STMicroelectronics (distributed by Braemac ) is funding a solar cell research program that aims to reduce the costs of generating electricity from solar power to allow it to compete with conventional electricity generation.
The company says existing solar cell technologies are based on expensive high purity semiconductor materials such as silicon that have made them too costly to be commercially viable. Consequently, although the sunlight “fuel” is free, the overall cost of solar-generated electricity (amortised over the typical 20 year lifetime of a solar cell) is around ten times higher than the cost of electricity generated by, for example, the burning of fossil fuels.
ST research teams based in Catania and Naples, Italy, however, will exploit the semiconductor company’s expertise in nanotechnology in the quest to develop solar cell (or photovoltaic) systems capable of converting sunlight into electrical power to new levels of cost efficiency.
Although conventional semiconductor-based solar cells do offer a high energy conversion efficiency level (defined as the electrical energy produced for a given input of solar energy) there is little room for improvement - particularly in terms of manufacturing cost. ST is therefore pursuing alternative approaches in which the aim is to produce solar cells that have lower conversion efficiencies (for example 10% instead of 15-20%) but are significantly cheaper to manufacture.
The company is following two approaches. The first uses a similar principle to photosynthesis where what is called a “Dye-Sensitised Solar Cell” (DSSC) exploits an organic dye (photosensitiser) to absorb the light and create electron-hole pairs, a nanoporous (high surface area) metal oxide layer to transport the electrons, and a hole-transporting material, which is typically a liquid electrolyte.
The second approach is based on developing low cost solar cells using a full organic approach, in which a mixture of electron-acceptor and electron-donor organic materials are sandwiched between two electrodes. The nanostructure of this blend is said to be crucial for the cell performance because the electron-donor and electron-acceptor materials have to be in intimate contact at distances below 10 nm.