The latest Dual Line c-Si modular platform will be unveiled at the forthcoming SNEC 8th 2014, International Photovoltaic Power Generation Exhibition, being held in Shanghai, China May 20-22, 2014, at the Shanghai New International Expo Center. ROFIN-BAASEL Lasertech's booth is located in Hall 3, 615.
Success story Dual Line c-Si
Initially launched over three years ago, the Dual Line c-Si laser processing system has already been installed at multiple leading PV manufacturers facilities worldwide that are focused on PERC and selective emitter processes for improvements of up to a 1% absolute efficiency gain and higher productivity that lowers production costs.
‘Future Fab' project researching solutions for sub-surface damages
Key technical developments for PERC cells undertaken within the Photovoltaics Innovation Alliance FutureFab project, funded by the German Federal Ministry of Education and Research (BMBF), included in-depth analysis of short wavelength and short pulse laser tool requirements to minimize sub-surface damage during rear-side contact hole formation and optimize rear side passivation.
"The study revealed that complex ultra short femto and picosecond lasers create completely different surface structures after laser ablation of dielectric layers compared to nanosecond laser pulses", said Jens Theobald R&D Engineer at International Solar Energy Research Center Konstanz. "However, after the BSF [Back Surface Field] formation, studies showed that rear side passivation opening using green nanosecond laser pulses lead to the same level of high efficiency solar cells as it does with ultra violet picosecond pulses."
Important to the optimization of the process was the ability to use industrial lasers offering up to 5 times higher power compared to the previously used nanosecond laser source, reducing laser process cycle times per wafer significantly and improving overall wafer throughput, critical to volume production applications.
The Dual Line c-Si can now be equipped with a high power ns-SHG-laser with adapted beam profile specifically developed for the creation of larger dot diameters without increasing the laser induced damage. This patent pending process for a dot style opening of the passivation layers leads to scan-speeds exceeding 20 m/s. This is a significant breakthrough for PERC cells employing dot pattern designs, as laser ablation cycle times are reduced significantly and thus enabling lower production costs.
On the fly processing for elimination of handling and transfer times
The Dual Line c-Si system also features the inclusion of on the fly processing, a new system that virtually eliminates wafer handling and transfer times between laser processing cycles, improving productivity by providing processing speeds of up to 3,600WPH (Wafers-Per-Hour) ROFIN has recently received tool orders PERC cell processes for use in R&D development work as well as high-volume production line applications. The Dual Line c-Si has demonstrated > 20% for monocrystalline (mono-c-Si) and > 18% for multicrystalline (multi-c-Si) p-type cells could be achieved with the equipment, providing up to a 1% absolute efficiency gain.
Further developments are underway that are expected to lead to ‘on the fly' processing throughputs even beyond 4000 WPH.
