The effect of a two-dimensional structure on the dielectric constant and photovoltaic characteristics

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 401; p. 112756
• Main Authors: Mishima, Kenji, Sakai, Taishi, Yokota, Kazumichi, Taniguchi, Masateru, Aso, Yoshio, Ie, Yutaka, Yamashita, Koichi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2020
• Subjects: Dielectric constant; Donor materials; Efficient power conversion; Impedance; Organic solar cell; Spectroscopy measurements; Theoretical material designs; Dielectric constant; Spectroscopy measurements; Organic solar cell; Donor materials; Theoretical material designs; Impedance; Efficient power conversion
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2020.112756

[Display omitted] •We report a combined theoretical and experimental study on organic donors for solar cells with high dielectric constants.•Impedance spectroscopy measurements showed that the relative dielectric constant increased unilaterally with extending the 2D structure.•Organic solar cells based on these materials show an increase in power-conversion efficiency. Along with the recent intensive studies on improvements in organic solar cell efficiency, a new material design concept of organic semiconductors has become important for the practical realization of solar cells. Donor materials with a high dielectric constant that markedly boost the efficiency have been proposed, but theoretical material designs and/or experimental results are still scarce. In this paper, we report on a combined theoretical and experimental result of donors with high dielectric constants. Our design guidelines were to bind a conventional one-dimensional thiophene-based donor molecule in a two-dimensional (2D) manner, which would lead to extended π-conjugation and a large dielectric constant. Impedance spectroscopy measurements showed that the relative dielectric constant increased unilaterally with extending the 2D structure. Organic solar cells based on these materials in the combination of [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) show that an increase in power-conversion efficiency was observed experimentally with increasing the extension of the molecular structure. These sults imply that this is a potentially promising design strategy for the 2D extension of the molecules, and it eventually leads to a high dielectric constant and to an efficient power conversion of the organic solar cell material.