MANUFACTURING
FEATURE
sector management micro for Trumpf. ‘And principally you use the laser beam, you guide it along these lines on the crystalline solar cell, melt the silicon and do the doping.’ The best lasers for this process are green lasers. This is because of the absorption of green light in silicon is very high compared to infrared. By carrying out this process Siebert expects that solar cell efficiency can be increased by 0.5 per cent, ‘maybe a little bit less’. Because of the selective capabilities of the laser the industry expects this laser process to also be used as an additional step to retrofit existing production lines, because it is just another process step with the doping machine. Trumpf’s product for this process is a 300W green pulse laser with a 300 nanosecond pulse duration. ‘It is fibre coupled and so this combination of high power and quite well suited pulse width makes this a perfect laser for this application,’ explained Siebert. ‘If you use fibre guiding you can use square shaped fibre with a 100micron etch length and then it makes spots in the region of 100microns or a little bit more.’
Siebert points out that while Trumpf is
a major laser machine maker it does not manufacture the type of machinery needed for solar cell production. ‘We are in sheet metal, but not in photovoltaics. As a laser manufacturer, for photovoltaics, we deliver the beam source, but we don’t do any machines. It’s important to say this.’ Trumpf has supplied a lot of beam sources for solar cell edge division. ‘Our major main application from the beginning has been to do edge division for photovoltaics. It is one of the most important applications for us and it was established at least two years ago,’ comments Siebert. Before lasers, solar cell manufacturers used sandblasting for edge division. In Siebert’s view the industry has made big steps to replace sandblasting with lasers for etch division. ‘No one establishing a new production line would choose sand blasting,’ he says with confidence. This is despite lasers being more expensive to buy. The reasons Siebert expects lasers to replace sandblasting machines is because the total ownership costs of lasers are less. ‘Sandblasting end users realise sandblasting has much higher costs of
Selective laser
doping is one approach for making solar cells more efficient
➤ PHOTOVOLTAICS 2012 17
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28