Dr N. Robertson

Dyes for Solar Cells

Conducting and Magnetic Materials

Dye-sensitised Solar Cells

Renewable energy sources including solar energy are set to play an increasing role as concerns about the environmental impact of mass power generation grow. Dye-sensitised photovoltaics is an extremely promising area that offers the possibility of cheap and efficient solar cells. These cells involve a dye that absorbs visible light and injects an electron into the conduction band of an inorganic semionductor such as TiO2. The oxidised dye is re-reduced by an electrolyte giving the required separation of the electron and the hole (Fig. 1). We are involed in the design, synthesis and characterisation of dyes with the appropriate spectroscopic and electrochemical properties to function in such cells (see for example Fig. 2). Work is currently aimed at the preparation of new dyes to allow construction of solar cells with better light-harvesting efficiency and stability. Dyes are characterised using electrochemistry, spectroelectrochemistry (UV/Vis/NIR; in situ EPR), emission spectroscopy, structural and computational methods. We prepare and study solar cells to test our dyes and collaborate with University of Bath, Imperial College London and other Universities for more detailed measurements, through the EPRSC Supergen Consortium.

Selected Recent References

(1) Elaine A. M. Geary, Keri L. McCall, Andrew Turner, Paul R. Murray, Eric J. L. McInnes, Lorna A. Jack, Lesley J. Yellowlees, Neil Robertson, Spectroscopic, Electrochemical and Computational Study of Pt-diimine-dithiolene Complexes: Rationalising the Properties of Solar Cell Dyes, Dalton Trans, 2008, 3701

(2) Neil Robertson, Catching the Rainbow: Light Harvesting in Dye-Sensitised Solar Cells, Angew. Chemie, 2008, 47, 1012

(3) K. L. McCall, J. R. Jennings, H. Wang, A. Morandeira, L. M. Peter, J. R.  Durrant, L. J. Yellowlees, J. D. Woollins, N. Robertson, Novel Ruthenium Bipyridyl Dyes with S-donor Ligands and their Application in Dye Sensitised Solar Cells, J. Photochem, Photobiol. A, 2009, 202, 196-204

Luminescent Solar Concentrator

A luminescent solar concentrator comprises a thin plastic sheet embedded with fluorescent dyes. The dyes absorb incoming sunlight and re-emit light at a longer wavelength. The re-emitted light is mostly trapped in the sheet by total internal reflection and is guided to the edges of the sheet. This allows comparatively expensive silicon solar cells to be placed only around the edge of the sheet, greatly reducing the total surface area required and effectively replacing these with a cheap plastic sheet. Figure 3 below shows the emission of light from the edge of a PMMA sheet containing an emissive dye prepared in our lab (Images taken by Dr Omar Moudam). We are working in collaboration with Anita Jones (Chemistry, University of Edinburgh) and Bryce Richards (Heriot Watt University) to optimise the chemical, photophysical and engineering aspects of these devices.

Fig. 3: Emitted light is mostly guided to the edge of the sheet which is seen to glow.

Selected Recent References

(1) Omar Moudam, Brenda. C. Rowan, Mohammed Alamiry, Patricia Richardson, Bryce. S. Richards, Anita C. Jones, Neil Robertson, Europium Complexes with High Total Photoluminescence Quantum Yields in Solution and in PMMA, Chem. Commun, 2009, 6649

(2) Brenda Rowan, Bryce S. Richards, Neil Robertson, Anita Jones, Patricia Richardson, Omar Moudam, Near Infrared Emitting Lanthanide Complexes for Luminescent Solar Concentrators, 23^rd European Photovoltaic Conference, 2008, 1 – 5 Sep, Valencia, Spain