The world-renowned Fraunhofer Institute for Solar Energy Systems (ISE) has
continued progress in producing high-efficiency solar cells using Aerosol Jet
printing equipment developed by Optomec.
ISE's most recent results were presented on October 1, 2008, at the Crystal
Clear "Workshop on Metallization for Crystalline Silicon Solar Cells" held in
Ultrecht, The Netherlands. The Aerosol Jet printed solar cells achieved efficiencies
of over 20% when combined with Light Induced Plating (LIP) and Annealing, versus
an average efficiency for screen-printed mono-crystalline front junction silicon
solar cells in the range of 16–18%. The narrower, higher integrity collector
lines produced by Aerosol Jet deposition systems have higher conductivity and
a lower shadowing effect, thereby increasing cell efficiency. In addition, because
the process is non-contact, Optomec's Aerosol Jet system can print on thinner
wafers and with less breakage than screen printing.
The Fraunhofer study states, "So far, the front side metallization holds
the main potential for a further increase in cell efficiency. The main targets
are the reduction of the metallized area to reduce shading losses, a low contact
resistivity to a lowly doped emitter, and a high line conductivity to transport
the current as loss-free as possible out of the cell.
"The cells fabricated in this work combine the advantages of a new advanced
front side metallization with an already established rear contact process, which
are both industrially feasible. The front side grid was aerosol jet printed
and light induced plated achieving line widths below 45 micron. On solar cells
with an 110V/sq emitter record cell efficiencies of 20.3% were measured. In
fact in a recent work, Fraunhofer ISE has found that the optical width of an
aerosol jet printed and plated contact embedded in a module is only 43% of its
geometrical width further reducing fill factor and providing increased cell/module
The study goes on to highlight that the shape of these collector lines helps
to promote the reflection of light back onto the solar cell: "In fact
in a recent work, we have found that the optical width of an aerosol [jet]-printed
and plated contact embedded in a module is only 43% of its geometrical width."
For volume production applications, Optomec has developed a high-throughput
40-nozzle Aerosol Jet deposition head that prints a solar cell every 2.5 to
3 seconds. Additionally, the non-contact nature of the Aerosol Jet system enables
high-yield printing on thinner photovoltaic wafers.
Optomec is the world-leading provider of additive manufacturing systems for
high-performance applications in the Electronics, Biomedical, and Aerospace
& Defense markets. These systems utilize Optomec's proprietary Aerosol
Jet technology and LENS® powder-metal fabrication technology. The company
has a global customer base of industry-leading manufacturers.
LENS is a registered trademark of Sandia Corporation.
Aerosol Jet is a registered trademark of Optomec, Inc.