A molecular interaction–diffusion framework for predicting organic solar cell stability
Harald Ade a
a Department of Physics, North Carolina State University
Online Conference
Proceedings of NFA-Based Organic Solar Cells: Materials, Morphology and Fundamentals (NFASC)
Online, Spain, 2021 February 3rd - 4th
Organizers: Natalie Banerji and Feng Gao
Invited Speaker, Harald Ade, presentation 012
DOI: https://doi.org/10.29363/nanoge.nfasc.2021.012
Publication date: 25th January 2021

The rapid increase in the power conversion efficiency of organic solar cells (OSCs) during the last few years has been achieved through 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 have remained elusive. The presentation will discuss the recent discovery that the diffusion of an NF-SMA into the donor polymer exhibits Arrhenius behavior and that the activation energy scales linearly with the enthalpic Flory-Huggins interaction parameters between the polymer and the NF-SMA. Consequently, the thermodynamically most unstable, hypo-miscible systems (high interaction parameter) are the most kinetically stabilized. In short, unfavorable interactions enable stability. We have also been able to relate the differences in Ea to measured and selectively simulated molecular self-interaction properties of the constituent materials that provide quantitative property–function relations that link thermal characteristics (glass transition) of the NF-SMA and mechanical characteristics of the polymer(elastic modulus) of the polymers [1]. This allows predicting relative diffusion properties and thus morphological stability from simple analytical measurements or molecular dynamic simulations.

 

All co-authors and funding agencies of the above cited reference are greatlfully acknowledged. 

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