic performance of OSCs, nonfullerene acceptors (NFAs) with aromatic fused-ring structures have emerged rapidly in recent years to fabricate high-efficiency OPVs. Compared to traditional fullerene acceptors, NFAs possess several advantages, such as facile synthesis and high absorption profile. Most high-performance NFAs possess acceptor-donor-acceptor (A-D-A) type structures, in which fused multi-ring ladder structures are used as the D unit and 1,1-dicyanomethylene-3-indanone (IC) derivatives as the A unit.
In this talk I will give an overview of our recent studies on rational design and synthesis of novel dyes and nonfullerene acceptors. In paticular, several nonfullerene acceptors possessing different D units have been designed and synthesized to address the relationship between the structure and the photophysical and photovoltaic properties of the A-D-A type nonfullerene acceptors.3-6
[1] T. Umeyama and H. Imahori, J. Mater. Chem. A (Feature Article), 2, 11545-11560 (2014).
[2] T. Umeyama and H. Imahori, Acc. Chem. Res. 52, 2046-2055 (2019).
[3] T. Umeyama, K. Igarashi, D. Sasada, Y. Tamai, K. Ishida, T. Koganezawa, S. Ohtani, K. Tanaka, H. Ohkita, and H. Imahori, Chem. Sci., 11, 3250-3257 (2020).
[4] T. Umeyama, K. Igarashi, D. Sasada, K. Ishida, T. Koganezawa, S. Ohtani, K. Tanaka, and H. Imahori, ACS Appl. Mater. Interfaces, 12, 39236-39244 (2020).
[5] T. Umeyama, K. Igarashi, Y. Tamai, T. Wada, T. Takeyama, D. Sasada, K. Ishida, T. Koganezawa, S. Ohtani, K. Tanaka, H. Ohkita, and H. Imahori, Sus. Energy Fuels, 5, 2028-2035 (2021).
[6] T. Umeyama, T. Wada, K. Igarashi, K. Kato, A. Yamakata, T. Takeyama, Y. Sakamoto, Y. Tamai, H. Ohkita, K. Ishida, T. Koganezawa, S. Ohtani, K. Tanaka, and H. Imahori, ACS Adv. Energy Mater., in press.
