Affordable and efficient solar cells made by laser pulsing

Researchers at Purdue University in the US say their innovation may help to overcome two major obstacles that hinder widespread adoption of solar cells: the need to reduce manufacturing costs and increase the efficiency of converting sunlight into an electric current.

Critical to both are tiny microchannels needed to interconnect a series of solar panels into an array capable of generating useable amounts of power.

Conventional scribing methods, which create the channels mechanically with a stylus, are slow and expensive and produce imperfect channels, impeding solar cells’ performance.

‘Although laser scribing has been studied extensively, until now we haven’t been able to precisely control lasers to accurately create the microchannels to the exacting specifications required,’ said project lead Prof Yung Shin.

Research results have shown that the fast-pulsing laser accurately formed microchannels with precise depths and sharp boundaries. The laser pulses last only a matter of picoseconds, or quadrillionths of a second.

Because the pulses are so fleeting the laser does not cause heat damage to the thin film, removing material in precise patterns in a process called ‘cold ablation’.

‘This is very tricky because the laser must be precisely controlled so that it penetrates only one layer of the thin film at a time, and the layers are extremely thin. You can do that with this kind of laser because you have a very precise control of the depth, to about 10 to 20 nanometers,’ SHin said.

The researchers say their technology can be used in thin-film solar cells which are flexible, allowing them to be used as rooftop shingles and tiles, building facades, or the glazing for skylights.

Thin-film solar cells account for about 20 per cent of the photovoltaic market globally in terms of watts generated and are expected to account for 31 per cent by 2013.