Issue 48, 2018

Impact of solution temperature-dependent aggregation on the solid-state packing and electronic properties of polymers for organic photovoltaics

Abstract

The performance of a bulk-heterojunction organic solar cell critically depends on the morphology of the active layer. The solution temperature-dependent aggregation characteristics of a series of polymer donors have been recently exploited as an effective protocol for morphology control in high-efficiency devices. Here, we use an approach combining molecular dynamics simulations and long-range corrected density functional theory calculations to investigate the impact of solution temperature-dependent aggregation on the polymer solid-state packing and electronic properties. We consider two representative polymer systems: (i) PffBT4T-2OD (poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3′′′-di(2-octyldodecyl)-2,2′;5′,2′′;5′′,2′′′-quaterthiophen-5,5′′′-diyl)]), and (ii) PBT4T-2OD (poly[(2,1,3-benzothiadiazole-4,7-diyl)-alt-(3,3′′′-di(2-octyldodecyl)-2.2′;5′,2′′;5′′,2′′′-quarterthiophen-5,5′′′-diyl)]), where the fluorine atoms on the benzothiadiazole moieties of PffBT4T-2OD are replaced with hydrogen atoms. We find that both temperature-dependent aggregation and the presence of fluorine atoms are important in determining the nature of the solid-state packing and the electronic properties in the polymer phases. Our results are consistent with the experimental data that show that PffBT4T-2OD aggregates at lower temperatures and leads to higher OPV efficiency.

Graphical abstract: Impact of solution temperature-dependent aggregation on the solid-state packing and electronic properties of polymers for organic photovoltaics

Supplementary files

Article information

Article type
Paper
Submitted
24 Okt 2018
Accepted
19 Nov 2018
First published
20 Nov 2018

J. Mater. Chem. C, 2018,6, 13162-13170

Author version available

Impact of solution temperature-dependent aggregation on the solid-state packing and electronic properties of polymers for organic photovoltaics

A. Ashokan, T. Wang, M. K. Ravva and J. Brédas, J. Mater. Chem. C, 2018, 6, 13162 DOI: 10.1039/C8TC05378B

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