Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/31178
Title: Phase Behavior in the Active Layer of Small Molecule Organic Photovoltaics: State Diagram of p-DTS(FBTTh2)(2):PC71BM
Authors: Van den Brande, Niko
Defour, Maxime
DEVISSCHER, Dries 
VERSTAPPEN, Pieter 
REEKMANS, Gunter 
D'HAEN, Jan 
ADRIAENSENS, Peter 
MAES, Wouter 
Van Assche, Guy
Van Mele, Bruno
Issue Date: 2020
Publisher: AMER CHEMICAL SOC
Source: JOURNAL OF PHYSICAL CHEMISTRY C, 124 (13) , p. 7566 -7577
Abstract: A comprehensive study was undertaken to obtain a more fundamental understanding of the phase behavior of the p-DTS-(FBTTh2)(2):PC71BM system, used in small molecule organic solar cells, with a strong focus on the amorphous phase and its influence on crystallinity. Three dedicated thermal protocols were used in combination with advanced thermal analysis, solid-state NMR, and wide-angle X-ray diffraction. Rapid cooling, to avoid structure formation and gain insight in the amorphous phase, and slow cooling, to promote structure formation, were used as limiting cases to explain the intermediate behavior after device processing from solution. A complete state diagram was developed, and the glass transition (T-g)-composition relationship was determined. In the case of slow cooling and the procedure used for device processing, the rapid crystallization of p-DTS(FBTTh2)(2) leads to an enrichment of the amorphous phase in PC71BM, increasing its T-g and causing vitrification of the mixed amorphous phase before crystallization when the total amount of PC71BM exceeds 70 wt %. The common processing additive 1,8-diiodooctane (DIO) was found to lead to a lower p-DTS(FBTTh2)(2) crystallinity and smaller average crystal size. More importantly, it acts as a strong plasticizer, lowering T-g significantly and thus reducing the morphological stability of the p-DTS(FBTTh2)(2):PC71BM mixtures.
Notes: Van den Brande, N (reprint author), Vrije Univ Brussel, Phys Chem & Polymer Sci FYSC, B-1050 Brussels, Belgium.
npvdbran@vub.be
Other: Van den Brande, N (reprint author), Vrije Univ Brussel, Phys Chem & Polymer Sci FYSC, B-1050 Brussels, Belgium. npvdbran@vub.be
Keywords: Solar-Cells;Glass-Transition;Isothermal Crystallization;Performance;Blends;Impact;Efficiency;Semiconductors;Morphology;Polymers
Document URI: http://hdl.handle.net/1942/31178
ISSN: 1932-7447
e-ISSN: 1932-7455
DOI: 10.1021/acs.jpcc.0c00808
ISI #: WOS:000526328500063
Rights: 2020 American Chemical Society
Category: A1
Type: Journal Contribution
Validations: ecoom 2021
Appears in Collections:Research publications

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