Structural properties of polymer bulk heterojunction (BHJ),  microstructure of the donor–acceptor blends

Conjugated polymer-based photovoltaics have become the subject of intense research as they have displayed significant potential for competition with conventional inorganic-based solar cells. The poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend is one of the most promising and most studied organic photovoltaic bulk heterojunction(BHJ) solar cell material so far. Using high probe techniques such as grazing incidence X-ray diffraction (GIXD), we investigate the structural properties of the blends and its dependence on temperature; and thus efficiency of the final cell.

In previous studies, we investigated blend structure before and after annealing. This has allowed us to understand the effect of thermal annealing on blend morphology.

christelle_2d_image_blends

The 2D images show an improvement in P3HT crystallinity after annealing; which may result in an increase of device performance. Looking at the out-of-plane profiles, we see for both blends clearly defined (h00) peaks. But more remarkable was the (020) peak which is almost inexistent for the as-cast film.

christelle_lineprofiles_blends

Presently, my work is oriented towards in-situ studies with the aim of getting more insight into the crystallization state of polymer blends for organic solar cells.

 
DMS