Fusing together nitrogen-rich building blocks to design new quinoxaline based non-fullerene electron acceptors for organic photovoltaics Liaqat Ali 1 , Zeeshan Abid 1 , Sughra Gulzar 1 , Ikraam Ali 2 1 Department of Chemistry, Government College University Lahore, Pakistan, 2 School of Biological and Behavioural Sciences, Queen Mary University of London, United Kingdom Clean and renewable energy production has attracted a great deal of attention in pursuit of the Sustainable Development Goal of “ensuring affordable, reliable, sustainable and modern energy for all”. 1 Organic Solar Cells (OSCs) based on electron donor and electron acceptor building blocks are amongst the most promising renewable energy conversion solutions. Combining the features of low-cost and flexibility, OSCs are idealized for portable electronic devices, indoor light-harvesting applications and building-integrated photovoltaics. In the early phases of OSCs development, the traditional fullerene-based electron acceptors suffered several challenges such as inconvenient production, restricted tunability of energy levels, high processing costs, morphological instability and low photo absorption in the visible region. 2, 3 Recent breakthroughs in material design have resolved many of these issues by imparting a greater choice of synthetic protocols and precise optimization of optical and electronic properties, 4 thereby driving power conversion efficiency (PCE) beyond 20% for single junction solar cells with bulk heterojunction architecture.5Fused-ring non-fullerene electron acceptors have frequently exhibited champion PCEs owing to a well-connected π-conjugated framework which enables higher electron charge transfer and electron mobilities.6Herein, we introduce new non-fullerene acceptors containing a benzothiadiazole fused-ring core flanked with several electron-deficient end groups. The nitrogen-rich groups impart both electron donating and electron withdrawing features into the molecules resulting in interesting balance of charges across the framework. Computational studies of the molecules reveal the possibility of band gap engineering by the introduction of halogen atoms on the periphery, thus allowing structure tuneability for optimum photovoltaic performance. Further, ongoing photophysical and electrochemical studies are used to elucidate optoelectronic properties and device performance. References 1. https://www.un.org/sustainabledevelopment/energy/.Abid, Z.; Wahad, F.; Gulzar, S.; Ashiq, M. F.; Aslam, M. S.; Shahid, M.; Altaf, M.; Ashraf, R. S., Solar Cell Efficiency Energy Materials. Fundamentals of Solar Cell Design 2021 , 271-315. 2. Nielsen, C. B.; Holliday, S.; Chen, H. Y.; Cryer, S. J.; McCulloch, I., Non-Fullerene Electron Acceptors for Use in Organic Solar Cells. Accounts of Chemical Research 2015, 48 (11), 2803-2812. 3. Karki, A.; Gillett, A. J.; Friend, R. H.; Nguyen, T. Q., The path to 20% power conversion efficiencies in nonfullerene acceptor organic solar cells. Advanced Energy Materials 2021, 11 (15), 2003441. 4. Li, C.; Zhou, J.; Song, J.; Xu, J.; Zhang, H.; Zhang, X.; Guo, J.; Zhu, L.; Wei, D.; Han, G., Non-fullerene acceptors with branched side chains and improved molecular packing to exceed 18% efficiency in organic solar cells. Nature Energy 2021, 6 (6), 605-613. 5. Holliday, S.; Ashraf, R. S.; Nielsen, C. B.; Kirkus, M.; Rö hr, J. A.; Tan, C.-H.; Collado-Fregoso, E.; Knall, A.-C.; Durrant, J. R.; Nelson, J., A rhodanine flanked nonfullerene acceptor for solution-processed organic photovoltaics. Journal of the American Chemical Society 2015, 137 (2), 898-904.
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