W.C.Tsai and M.O'Neill of the department of Physics, Hull University in the UK and M.P.Aldred, P.Vlachos and S.M.Kelly of the Department of Chemistry of the same university have just reported a new form of organic photovoltaics.
They studied a novel electron–donating reactive mesogen (polymerisable liquid crystal) (RM) and an electron–accepting perylene glass used to demonstrate a new photovoltaic concept. A liquid crystal gel consisting of a phase–separated mixture of the two materials is used to template a nanoporous surface which provides a distributed interface in a bilayer organic photovoltaic.
The nanogrooved interface is obtained by photopolymerising the RM and then washing away the perylene droplets. For optimum performance the spatial scale of the grooves should match the exciton diffusion length and the grooves should penetrate across most of the layers. A photoinduced absorption (PIA) experiment was used to probe and characterise electron transfer between the RM and perylene materials.
Their conclusions were - The novel materials are a promising electron donor and acceptor pair for photovoltaics since there is fast photoinduced electron transfer from the RM to the perylene with slow charge recombination rate at 80K.
Nanoscale out–plane and in–plane topography was obtained using the "gel method". This template has the potential for efficient charge separation and charge transport when the perylene is deposited on top of it. Further work is required to increase the in–plane spatial frequencies so all photogenerated excitons reach the interface before recombination.
Nematic liquid crystal gels are a novel approach to organic photovoltaics, as confirmed by preliminary results.
Image Source: University of Hull