Enhancing the Performance of a Fused-Ring Electron Acceptor by Unidirectional Extension
2019
Jia, Boyu | Wang, Jing | Wu, Yao | Zhang, Mingyu | Jiang, Yufeng | Tang, Zheng | Russell, Thomas P. | Zhan, Xiaowei
The unidirectional extension of a smaller fused-ring system into a larger one in a single direction will increase the conjugation length, allowing a fine-tuning of electronic properties. Here, we designed and synthesized a unidirectionally extended fused-8-ring-based nonfullerene acceptor, AOIC, and a bidirectionally extended fused-11-ring electron acceptor, IUIC2, and compared these with the parent fused-5-ring electron acceptor, F5IC. They share the same electron-accepting groups and alkylphenyl side chains but have different fused-ring electron-donating units. Core extension from 5 to 11 rings up-shifts the energy levels, red shifts the absorption spectra, and reduces bandgaps. The unidirectionally extended AOIC has the highest mobility (2.1 × 10–³ cm² V–¹ s–¹) relative to the parent F5IC (1.0 × 10–³ cm² V–¹ s–¹) and the bidirectionally extended IUIC2 (4.7 × 10–⁴ cm² V–¹ s–¹). Upon blending with the donor PTB7-Th, AOIC-based organic photovoltaic cells show an efficiency of 13.7%, much better than that of F5IC-based cells (5.61%) and IUIC2-based cells (4.48%).
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