Spray-On Solar Cells Pursued

Creating solar cells you can wear, fold and bend – even spray onto surfaces – is the goal of a four-year research program set to begin next month under a consortium of eight UK universities.

The £3.4 million (about $4.7 million) SUPERGEN Excitonic Solar Cell Consortium is funded by the Engineering and Physical Sciences Research Council (EPSRC) and brings together the universities of Warwick, Bath, Bristol, Cambridge, Edinburgh, Imperial College, Loughborough and Oxford.

The University of Warwick is leading the effort to prepare and characterize new solar cells using the processes of light absorption, exciton movement and current generation, which can be studied on a time scale extending down to femtoseconds (quadrillionths of a second).

This excitonic solar cell, based on conjugated polymers, shows the simple sandwich structure. The active layer is a mixture of two polymers that separate to give a nanostructured interface. (Image: EPSRC)

Standard solar cells tend to be heavy and are silicon-based, while excitonic solar cells (ESCs) are made from organic compounds, dyes, gels or liquids. Light absorption leads to electronically excited molecular states called excitons. Excitons transfer energy between molecules for a few tens of nanometers until they reach an interface between two materials where the energy is used to create an electron in one material (phase) and a hole in the other, creating current.

They can be made using low-cost methods that could deposit or even spray onto both rigid and flexible bases. One could wear them, use them to power electronic products bent to fit a space or a body shape, or even spray them onto the roof of a vehicle that could easily not take the weight of conventional solar cells.

“There have also been initial steps to commercialize some ESCs, with the first manufacturing plant to produce dye-sensitized excitonic cells opening in the UK in 2007,” said lead researcher and University of Warwick research chemist Tim Jones. “However, it is widely recognized that much fundamental research still needs to be carried out, in particular on the less well developed organic and hybrid excitonic cells.”

Under the program, Bath and Imperial College are developing dye-sensitized and nanoparticle-sensitized solar cells, while Cambridge and Imperial College are investigating organic solar cells, including polymer blends, molecular heterojunctions and hybrid organic/inorganic systems. Edinburgh’s contribution is in the molecular design and synthesis of new materials such as dyes and hole-transporting organic compounds.

For more information, visit: www2.warwick.ac.uk