Resolving atomic-scale interactions in non-fullerene acceptor organic solar cells by high-field NMR crystallography

Benjamin Luginbuhl^a, Parth Raval^b, Tomasz Pawlak^c, Zhifang Du^a, Tonghui Wang^d, Grit Kupgan^d, Nora Schopp^a, Sangmin Chae^a, Veaceslav Coropceanu^d, Jean-Luc Brédas^d, Thuc-Quyen Nguyen^a, G. N. Manjunatha Reddy^b

^aCenter for Polymers & Organic Solids, University of California Santa Barbara, Santa Barbara, California 93106, United States

^bUniversity of Lille, CNRS, Centrale Lille Institut, Univ. Artois, UMR 8181, Unité de Catalyse et Chimie du Solide, Lille, France

^cCentre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz, Poland.

^dDepartment of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)

València, Spain, 2022 May 19th - 25th

Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson

Oral, G. N. Manjunatha Reddy, presentation 165
DOI: https://doi.org/10.29363/nanoge.hopv.2022.165
Publication date: 20th April 2022

Single-junction organic solar cells (OSCs) based on nonfullerene acceptors (NFAs) have recently seen dramatic increases in performance, with devices currently achieving over 18% power conversion efficiency (PCE).^[1-2] Since the introduction of “Y-series” NFAs, much effort has been expended to understand the reasons for their exceptional performance. While several studies have identified key optoelectronic properties that govern high PCEs, little is known about the molecular level origins of large variations in performance, spanning from 5% to 18% PCE, for example, in the case of OSCs based on PM6 donor polymer and Y6 acceptor. Here, we present a combined solid-state NMR, crystallography, and molecular modeling approach to elucidate the atomic-scale interactions in Y6 crystals, thin films, and PM6:Y6 bulk heterojunction (BHJ) blends (Figure 1).^[3] We will show the Y6 morphologies in BHJ blends are not governed by the morphology in neat films or Y6 single crystals. Notably, PM6:Y6 blends processed from different solvents self-assemble into different structures and morphologies, whereby the relative orientations of the sidechains and end groups of the Y6 molecules to their fused-ring cores play a crucial role in determining the resulting morphology and overall performance of the solar cells.^[4,5]

References

[1] C. Li, J. Zhou, J. Song, J. Xu, H. Zhang, X. Zhang, J. Guo, L. Zhu, D. Wei, G. Han, J. Min, Y.Zhang, Z. Xie, Y. Yi, H. Yan, F. Gao, F. Liu, Nat Energy 6, 605–613 (2021).

[2] Y. Cui, Y. Xu, H. Yao, P. Bi, L. Hong, J. Zhang, Y. Zu, T. Zhang, J. Qin, J. Ren, Z. Chen, C. He, X. Hao, Z. Wei, J. Hou, Adv. Mater. 2021, 33, 2102420.

[3] B. R. Luginbuhl, P. Raval, T. Pawlak, Z. Du, T. Wang, G. Kupgan, N. Schopp, S. Chae, S. Yoon, A. Yi, H. J. Kim, V. Coropceanu, 41 J.-L. Brédas, T.-Q. Nguyen, G. N. M. Reddy, Adv. Mater. 2022, 34, 2105943.

[4] A. Karki, J. Vollbrecht, A. J. Gillett, S. S. Xiao, Y. Yang, Z. Peng, N. Schopp, A. L. Dixon, S. Yoon, M. Schrock, H. Ade, G. N. M. Reddy, R. H. Friend, T.-Q. Nguyen, Energy Environ. Sci. 2020, 13, 3679.

[5] A. Karki, J. Vollbrecht, A. L. Dixon, N. Schopp, M. Schrock, G. N. M. Reddy, T. Nguyen, Adv. Mater. 2019, 31, 1903868.

References:

[1] 1. C. Li, J. Zhou, J. Song, J. Xu, H. Zhang, X. Zhang, J. Guo, L. Zhu, D. Wei, G. Han, J. Min, Y.Zhang, Z. Xie, Y. Yi, H. Yan, F. Gao, F. Liu, Non-fullerene acceptors with branched side chains and improved molecular packing to exceed 18% efficiency in organic solar cells. Nat Energy 6, 605–613 (2021).

[2] 2. Y. Cui, Y. Xu, H. Yao, P. Bi, L. Hong, J. Zhang, Y. Zu, T. Zhang, J. Qin, J. Ren, Z. Chen, C. He, X. Hao, Z. Wei, J. Hou, Single-Junction Organic Photovoltaic Cell with 19% Efficiency. Adv. Mater. 2021, 33, 2102420

[3] 3. B. R. Luginbuhl, P. Raval, T. Pawlak, Z. Du, T. Wang, G. Kupgan, N. Schopp, S. Chae, S. Yoon, A. Yi, H. J. Kim, V. Coropceanu, 41 J.-L. Brédas, T.-Q. Nguyen, G. N. M. Reddy, Resolving Atomic-Scale Interactions in Nonfullerene Acceptor Organic Solar Cells with Solid-State NMR Spectroscopy, Crystallographic Modelling, and Molecular Dynamics Simulations. Adv. Mater. 2022, 34, 2105943

[4] 4. A. Karki, J. Vollbrecht, A. J. Gillett, S. S. Xiao, Y. Yang, Z. Peng, N. Schopp, A. L. Dixon, S. Yoon, M. Schrock, H. Ade, G. N. M. Reddy, R. H. Friend, T.-Q. Nguyen, The role of bulk and interfacial morphology in charge generation, recombination, and extraction in non-fullerene acceptor organic solar cells, Energy Environ. Sci. 2020, 13, 3679

[5] 5. A. Karki, J. Vollbrecht, A. L. Dixon, N. Schopp, M. Schrock, G. N. M. Reddy, T. Nguyen, Understanding the High Performance of over 15% Efficiency in Single-Junction Bulk Heterojunction Organic Solar Cells. Adv. Mater. 2019, 31, 1903868.

Acknowledgements:

B.R.L., N.S., S.Y., S.C, T-Q.N., T.W., G.K., V.C., and J.L.B. gratefully acknowledge the financial support of the United States Department of the Navy, Office of Naval Research (Research Awards No. N00014-21-1-2181 and N00014-21-1-2182). T.W., G.K., V.C., and J.L.B. thank the DOD High Performance Computing Modernization Program for computational resources. Z.D. thanks the Air Force Office of Scientific Research (Grant No. FA9550-19-1-0348) for the financial support. G.N.M.R. acknowledges the financial support from University of Lille, IR-RMN-THC FR-3050 CNRS, and EU-H2020 (Grant No. 795091) for conducting ssNMR experiments. The computational resources were partially provided by the Polish Infrastructure for Supporting Computational Science in the European Research Space (PL-Grid).

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