Researchers at the University of Freiburg and the Fraunhofer ISE in Germany have built semi-transparent 14.5 x 14.5 cm organic photovoltaic modules with an efficiency of up to 9.26%, using a combination of industrially proven methods of slot-die coating and sputtering.

These methods are highly scalable to larger module areas.

The organic modules have an average transparency of 43.2%.

Experts working on semi-transparent organic photovoltaics usually have had to make a trade-off between light transmittance and the loss of efficiency associated with it, known as light utilization efficiency (LUE). In this case, the researchers achieved an LUE of up to 4% by using the 210.25 square-centimeter semi-transparent organic photovoltaic modules.

In each module, over 100 solar cells were interconnected using laser structuring.

Scaling up to larger areas is considered one of the major challenges in organic photovoltaics. “The fact that we have now, for the first time, successfully and with virtually no loss applied all the layers of the solar cells using the slot-die process is a breakthrough for us,” said Uli Würfel, head of the Organic and Perovskite Photovoltaics Department at Fraunhofer ISE.

Organic solar modules with light transmittance of more than 50% could replace window glass in building facades or greenhouses. The lower transparency can be an advantage in applications where tinted glass is desirable, such as façade elements and car roofs. Beyond wavelength-dependent transparency, organic modules offer advantages like flexibility and a low environmental footprint.

“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 mm. The next step is to achieve larger module areas here as well,” explains Mathias List, research associate for organic and perovskite photovoltaics at Fraunhofer ISE.

The research was part of the “Transparent PV – Development of Organic Solar Modules with High Visual Transparency” project, supported by Germany’s Federal Ministry for Economic Affairs and Climate. In August, the project findings were published in the journal ‘Joule’.

In May, researchers at Fraunhofer ISE claimed to have produced silicon heterojunction solar cells with a total silver consumption of 1.4 mg per watt of peak power. This consumption would be one-tenth compared to the current industrial production standard.

In January, Fraunhofer ISE launched the “PVgoesMV” project to demonstrate the world’s first medium-voltage solar projects using 3 kV string inverters, positioning the initiative as a response to rising raw material constraints and cost pressures facing the global solar industry. The project seeks to prove that operating a large-scale solar project at medium voltage is technically feasible and economically viable, as the global solar sector prepares for an estimated addition of around 73 TW of installed solar capacity by 2050.