A Near-infrared Non-fullerene Electron Acceptor for High Performance Polymer Solar Cells
Yongxi Li,1 Lian Zhong,2,3 Bhoj Gautam,4 Hai-Jun Bin,2 Jiu-Dong Lin,1 Fu-PengWu,1 Zhanjun Zhang,3 Zuo-Quan Jiang,1* Zhi-Guo Zhang,2* Kenan Gundogdu, 4* Yongfang Li,2,3,5 Liang-Sheng Liao1*
1Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou 215123, China
2Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
3University of Chinese Academy of Sciences, Beijing 100049, China.
4Department of Physics and Organic and Carbon Electronics Laboratory, North Carolina State University, Raleigh, North Carolina 27695, USA
5Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
Low-bandgap polymers/molecules are an interesting family of semiconductor materials, and have enabled many recent exciting breakthroughs in the field of organic electronics, especially for organic photovoltaics (OPVs). Here, such a low-bandgap (1.43 eV) non-fullerene electron acceptor (BT-IC) bearing a fused 7-heterocyclic ring with absorption edge extending to the near-infrared (NIR) region was specially designed and synthesized. Benefitted from its NIR light harvesting, high performance OPVs were fabricated with medium bandgap polymers (J61 and J71) as donor, showing power conversion efficiency of 9.6% with J61 and 10.5% with J71 along with extremely low energy loss (0.56 eV for J61 and 0.53 eV for J71). Interestingly, femtosecond transient absorption spectroscopy studies on both two systems show that efficient charge generation were observed despite the fact that the highest occupied molecular orbital (HOMO)-HOMO offset (ΔEH) in the blends were as low as 0.10 eV, suggesting such a small ΔEH is not a crucial limitation in realizing high performance of NIR non-fullerene based OPVs. Our results indicated that BT-IC is an interesting NIR non-fullerene acceptor with great potential application in tandem/multi-junction, semitransparent, and ternary blend solar cells.