Department of Chemistry; Institute of Advanced Material
Most of the currently available small molecule bulk heterojunction organic solar cells (BHJ OSCs) only utilize visible light and, to further increase the efficiency, the development of new organic materials that harvest near-infrared (NIR) light to produce an electric current is essential. Herein, a new A–π2–D–π1–D–π2–A type dimeric porphyrin-cored small molecule (CS-DP) is designed, synthesized and characterized. The use of CS-DP with a narrow bandgap (Eg) (1.22 eV) and the deep energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) affords the highest power conversion efficiency of 8.29% in BHJ OSCs with PC71BM as an acceptor, corresponding to a short circuit current of 15.19 mA cm−2, an open circuit voltage of 0.796 V and a fill factor of 70% under AM 1.5G solar irradiation. The high device performance is attributed to the visible-near-infrared light-harvesting capability of CS-DP, and the super low energy loss feature. The energy loss (Eloss) lies between 0.43 and 0.51 eV in the system, which is related to the very small energy offset of the LUMOs between the CS-DP donor and PC71BM (ΔELUMO = 0.06 eV). The value of ΔELUMO, which is considered as a driving force for the photoinduced charge separation, is much smaller than the empirical threshold of 0.3 eV, but would not be a limiting factor in the charge separation process. The results indicate that there may be room for further improving the PCE for low bandgap dimeric porphyrin systems.
Source Publication Title
Journal of Materials Chemistry A
Royal Society of Chemistry
This journal is © The Royal Society of Chemistry 2017
This work was supported by the National Natural Science Foundation of China (51473053, 91333206), Hong Kong Research Grants Council (HKBU 22304115-ECS), Areas of Excellence Scheme ([AoE/P-03/08]), Hong Kong Baptist University (FRG1/15-16/052, FRG2/16-17/024). X. Zhu thanks The Science, Technology and Innovation Committee of Shenzhen Municipality (JCYJ20150630164505504) for support. X. Z. Wang thanks the project of Innovation Platform Open Foundation of University of Hunan Province (14K092) and Hunan 2011 Collaborative Innovation Center of Chemical Engineering & Technology with Environmental Benignity and Effective Resource Utilization for the support. X. B. Peng thanks International Science & Technology Cooperation Program of China (2013DFG52740) for support. Portions of this research were carried out at beamline 7.3.3 and 18.104.22.168 at the Advanced Light Source, Lawrence Berkeley National Laboratory, which was supported by the DOE, Office of Science, and Office of Basic Energy Sciences.
Link to Publisher's Edition
Chen, S., Yan, L., Xiao, L., Gao, K., Tang, W., Wang, C., Zhu, C., Wang, X., Liu, F., Peng, X., Wong, W., & Zhu, X. (2017). A visible-near-infrared absorbing A–π2–D–π1–D–π2–A type dimeric-porphyrin donor for high-performance organic solar cells. Journal of Materials Chemistry A, 5 (48), 25460-25468. https://doi.org/10.1039/C7TA06217F
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