Ionic liquids for solar cells

G24 Innovations and BASF are to work together to develop ionic liquids to improve both the performance and efficiency of G24i’s solar cells.

Welsh solar-cell outfit G24 Innovations (G24i) and BASF are to work together to develop ionic liquid formulations that further improve the performance and efficiency of G24i’s solar cells which use a proprietary dye sensitised thin-film technology.

Dye sentisitised solar cells are photoelectrochemical cells that use photo-sensitisation of wide-band-gap mesoporous oxide semiconductors. The cells were invented by Michael Graetzel in 1988 and are also known as “Graetzel cells”. The cells are extremely promising because they are made of low-cost materials and do not need elaborate apparatus to manufacture.

The cells have a simple structure that consists of two electrodes and an iodide-containing electrolyte. One electrode is dye-absorbed highly porous nanocrystalline titanium dioxide (nc-TiO2) deposited on a transparent electrically conducting substrate. The other is a transparent electrically conducting substrate only.

The cells have been compared to photosynthesis because they use the redox reaction of the electrolyte. However, the energy conversion efficiency of the cells has not yet reached the level of silicon solar cells – the current energy conversion efficiency is about 10 per cent. Notwithstating, G24i has developed an automated “roll-to-roll” manufacturing process that can transform a lightweight roll of metal foil into a 100-pound half-mile of dye-sensitised thin film in less than three hours.

The photovoltaic cells are sensitive to far more of the visible spectrum of light than conventional solar cells, so that all sorts of light sources can be used to generate power, even at relatively low levels of light intensity.

Whilst G24i is developing solar products to power a range of portable electronics,  BASF is manufacturing the ionic liquids – salts which are liquid below 100°C – which are used in them.

‘Whilst BASF has been a supplier of ionic liquids to G24i for some time, this new agreement will allow us to work more closely on the selection of suitable formulations that we will test at our specialist facility. We will share the results of these tests and work with BASF to continuously enhance the quality of our product,’ said Clemens Betzel, President of G24i.