Rationally regulating the π-bridge of small molecule acceptors for efficient organic solar cells

作者：Wang, Pengchao; Li, Yonghai^*; Han, Chenyu; Wang, Junjie; Bi, Fuzhen; Zheng, Nan^*; Yang, Jiawang; Wang, Jiuxing; Bao, Xichang^*

来源：Journal of Materials Chemistry A, 2022, 10(34): 17808-17816.

DOI：10.1039/d2ta05157e

• PERFORMANCE

Nonfullerene acceptors have boosted the power conversion efficiencies (PCE) of organic solar cells (OSCs). Rigid fused-ring molecular skeletons enable decent molecular planarity and stacking orientations, but suffer from tedious synthesis procedures for those with large pi-backbones. Promisingly, the pi-bridge strategy provides an alternative to readily manipulate the light utilization, but sometimes increases the conformation complexity. To rationally regulate the performance of pi-bridged acceptors, herein, we report two new acceptors WA1 and WA2, functionalized with single or dual pi-bridges flanking the phenylalkyl modified indacenodithiophene (IDT) backbone. The unilateral pi-bridge endows WA1 with an asymmetric electron cloud distribution, affording a greater dipole moment and well-organized molecular orientation. In contrast, the bilateral pi-bridges endow WA2 with two disparate molecular dipoles and disordered stacking orientations, generating inferior PCEs below 10%. Notably, the PM6:WA1 device shows a remarkable PCE of up to 15.45% with an impressive fill factor (FF) of up to 79.31%, both of which rank among the highest values of OSCs with pi-bridged acceptors. More importantly, the PM6:Y6:WA1 ternary organic solar cell (TOSC) affords a high PCE of up to 18.15%, which is the best efficiency among Y6-based bulk-heterojunction TOSCs and the first example of an efficient ternary cell featuring a pi-bridged guest acceptor.

• 单位
  中国科学院; 中国科学院青岛生物能源与过程研究所; 青岛大学