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Oral 28
Abstract
DYNAMICS OF P3HT IN HOMOPOLYMERS AND BLENDS
BY 1 H AND 13 C RELAXATION
Marco Geppi,* ,a Francesca Martini, a Silvia Borsacchi, a Silvia Spera b
a) Dipartimento di Chimica e Chimica Industriale, Università di Pisa, v. Risorgimento 35, 56126
Pisa (Italy);
b) Centro Ricerche Per Le Energie Non Convenzionali, Istituto ENI Donegani, ENI S.p.A., Via G.
Fauser 4, 28100 Novara (Italy);
email: mg@dcci.unipi.it
ABSTRACT
Polymeric solar cells (PSC’s), characterized by low-cost polymeric photoactive layers, are arising a
great interest in the field of solar energy, but several issues, such as the efficiency of these devices,
need to be improved before their industrial breakthrough can take place [1]. The investigation of the
morphology <strong>and</strong> dynamics of the polymeric photoactive layers <strong>and</strong> of the correlations between
these properties <strong>and</strong> the efficiency of the final PSC’s is considered of primary importance in order
to develop systems with improved <strong>and</strong> optimized performances. To this aim solid-state NMR
(SSNMR) is one of the most promising techniques, as demonstrated by the increasing number of
applications in the field [2, 3, 4].
Blends of poly(3-hexylthiophene) (P3HT), as electron-donor, <strong>and</strong> [6,6]-phenyl-C 60 -butyric acid
methyl ester (PCBM), as electron-acceptor are one of the most performing photoactive materials
developed so far, <strong>and</strong> were object of several studies in the literature [2, 3]. In this work we
investigated in detail the dynamic properties of P3HT in the frequency range of MHz in both the
neat polymer <strong>and</strong> the photoactive blends P3HT/PCBM before <strong>and</strong> after annealing with the final aim
to find correlations between these properties <strong>and</strong> the efficiency of the correspondig devices. In
particular, 1 H <strong>and</strong> 13 C T 1 's were measured at different temperatures by means of low-resolution <strong>and</strong>
high-resolution experiments, respectively, <strong>and</strong> were simultaneoulsly fitted by means of a suitable
model using a home-made software. This analysis allowed the main reorientational motions of
P3HT alkylic side-chains <strong>and</strong> the twisting motion of P3HT main-chain to be characterized, <strong>and</strong> the
corresponding correlation times <strong>and</strong> activation energies to be quantitatively determined. Moreover,
the phase separation behaviour of the blends were investigated by following the proton spin
diffusion process through proton spin-lattice relaxation times.
Comparing the results obtained for the neat P3HT <strong>and</strong> the P3HT/PCBM blends, it was found that
the dynamic behaviour of P3HT significantly changes among the different systems, <strong>and</strong> possible
correlations between the mobility of P3HT side-chains in the blends before <strong>and</strong> after annealing, the
phase separation behaviour, <strong>and</strong> the increase of efficiency of the final PSC following annealing
were proposed [5].
References
[1] R. Po, M. Maggini, <strong>and</strong> N. Camaioni J. Phys. Chem. C 114, 695-706 (2010)
[2] C. Yang, J. G. Hu, <strong>and</strong> A. J. Heeger J. Am. Chem. Soc. 128, 12007-12013 (2006)
[3] R. Mens, F. Demir, G. Van Assche, B. Van Mele, D. V<strong>and</strong>erz<strong>and</strong>e, P. Adriaensens J. Polym. Sci. Pol. Chem. 50,
1037-1041 (2012)
[4] S. Chambon, R. Mens, K. V<strong>and</strong>ewal, E. Clodic, M. Scharber, L. Lutsen, J. Gelan, J. Manca, D. V<strong>and</strong>erz<strong>and</strong>e, P.
Adriaensens Sol. Energ. Mat. Sol. C 96, 210-217 (2012)
[5] F. Martini, S. Borsacchi, S. Spera, C. Carbonera, A. Cominetti, M. Geppi J. Phys. Chem. C 117, 131-139 (2013)
<strong>8th</strong> <strong>Conference</strong> on Fast Field Cycling NMR Relaxometry, Turin 23-25 May 2013