Novel solar cell could break conversion efficiency barrier

‘This research has produced a novel, realistically achievable, lattice-matched, multi-junction solar cell design with the potential to break the 50 per cent power conversion efficiency mark under concentrated illumination,’ said Robert Walters, PhD, NRL research physicist. ‘At present, the world record triple-junction solar cell efficiency is 44 per cent under concentration and it is generally accepted that a major technology breakthrough will be required for the efficiency of these cells to increase much further.’

The work was carried out in collaboration with Imperial College London and MicroLink Devices.

According to NRL, each junction in multi-junction (MJ) solar cells is tuned to different wavelength bands in the solar spectrum to increase efficiency.

High-band-gap semiconductor material is used to absorb the short-wavelength radiation with longer-wavelength parts transmitted to subsequent semiconductors.

In theory, an infinite-junction cell could obtain a maximum power conversion percentage of nearly 87 per cent. The challenge is to develop a semiconductor material system that can attain a wide range of band gaps and be grown with high crystalline quality.