Associate Professor Roger Reeves...

Professor Reeves has been successfully looking at the properties of indium nitride and zinc-oxide that have the potential to significantly improve the efficiency of optoelectronic devices.

“Silicon solar cells are used to convert sunlight into electricity but can only achieve a maximum efficiency of around 35 per cent because they treat all wavelengths of sunlight equally – the high energy blue sunlight is treated the same as the lower energy red light. By being cleverer about the way the solar cell is constructed it becomes possible to get close to 100 per cent efficiency – but that requires the development of new semiconductor materials.”

“Zinc oxide is a bizarre material that we know very well — it’s a common ingredient in sunblock and nappy-rash creams. It is also a by-product of copper smelting and thus has a history of thousands of years. However, what has been realised in recent times is that zinc oxide has optical and electronic properties that (in theory) make it better suited for UV or white light-emitting devices than current materials.

“To see why this may be important we only need to look at the transformation of traffic lights. Five years ago a green traffic light consisted of a white light behind a green piece of glass. Most of the energy of the lamp was lost. Today we see traffic lights made of an array of green or yellow or red light-emitting diodes (LEDs). These LEDs are designed to emit light of only the colour wanted and thus there is very little energy wasted.”

In a country such as Japan, the conversion of traffic and railway lights to LED technology has dramatically altered the need for new power stations. That can have a big impact on the environment in reducing CO2 emissions, Professor Reeves said.

http://www.comsdev.canterbury.ac.nz/news/2007/071109a.shtml