One of the UK's largest photovoltaic (PV) solar cell research projects, PV-21, is investigating a replacement for indium, a rare metal used in the absorbing semiconductors and transparent conductors of many solar cells that costs around £320/kg. Almost 50t of the material is required to create enough solar panels to provide one gigawatt of energy, therefore a cheaper alternative is vital.
‘For a transparent conductor, you need a material that has an exceptional combination of properties, including optical transparency and electrical conductivity,’ says the project’s principal investigator, Professor Ken Durose of Durham University, UK. ‘For absorbing materials, copper indium diselenide is the archetype, but there are alternatives, such as copper indium gallium diselenide, in which the band gap has been tuned a little. Those are interesting materials, but they are compounds of indium. So our first direction is to find alternatives.’
Researchers will also attempt to control the crystal growth process of the cell’s polycrystalline thin films. This could reduce incongruities, allowing thinner cells, down to one-micron thick, to be created (compared to conventional six-to-eight-micron thick cells).
The £6.3m collaborative project, funded by the EPSRC as part of the SUPERGEN bioenergy R&D consortium, includes experts from the universities of Bangor, Bath, Cranfield, Edinburgh, Northumbria, Southampton and Imperial College London, alongside nine industrial partners, including Millbrook Instruments and Crystalox. Its second phase is set to begin in April 2008 and will last for four years.