3. CONCLUSION
In summary, we have successfully designed and synthesized three novel NFREAs OC4-4Cl-Ph , OC4-4Cl-Th andOC4-4Cl-C8 with hexylbenzene, hexylthiophene and octyl side chains at the π-bridge units. According to our results, the LUMO energy levels decrease from OC4-4Cl-Ph toOC4-4Cl-Th and OC4-4Cl-C8 . Notably, the OC4-4Cl-C8 exhibits a longer exciton diffusion distance and the corresponding blend film (D18:OC4-4Cl-C8 ) displays faster hole transfer and diffusion-mediated processes, weaker bimolecular recombination, and more efficient exciton transport. Furthermore, the D18:OC4-4Cl-C8 blend films form favourable nano fibril-like interpenetrating networks, which could facilitate exciton dissociation and charge transport. Ultimately, theOC4-4Cl-C8 devices can achieve the highest PCE of 16.56% with a low E loss of 0.56 eV, which is much higher thanOC4-4Cl-Ph (12.29%) to OC4-4Cl-Th (11.00%) based ones. To the extent that we know, 16.56% is the highest PCEs of NFREA based devices up to now. Our work demonstrates that side-chain engineering is an efficient way to fabricate high-performance NFREAs.
Acknowledgements
Financial support from the National Natural Science Foundation of China (52173174, 51933001, 22109080), the Natural Science Foundation of Shandong Province (no. ZR2022YQ45), the Taishan Scholars Program (no. tstp20221121 and no. tsqnz20221134). A portion of this work is based on the data (GISAXS) obtained at BSRF-1W1A. The authors gratefully acknowledge the cooperation of the beamline scientists at BSRF-1W1A beamline.
Xinming Zheng and Wenlong Liu contributed equally to this work.