Tsoi, W C; James, D T*; Kim, J S*; Nicholson, P G; Murphy, C E; Bradley, D D C*; Nelson, D*; Kim, J S* (2011) The nature of in-plane skeleton Raman modes of P3HT and their correlation to the degree of molecular order in P3HT:PCBM blend thin films. J. Am. Chem. Soc., 133 (25). pp. 9834-9843.

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Abstract

The nature of main in-plane skeleton Raman modes (C=C and C-C stretch) of poly(3-hexylthiophene) (P3HT) in pristine and its blend thin films with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is studied by resonant and non-resonant Raman spectroscopy and Raman simulations. The ordered phase of P3HT with respect to its disordered phase is identified by (a) a large redshift in the C=C mode peak position, (b) a narrower FWHM of the C=C mode, (c) a large intensity of the C-C mode relative to the C=C mode and (d) a very small Raman dispersion of the C=C mode. The behaviour of the C=C and C-C modes of the ordered and disordered phases of P3HT can be explained in terms of different molecular conformations. The C=C Raman mode of P3HT in P3HT:PCBM blend films can thus be reproduced by simple superposition of the two peaks observed in different phases of P3HT (ordered and disordered). Based on the significantly different Raman characteristics between ordered and disordered phases of P3HT under resonant conditions, we quantify the effect of blending with PCBM and the subsequent thermal annealing on molecular order of P3HT to be 40% and 95% in terms of the fraction of ordered P3HT phase, respectively. We demonstrate that Raman spectroscopy (particularly in resonant region) is a simple and power technique to study molecular order of conjugated polymers and their blend films.

Item Type:	Article
Keywords:	poly(3-hexylthiophene) (P3HT), [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), resonant Raman spectroscopy, molecular order
Subjects:	Advanced Materials Advanced Materials > Photovoltaics
Identification number/DOI:	10.1021/ja2013104
Last Modified:	02 Feb 2018 13:14
URI:	http://eprintspublications.npl.co.uk/id/eprint/5194

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