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Hysteresis in phase volumes, compositions and interfacial roughness in model OPV-small-molecule/polymer thin-films
,
P. Gutfreund ,
VALERIA ITALIA,
A. Nelson ,
J. T. Cabral ,
Elizabeth Hynes
Soft Matter, Volume: 20, Issue: 11, Pages: 2532 - 2546
Swansea University Authors:
Anthony Higgins , VALERIA ITALIA, Elizabeth Hynes
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DOI (Published version): 10.1039/d3sm01066j
Abstract
Domain morphology and composition, and the structure of interfaces between domains are key factors in the performance and stability of organic photovoltaics (OPVs) fabricated from polymer/small-molecule blends. In this study, we investigate the evolution of composition, phase-volume and interfacial...
| Published in: | Soft Matter |
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| ISSN: | 1744-683X 1744-6848 |
| Published: |
Royal Society of Chemistry (RSC)
2024
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| Online Access: |
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa65633 |
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| Abstract: |
Domain morphology and composition, and the structure of interfaces between domains are key factors in the performance and stability of organic photovoltaics (OPVs) fabricated from polymer/small-molecule blends. In this study, we investigate the evolution of composition, phase-volume and interfacial roughness in model polymer/small-molecule bilayers, in response to thermal annealing. Polystyrene/fullerene mixing is studied as a function of annealing temperature, using in-situ neutron reflectivity, in thin-film bilayer samples comprising pure component or mixed layers. Remarkably, we discover that thermal annealing at temperatures around or above the reported glass transition temperatures, Tg, of the components can result in extensive mass-transfer between layers, that has the superficial appearance of equilibration, but leaves the layer compositions, thicknesses, and/or the interfacial composition profile in a non-equilibrium state. This is not merely a case of slow kinetics near Tg, as subsequent heating to higher temperatures, followed by cooling, reveals pronounced hysteresis in these systems. This has important implications for the measurement of equilibrium compositions in polymer/small-molecule mixtures for OPV applications, and for device stability during operation. |
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| Item Description: |
Data availability:Data can be downloaded using the DOIs for the two experiments: http://doi.ill.fr/10.5291/ILL-DATA.9-11-1903 and http://doi.ill.fr/10.5291/ILL-DATA.9-11-1983 after an embargo period of three years. Requests for data earlier than this should be emailed to the corresponding author. |
| College: |
Faculty of Science and Engineering |
| Funders: |
We thank the ILL for the award of beam time (experiment numbers 9-11-1903 in 2019 and 9-11-1983 in 2021), and the staff of D17 for help during the experiments. We thank the IT group at ILL for establishing remote access to D17, which was used during experiment 9-11-1983. AH thanks Josh Barlow and Ben Harrison at Swansea University for use of their chemistry facilities to host the sample preparation activity, which was necessitated following a fire in Swansea which closed the usual chemistry laboratory for more than a year. EH acknowledges Swansea University for funding her studentship. |
| Issue: |
11 |
| Start Page: |
2532 |
| End Page: |
2546 |