R.A.J. Janssen

Realization of large area flexible fullerene-conjugated polymer photocells: A route to plastic solar cells

Various interesting photophysical phenomena in composites of fullerenes and non degenerate ground state conjugated polymers with highly extended π-electrons in their main chain can be explained by the ultrafast electron transfer from the conjugated polymer (donor) to the fullerene (acceptor) upon illumination. This photoeffect was utilized for the production of small area (mm2) photovoltaic devices which show energy conversion efficiencies ηe>1% and carrier collection efficiencies ηc>20%. In this work we present efficiency and stability studies on large area (6 cm by 6 cm) flexible solar cells based on a soluble alkoxy PPV (3,7-dimethyloctyloxy methyloxy poly(phenylenevinylene)) and a highly soluble fullerene derivative, 1-(3-methoxycarbonyl)propyl-1 phenyl [5,6]C61 (PCBM). The enhanced solubility of PCBM compared to C60 allows a high fullerene-conjugated polymer ratio and strongly supports the formation of donor-acceptor bulk heterojunctions.

Combinatorial Chemistry Approach to Development of Molecular Plastic Solar Cells

We used a combinatorial chemistry approach to develop the molecular plastic solar cells based on soluble fullerene derivatives or solubilized TCNQ molecules in combination with conjugated polymers. Profiles, formed by the diffusion of low molecular weight component in the spin-cast polymer host were used. The ratio between low molecular weight acceptor and polymer changed along the diffusion gradient direction from 100% to 0% at the distances 10-20 mm. Optical and electrophysical properties such as absorption, luminescence, short circuit current and open circuit voltage were measured using a specially designed installation with the resolution of 25 points per millimetre.

Oligomer-fullerene dyads and triads as model compounds for bulk-heterojunction PV cells

Covalent oligomer-fullerene donor-acceptor structures can serve as important model systems for plastic PV cells, based on interpenetrating networks of conjugated polymers and fullerene derivatives. Several series of [60]fullerene-oligomer dyads and triads were prepared. Photoinduced electron transfer phenomena were studied using photoinduced absorption spectroscopy. Measurements in solution and in the solid state reveal that the environment plays a crucial role in the formation and lifetime of the photoinduced charged states in these molecules.