Boffins create cheaper, lighter ultra thin solar cells

London : US researchers claim to have created an ultra thin solar cell that could provide a cheaper, lighter alternative to similar existing devices.

James Zahler from Aonex Technologies, together with colleagues from the California Institute of Technology and EMCORE PhotoVoltaics made the device by replacing the relatively thick semiconductor substrate normally used in solar cells with a thin "wafer-bonded" substrate.

According to the team, the new device is considerably cheaper and lighter than conventional solar cells.

The photovoltaic characteristics of the new device also makes it better than those of conventional cells deposited on bulk substrates, as the wafers are just hundreds of nanometres thick, compared to the bulk substrates, which are several hundred microns thick.

During their experiments, Zahler and his co-workers found they could replace the regular, thick indium phosphide substrate with a very thin layer of the same material on top of a cheap, oxidized wafer of silicon – the wafer-bonded substrate.

They implanted an indium phosphide substrate with helium and heated it so that the expanding gas sheared off a micron-thin layer. Then they transferred this exfoliated layer onto the silicon wafer, before growing an indium gallium arsenide photovoltaic structure in the usual way.

"The transferred layer is just 900 nm thick," said team member Katsuaki Tanabe of Caltech.

According to him, this trick could reduce manufacturing costs by up to half, as they should be able to make hundreds of cells from the same amount of material currently used to make just one.

Tanabe said the cell also had a 20 percent higher electrical output, due to the high reflectivity at the interface between the indium phosphide and the silicon.

Moreover, the cell weighed only half as much as conventional device, he said.

The team is now planning to fabricate a solar cell containing four photovoltaic layers, which could have a high efficiency, surpassing cells containing two or three layers significantly.

"I find these results impressive," says Rolf Koenenkamp of Portland University in the US.

"The prospects for a four-junction solar cell seem much improved, where the exfoliation technique can indeed be applied reliably and at a reasonable cost,” New Scientist quoted him as saying.

The findings appear in the journal Applied Physical Letters. (ANI)