Abstract
Rapid increase in the power conversion efficiency of organic solar cells (OSCs) has been achieved with the development of non-fullerene small-molecule acceptors (NF-SMAs). Although the morphological stability of these NF-SMA devices critically affects their intrinsic lifetime, their fundamental intermolecular interactions and how they govern property-function relations and morphological stability of OSCs remain elusive. Here, we discover that the diffusion of an NF-SMA into the donor polymer exhibits Arrhenius behaviour and that the activation energy E$_{a}$ scales linearly with the enthalpic interaction parameters χ$_{H}$ between the polymer and the NF-SMA. Consequently, the thermodynamically most unstable, hypo-miscible systems (high χ) are the most kinetically stabilized. We relate the differences in E$_{a}$ to measured and selectively simulated molecular self-interaction properties of the constituent materials and develop quantitative property-function relations that link thermal and mechanical characteristics of the NF-SMA and polymer to predict relative diffusion properties and thus morphological stability.
| Original language | English (US) |
|---|---|
| Journal | Nature materials |
| DOIs | |
| State | Published - Jan 12 2021 |
Bibliographical note
KAUST Repository Item: Exported on 2021-02-04Acknowledged KAUST grant number(s): N000141712204
Acknowledgements: Y.Q., Z.P., H.H., H.A. and initial work by M.G. was supported by Office of Naval Research (ONR) grant no. N000141712204 and KAUST’s Center Partnership Fund (no. 3321). N.B. and B.T.O. acknowledge support by a National Science Foundation (NSF) grant (no. CMMI-1554322). T.K., A.A. and recent work by M.G. was supported by NCSU start-up funds to A.A., J.R. and W.Y. acknowledge support by an NSF grant (no. CBET-1639429). C.R. and W.M. acknowledge the support of the ONR (N00014-18-1-2448) and the NSF under Cooperative Agreement no. 1849213; supercomputing resources were provided by the Department of Defense (DoD) through the DoD High-Performance Computing Modernization Program (project no. ONRDC40433481) and by the University of Kentucky Information Technology Department and Center for Computational Sciences. SIMS measurements were performed at the Analytical Instrumentation Facility at NCSU, which is partially supported by the State of North Carolina and the National Science Foundation. C. Zhou is acknowledged for providing support for SIMS measurements. The DSC instrument was purchased with UNC-GA ROI funds. C. Zhu, A. Hexemer and C. Wang of the ALS provided instrument maintenance. E. Gomez and J. Litofsky are acknowledged for providing the initial Flory–Huggins program code. L. Ye and M. Balik (NCSU) are acknowledged for fruitful discussion and input. A. Dinku is acknowledged for maintaining shared ORaCEL facilities and sharing some PBDB-T2F:Y6 stability data for reference. F. He and T. Zhao are acknowledged for help with attaining molecular weight data via high temperature gel permeation chromatography. H. Yan is acknowledged for providing ITIC-4Cl NF-SMA. I. Angunawela is acknowledged for performing complementary shelflife measurements of P3HT:EH-IDTBR devices.