Title: Rationally Designed Donor–Acceptor Random Copolymers with Optimized Complementary Light Absorption for Highly Efﬁcient All-Polymer Solar Cells
Author: Sang Woo Kim, Joonhyeong Choi, Thi Thu Trang Bui, Changyeon Lee, Changsoon Cho, Kwangmin Na, Jihye Jung, Chang Eun Song, Biwu Ma, Jung-Yong Lee, Won Suk Shin,* and Bumjoon J. Kim*
Journal: Adv. Funct. Mater. 2017, 27, 1703070
Abstract: Most of the high-performance all-polymer solar cells (all-PSCs) reported to date are based on polymer donor and polymer acceptor pairs with largely overlapped light absorption properties, which seriously limits the efﬁciency of all-PSCs. This study reports the development of a series of random copolymer donors possessing complementary light absorption with the naphthalenediimide-based polymer acceptor P(NDI2HD-T2) for highly efﬁcient all-PSCs. By controlling the molar ratio of the electron-rich benzodithiophene (BDTT) and electron-deﬁcient ﬂuorinated-thienothiophene (TT-F) units, a series of polymer donors with BDTT:TT-F ratios of 1:1 (P1), 3:1 (P2), 5:1 (P3), and 7:1 (P4) are prepared. The synthetic control of polymer composition allows for precise tuning of the light absorption properties of these new polymer donors, enabling optimization of light absorption properties to complement those of the P(NDI2HD-T2) acceptor. Copolymer P1 is found to be the optimal polymer donor for the fullerene-based solar cells due to its high light absorption, whereas the highest power conversion efﬁciency of 6.81% is achieved for the all-PSCs with P3, which has the most complementary light absorption with P(NDI2HD-T2).