Solar cells: improving the print process

Paul Boughton

DEK Solar, a provider of screen printing equipment and processes for fuel cell and solar cell manufacture, has announced the result of metallisation tests that show the possibility for significant cost savings and process improvements in the print process.
DEK has published a paper, Fine Line Printing of Front Side Metallisations Using Ultra Fine Mesh and Stencil Technologies. It was developed in collaboration with DuPont Microcircuit Materials (MCM), a manufacturer of high efficiency photovoltaic metallisation pastes. The two companies evaluated ultra-fine wire mesh screens and metal stencils in both single and dual printing processes in order to investigate whether it was possible to improve cost per watt through increasing cell efficiency and reducing paste consumption.
Key findings were:

* Use of ultra-fine meshes in single print mode can enable reductions in paste consumption up to 30 per cent without effecting cell efficiency. In this mode the busbar thickness is significantly reduced causing a reduction in solder adhesion forces

* In dual print mode the use of a stencil to print the fingers and a 400 mesh to print a dedicated busbar paste can achieve total laydown reductions up to 40 per cent and a relative increase in efficiency >0.5 per cent. Use of dedicated busbar paste enables high solder adhesion forces to be maintained.
Tom Falcon, Senior Process Development Specialist at DEK Solar, said: “We’re really excited by the results of these tests, and the potential impact this might have on solar cell production in the future. By showing that significant cost savings can be achieved by reducing silver usage, whilst also generating improvements in both electrical efficiency and reliability, we feel that both solar cell manufacturers and consumers will benefit.
DEK and DuPont MCM carried out these tests over a period of six months at the DuPont MCM facility in Bristol, UK.
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