Clustering of High Molecular Weight PCDTBT in Bulk-Heterojunction Casting Solutions

Clulow, Andrew J., Gilbert, Elliot P., Wolfer, Pascal, Burn, Paul L. and Gentle, Ian R. (2015) Clustering of High Molecular Weight PCDTBT in Bulk-Heterojunction Casting Solutions. Macromolecules, 48 22: 8331-8336. doi:10.1021/acs.macromol.5b02040

Author Clulow, Andrew J.
Gilbert, Elliot P.
Wolfer, Pascal
Burn, Paul L.
Gentle, Ian R.
Title Clustering of High Molecular Weight PCDTBT in Bulk-Heterojunction Casting Solutions
Journal name Macromolecules   Check publisher's open access policy
ISSN 1520-5835
Publication date 2015-11-12
Year available 2015
Sub-type Article (original research)
DOI 10.1021/acs.macromol.5b02040
Open Access Status Not yet assessed
Volume 48
Issue 22
Start page 8331
End page 8336
Total pages 6
Place of publication Washington, DC, United States
Publisher American Chemical Society
Language eng
Formatted abstract
The narrow optical gap conjugated polymer poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) has been used as the electron donor material in efficient solution-processed bulk-heterojunction (BHJ) photovoltaic and photodetector devices when blended with fullerene derivatives. It was found that the solution viscosity used to form the active films could be controlled by the cooling rate of a hot solution of the materials and that fast-cooled solutions afforded more efficient bulk-heterojunction solar cells than their slow-cooled counterparts. Viscometry measurements showed that the rheological behavior of the solutions is modeled by the Martin equation for different PCDTBT molecular weights and temperatures. The Martin constant KM that describes the interpolymer interactions in solution was found to increase with polymer molecular weight and decrease with increasing temperature in an analogous manner to the Flory–Huggins interaction parameter χ. Small-angle neutron scattering (SANS) was used to show that when hot solutions of the polymer were cooled, phase separation into polymer-rich clusters and solvent-rich domains occurred. Similar phase separation was observed in the case of blend solutions. In addition, the fast-cooled solutions trapped more 70-PCBM in the polymer-rich phase, which in turn made the structure of the polymer more rodlike in the clusters. The results provide an explanation as to why fast-cooled solutions lead to devices with greater efficiency.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Centre for Organic Photonics and Electronics
Official 2016 Collection
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Citation counts: TR Web of Science Citation Count  Cited 2 times in Thomson Reuters Web of Science Article | Citations
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