Tuesday, September 1, 2026
Scalable semitransparent organic PV modules could turn windows into power generators - Energy & Green Tech - Hi Tech & Innovation
As part of the "See-Through
PV" project, the research team also manufactured flexible, organic PV
modules on film. Credit: Fraunhofer ISE
Organic solar modules score points
for their flexibility, transparency, and a particularly good environmental
footprint. Wavelength-dependent transparency, in particular, is a major
strength of organic photovoltaics. Researchers at the University of Freiburg
and the Fraunhofer Institute for Solar Energy Systems ISE have now succeeded in
building 14.5 by 14.5- centimeter organic PV modules with an average
transparency of 43.2% and an efficiency of up to 9.26%. To achieve this, they
used a combination of sputtering and slot-die coating—both processes that are
industrially proven and highly scalable to large module areas.
"Scaling up to larger areas is
one of the major challenges in organic photovoltaics," explains Dr. Uli
Würfel, head of the Organic and Perovskite Photovoltaics Department at
Fraunhofer ISE. Good laboratory results with small, handmade solar cells often
cannot be transferred to industrial production because their manufacturing
process does not work over larger areas.
"The fact that we have now,
for the first time, successfully applied all the layers of the solar cells
using the slot-die process with virtually no loss is a major breakthrough for
us." The back electrodes of the solar cells are applied in the preceding
process step using sputtering, which is also an established manufacturing
method.
Balancing transparency and output
In the development of
semitransparent organic photovoltaics, there is always a trade-off between
light transmittance and the inevitable associated loss of efficiency, expressed
as light utilization
efficiency (LUE). With the 210.25-square-centimeter semitransparent organic photovoltaic
modules, the researchers achieved an efficiency of up to 9.26% with an average
visible-light transmittance of 43.2%. This corresponds to an LUE of up to 4.0%.
The project's results were published in the journal Joule in early
August.
"Now that we have the manufacturing process under control, we are optimistic that we can significantly increase transparency without compromising efficiency," adds Würfel.
Organic, semi-transparent photovoltaics
are particularly interesting for applications in building-integrated
photovoltaics and agrivoltaics. Credit: Fraunhofer-Institut für Solare
Energiesysteme ISE
From glass facades to flexible film
Organic solar modules with light
transmittance well over 50% could be used in place of window glass in building
facades or greenhouses. In contexts where tinted glass is desirable—for
example, in car roofs and facade elements—lower transparency can even be an
advantage.
In each module, more than 100 solar
cells were interconnected using laser structuring. The solar cells consist of a
back electrode that reflects near-infrared light, deposited onto a glass
substrate via sputtering; an absorber layer made of organic semiconductors; and
a metal-free top electrode made of the polymer PEDOT:PSS, applied in multiple
layers using a slot die. Heraeus Epurio developed a new PEDOT:PSS formulation
for this top electrode, which helped the PV modules achieve higher
transparency.
Slot-die coating is compatible with roll-to-roll processes and is therefore also suitable for producing solar modules on film. "As part of the project, we have already produced the first flexible, organic PV modules that retain 100% of their original efficiency after 1,274 bending cycles over a rod with a diameter of 15 millimeters (0.6 inches)," explains Dr. Mathias List, research associate for organic and perovskite photovoltaics at Fraunhofer ISE. The company ROWO Coating manufactured the films for this purpose. "The next step is to achieve larger module areas here as well."
Provided by
Fraunhofer-Institut für Solare Energiesysteme ISE
by Claudia Hanisch, Fraunhofer-Institut für
Solare Energiesysteme ISE
edited by Lisa Lock, reviewed by Robert Egan
Source: Scalable semitransparent organic PV modules could turn windows into power generators










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