Ionic liquids for 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.