Together with their project partners, scientists at the Photovoltaic Technology Evaluation Center PV-TEC at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg have succeeded in improving the traditional screen printing process for the fine-line metallization of silicon solar cells. Using specially developed fine-line screens, the project team was able to create contact fingers with a width of merely 19 µm and a height of 18 µm in a single printing step. This means that up to 30 percent less silver is needed, which in turn leads to a significant reduction in manufacturing costs.
Silicon solar cells rely on metal electrodes on their front and rear sides to carry the electrical energy generated in the semiconductor material from light irradiation. To this end, a flatbed screen printing process is typically used to print a fine contact grid onto the front side of the cell.
This grid should block as little as possible of the active cell surface from exposure to light and must be sufficiently conductive to keep the solar cells’ series resistance low. The technological challenge in the screen printing process lies in creating the narrowest possible continuous contact fingers with a sufficient height for good lateral conductivity.
Printing extremely fine contact fingers requires the use of highly engineered specialized screens and metallization pastes in addition to complete mastery of the screen printing metallization process.
“Working together with industry partners in fine-line screen printing metallization, in particular with screen manufacturers Koenen GmbH and Murakami Co. Ltd. as well as screen chemical supplier Kissel + Wolf GmbH, we have managed to reduce the contact fingers’ width to less than 20 micrometers — a reduction of 30 to 40 percent compared with the current industry standard,” explains Dr.-Ing. Andreas Lorenz, project manager in the Printing Technology group at Fraunhofer ISE.
Innovative fine-mesh screens were used in the metallization of passivated emitter and rear contact (PERC) solar cells in two independent test series. Using such a screen made it possible to create contact fingers with a width of merely 19 µm and a height of 18 µm in a single printing step. Not only are the contact fingers extremely narrow, their electrical properties are also outstanding.
When integrated into modules — particularly with newer technologies such as multi-busbar interconnection with 8 to 15 busbars — they enable a notable reduction of the power loss in the contact fingers. These newly developed screen printing processes require up to 30 percent less silver compared with the current industry standard with a contact finger width of approximately 30 µm.
As part of the experiment, PERC solar cells were metallized using the optimal screen parameters; a nominal finger width of 24 µm was selected due to the limitation with regard to the available number of busbars on the solar cell (in this case 5). The best PERC solar cell in this test series achieved an efficiency of h = 22.1%.
“Using highly engineered screen and paste systems for fine-line metallization, it could be possible to start manufacturing solar cells with nearly invisible contact fingers on an industrial scale in the near future. This would represent a great advantage for applications in integrated photovoltaics, where aesthetic, homogeneous module surfaces are in demand,” says Dr. Florian Clement, Head of the Production Technology — Structuring and Metallization Department at Fraunhofer ISE.
The results of these test series will be presented at two upcoming PV conferences — the 36th EU PVSEC in Marseille, France, and the 29th PVSEC in Xi’an, China.
The collaborative project “FINALE” (https://www.ise.fraunhofer.de/en/research-projects/finale.html), which focusses the development of fine-line screen printing processes and in which the researchers partly achieved these results, was funded by the German Federal Ministry for Economic Affairs and Energy BMWi and conducted in collaboration with industry partners Koenen GmbH, Kissel + Wolf GmbH and Wickon Hightech GmbH.
Further fine-line screen printing results which are presented here were realized within a cooperation between Murakami Co. Ltd. and Fraunhofer ISE.
Karin Schneider | Fraunhofer-Institut für Solare Energiesysteme ISE
Potential vaccine treats and prevents deadly streptococcal toxic shock
05.09.2019 | Griffith University
Research into Parkinson’s disease: binding-protein prevents fibril proliferation
03.09.2019 | Heinrich-Heine-Universität Düsseldorf
The demand for even higher resolution videos will continue to increase in the coming years. For this reason, the German public service broadcaster WDR and the Fraunhofer Heinrich Hertz Institute HHI will collaborate in the coming months to test the Video Coding possibilities offered by the next international standard VVC/H.266.
VVC/H.266 is the successor standard to HEVC/H.265. The latter is currently the most modern and efficient standard for Video Coding and is used, for example, in...
The recording of images of the human brain and its therapy in neurodegenerative diseases is still a major challenge in current medical research. The so-called blood-brain barrier, a kind of filter system of the body between the blood system and the central nervous system, constrains the supply of drugs or contrast media that would allow therapy and image acquisition. Scientists at the Max Planck Institute for Polymer Research (MPI-P) have now produced tiny diamonds, so-called "nanodiamonds", which could serve as a platform for both the therapy and diagnosis of brain diseases.
The blood-brain barrier is a physiological boundary layer that works highly selectively and thus protects the brain: On the one hand, pathogens or toxins are...
For the first time, a team led by Innsbruck physicist Ben Lanyon has sent a light particle entangled with matter over 50 km of optical fiber. This paves the way for the practical use of quantum networks and sets a milestone for a future quantum internet.
The quantum internet promises absolutely tap-proof communication and powerful distributed sensor networks for new science and technology. However, because...
Since their experimental discovery, magnetic skyrmions - tiny magnetic knots - have moved into the focus of research. Scientists from Hamburg and Kiel have now been able to show that individual magnetic skyrmions with a diameter of only a few nanometres can be stabilised in magnetic metal films even without an external magnetic field. They report on their discovery in the journal Nature Communications.
The existence of magnetic skyrmions as particle-like objects was predicted 30 years ago by theoretical physicists, but could only be proven experimentally in...
Theoretical physicists at Trinity College Dublin are among an international collaboration that has built the world's smallest engine - which, as a single calcium ion, is approximately ten billion times smaller than a car engine.
Work performed by Professor John Goold's QuSys group in Trinity's School of Physics describes the science behind this tiny motor.
04.09.2019 | Event News
29.08.2019 | Event News
16.08.2019 | Event News
06.09.2019 | Life Sciences
06.09.2019 | Physics and Astronomy
06.09.2019 | Physics and Astronomy