Project R-4893

Molecular mixing in bulk heterojunction organic solar cells - nanomorphology vs performance (Research)

The photovoltaic behavior of organic bulk heterojunction (BHJ) blends of conjugated (donor) polymers and fullerene (acceptor) derivatives has been subject of many studies in fundamental chemistry and physics since its initial discovery in 1995. From the general understanding at this moment, the nanomorphology of the active layer blend seems to be crucial. The latter is the result of a complex process in which phase separation and crystallization, thermodynamics and kinetics are key aspects. At present, fundamental understanding at the molecular level is limited. The main aim of the project is therefore to unravel nanomorphology formation at the molecular level and its effect on device performance beyond state of the art by an integrated experimental effort, combining the study of blends via advanced thermal analysis and solid-state NMR techniques with in situ analysis of the optoelectronic characteristics in photovoltaic devices. The materials under study are donor-acceptor alternating copolymers of which the side chain pattern and molecular weight are systematically varied. In combination with known fullerenes, intercalation phenomena are studied and interpreted in function of an integrated model based on the results of said measurements, combined with additional support from theoretical modelling and 3D-TEM/EELS data. The deeper insights so obtained may lead to molecular structure engineering in function of the desired nanomorphology and thus wanted photovoltaic parameters.

01 January 2014 - 31 December 2017