Applied to various types of solar cell
The researchers studied the effect of the nanostructures in various types of solar cell. They investigated both the previously stated crystalline silicon solar cells and the far thinner so-called thin-film solar cells. ‘Roughly ninety percent of the current market consists of crystalline silicon solar cells. Those are the mostly dark blue or black panels that you see everywhere on roofs. There are also thin-film solar cells in which thin layers of deposited semiconductor material form the photoactive layer. In both types of solar cell the application of photonic nanostructures resulted in a yield that was the same or even higher but with less material. That could ultimately be advantageous for the cost price of the solar cells,’ explains Lenzmann.
Subsequent steps and challenges
For both types of solar cell the application of nanostructures was therefore found to be advantageous. A suitable production technique for nanostructures is already on the horizon. Marc Verschuuren from SCIL Nanoimprint Solutions (a venture start-up within Philips) is developing a new technology to be able to make nanopatterns quickly, cheaply and reproducibly with the help of a stamping technique.
Cheaper, faster and less demanding
‘Our technology is cheaper than existing lithography techniques, considerably quicker than writing patterns with an electron beam, and we can attach nanostructures to kilometres of surface,’ says Verschuuren. ‘Now we can stamp structures with dimensions of 10 nanometres which is more than adequate for application in solar cells. Furthermore, for our stamps it does not matter if the surface to be written on is contaminated, which means we can work at room temperature and under atmospheric pressure.’
Towards large-volume production
If solar cells become increasingly thinner they will also break sooner. That is not a problem as far as Verschuuren is concerned: ‘Our stamping technique is very subtle and we do not need to exert any large forces. That is unique for a contact technique like this.’ SCIL Nanoimprint Solutions is currently working on making its nano-imprinting technique suitable for large-volume production. ‘This collaboration with ECN and AMOLF is a good way of showing the possibilities of our technology to potential clients,’ says Verschuuren. Once the NanoNextNL project has been completed the three parties will therefore work together on a follow-up.
The economic feasibility of the project results is now being investigated, says Lenzmann. ‘In the solar panel market price is a crucial competitive factor. For the use of photonic structures, changes in the production process are needed. Manufacturers must also purchase additional equipment. Now we will first of all carefully analyse when that would be worthwhile.’
A benchmarking study: Plasmonic light-trapping in a-Si:H solar cells by front-side Ag nanoparticle arrays
Article Imprintlithografie stempelt nanostructuren in grote oppervlakken (source: Mechatronica & Machinebouw)