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Dynamics of Crystallization and Disorder during Annealing of P3HT/PCBM Bulk Heterojunctions

DOI: 10.1021/ma102817z DOI Help

Authors: Samuele Lilliu (Cardiff University) , Tiziano Agostinelli (Imperial College London) , Ellis Pires (University of Cardiff) , Mark Hampton (University of Cardiff) , Jenny Nelson (Imperial College London) , Emyr Macdonald (Cardiff University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Macromolecules , VOL 44 (8) , PAGES 2725 - 2734

State: Published (Approved)
Published: April 2011

Abstract: A real-time crystallographic analysis of P3HT/PCBM films during thermal annealing is reported, detailing the temporal variation of crystallization, disorder, and orientational spread during the annealing. Five P3HT/PCBM chlorobenzene solutions with different P3HT concentrations (0, 33, 50, 67, 100 wt %) were spin coated on SiO2 substrates. The thick films (?100 nm) were studied during annealing (50 min at 140 °C), with in situ synchrotron grazing incidence X-ray diffraction (GI-XRD) and a sampling time <8 s. For the first time, the evolution of the crystal structure is analyzed taking into account P3HT paracrystallinity. The following were observed: a predominance of edge-on P3HT lamellae in the as-spun and annealed films; changes in concentration-dependent edge-on lamellar orientation spread along the alkyl-stacking direction and paracrystalline disorder after annealing; a permanent lamellar stretching just along the alky-stacking direction after annealing; an increase in the P3HT domain size along only the alkyl-stacking direction for the edge-on lamellae, with dynamics consistent with PCBM acting as a plasticizer for P3HT; and finally, an increase in the PCBM concentration at the sample?air interface. We show that the paracrystalline correction is important to calculate correctly the domain size as deduced from GI-XRD.

Subject Areas: Materials, Energy


Instruments: I07-Surface & interface diffraction