Effects of additional p-bridges on a terpolymer based on the second acceptor unit of DTBT and the performance of organic solar cells

作者：Jing, Xin; Zhao, Yong; Wang, Quanliang; Kang, Xiao; Zhuang, Tao; Liu, Xiaojie; Wang, Xiangkun; Yu, Liangmin; Sun, Mingliang^*

来源：Polymer, 2022, 254: 125089.

DOI：10.1016/j.polymer.2022.125089

• DTBT second Acceptor unit
• ?-bridges
• Organic solar cells

Fused electron acceptor units play a significant role in donor materials for organic solar cells (OSCs). This paper introduces the fused dithieno[3',2':3,4;2',3 ":5,6]benzo[1,2-c][1,2,5]thiadiazole (DTBT) units into the benzo [1,2-b:4,5-b']dithiophene-benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDT-BDD) backbones to synthesize ter polymers. The photovoltaic performance of the terpolymers is investigated by adding the pi-bridges on both sides of the DTBT. For Y6-based OSCs, the devices based on DTBT terpolymers without additional pi-bridges can obtain high open-circuit voltage (VOC) but low fill factor (FF). On the contrary, DTBT terpolymers with 3-octylthiophene pi-bridges significantly enhance the FF but decrease the VOC in devices. By investigating terpolymers' photovoltaic and quantum chemistry properties, we find that the presence of pi-bridge structures on both sides of the DTBT unit can effectively promote carrier collection and reduce the bimolecular recombination in the devices. However, its reduced charge-transfer state energy level results in high voltage losses. Therefore, the design of DTBT terpolymers for how to balance the voltage loss due to pi-bridges brought to the optimization of polymer conformation and charge excitation and conversion will become an important subject.

• 单位
  中国海洋大学