Energy and environment problems severely restrict the sustainable development of society and economy, and are two critical challenges at the present time. The utilization of solar energy is one of the best solutions to these problems, and solar cell which converts light to electricity through photovoltaic effect is an ideal device to use solar energy. Compared with traditional silicon-based solar cells, organic and inorganic/organic hybrid solar cells possess some merits, such as low cost, light weight, flexibility and semi-transparency, and have attracted much attention in recent years.
Xiaowei Zhan group in the Department of Materials Science and Engineering, College of Engineering, focuses their research on the development of high-performance materials and devices for organic and hybrid photovoltaics. Recently, Zhan group published an invited review entitled “Oligomer Molecules for Efficient Organic Photovoltaics” in Accounts of Chemical Research (Acc. Chem. Res., 2016, 49, 175−183). Oligomer molecules (OMs) are monodisperse big molecules with intermediate molecular weights (1000-10000). OMs not only overcome shortcomings of both vapor-deposited small molecules and solution-processed polymers, but also combine their advantages, such as defined molecular structure, definite molecular weight, easy purification, mass-scale production, good batch-to-batch reproducibility, good solution processability, and film-forming properties. This review summarized the recent research progress in solution-processable OM electron donors and acceptors, discussed structure-property relationships of the OMs, and addressed the remaining challenges and the key research directions in the near future.
The cover art of Accounts of Chemical Research
Zhan group also published an invited review entitled “Triarylamine: Versatile Platform for Organic, Dye-Sensitized, and Perovskite Solar Cells” in Chemical Reviews (Chem. Rev., 2016, 116, 14675−14725), in which the recent advances of the high-performance triarylamine-based materials in organic, dye-sensitized, and perovskite solar cells are systematically reviewed. The solutions to the challenges in the field of organic and hybrid photovoltaics, some design strategies for improving the materials and device performance, and possible research directions in the near future are also proposed.
During the past years, Zhan group has achieved a series of progress in the development of new materials for high-performance organic photovotaics, which have been recognized by the community of organic photovotaics. In 2015, Zhan group firstly proposed the concept of fused-ring electron acceptor (FREA, Adv. Energy Mater., 2015, 5, 1501063). These FREAs showed superior performance to traditional fullerene acceptor PC61BM (Adv. Mater., 2015, 27, 1170–1174, Energy Environ. Sci., 2015, 8, 610-616, Energy Environ. Sci., 2015, 8, 3215–3221). By optimizing the molecular and device structure, they improved the power conversion efficiency of the device to ca. 10% (J. Am. Chem. Soc., 2016, 138, 2973–2976, J. Am. Chem. Soc., 2016, 138, 4955–4961, Adv. Energy Mater., 2016, 6, 1600854). By precisely adjusting the absorption, energy levels and morphology of donor and acceptor, the efficiency of the device was further enhanced to 11% (Adv. Mater., 2016, DOI: 10.1002/adma.201604155). Besides organic solar cells, FREAs can also be applied in perovskite solar cells, and an efficiency of 19.4% was obtained (Adv. Mater., 2016, DOI: 10.1002/adma.201604545, collaborated with Prof. Jinsong Huang at University of Nebraska-Lincoln, USA). At present, FREAs designed by Zhan group are commercial available. Dozens of well-known research groups across the world have fabricated high-efficiency (>11%) devices using these FREAs, which showed better efficiency and stability than fullerene-based devices.
This work was supported by the 973 project of Ministry of Science and Technology of China and National Nature Science Foundation of China.