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Proceedings Paper

2D compact model to characterize phase separation in organic solar cell bulk heterojunctions (Conference Presentation)
Author(s): Franklin L. Lee; Amir Barati Farimani; Kevin L. Gu; Hongping Yan; Zhenan Bao; Vijay S. Pande

Paper Abstract

The phase separation between donor and acceptor molecules within the active layer of an organic solar cells dictates the morphology and hence is key to the recombination rate and ultimately the performance of the organic solar cell. Molecular dynamics (MD) simulation is a suitable technique to understand this phenomenon; however, conventional all-atom MD simulations cannot reach the appropriate length and time scales to compare with macroscopic observation. Even with the many available coarse-grained MD models, it is difficult to reach these scales. Therefore, we introduce here a 2D compact model to overcome this challenge, built by multiscale coarse-graining. First, we simulate systems including conjugated polymers, fullerenes, and organic solvents using all-atom MD to extract information about molecular conformation and packing. This includes an analysis of polymer solution behavior, fullerene clustering, and binary and tertiary mixing properties. These results are then used to systematically parameterize the molecules used in 2D coarse-grained MD simulations. The 2D simulations probe experimentally relevant length scales that were previously intractable to sample by other MD simulation methods. Using this model, we explore ternary systems including polymer, fullerene, and solvent molecules to investigate the phase separation process between polymer donors and fullerene acceptors. In this scheme, we additionally introduce explicit solvent evaporation to emulate realistic processing conditions. We quantify phase separation domain sizes that are comparable to experimentally observed values from resonant soft x-ray scattering. In addition, we extend this framework to other chemical species to demonstrate the flexibility of the approach.

Paper Details

Date Published: 19 September 2017
Proc. SPIE 10363, Organic, Hybrid, and Perovskite Photovoltaics XVIII, 1036305 (19 September 2017); doi: 10.1117/12.2273045
Show Author Affiliations
Franklin L. Lee, Stanford Univ. (United States)
Amir Barati Farimani, Stanford Univ. (United States)
Kevin L. Gu, Stanford Univ. (United States)
Hongping Yan, Stanford Synchrotron Radiation Lightsource (United States)
Zhenan Bao, Stanford Univ. (United States)
Vijay S. Pande, Stanford Univ. (United States)
Andreessen Horowitz (United States)

Published in SPIE Proceedings Vol. 10363:
Organic, Hybrid, and Perovskite Photovoltaics XVIII
Zakya H. Kafafi; Paul A. Lane; Kwanghee Lee, Editor(s)

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