How and when was 3Sun established and why the choice of Catania?

3Sun was established in 2010 as a joint venture between Enel Green Power, which was looking to introduce photovoltaic panel production to Europe, STMicroelectronics and Sharp Solar. Catania was chosen as the location because STMicroelectronics already owned a site here. Initially we produced about 200 megawatts a year, or 4,000 thin-film solar panels, with a 10% efficiency rate. Today, however, the modules feature an efficiency of up to 24%. Until 2017 we produced almost 7 million modules, all for Enel Green Power, installed in various solar fields. Over time this technology was becoming obsolete due to the spread of crystalline silicon-based technology.

What difference is there between the old thin-film and new crystalline-silicon-based technology? How did you approach this change? And what results have you had?

With thin film, you took a substrate, which could be glass or metal, and apply a thin layer of silicon or other materials, with the advantage that it can be applied on all surfaces but the drawback of having low efficiency. The new technology involves assembling many small rectangular "bricks" of monocrystalline silicon (called "wafers") obtaining high crystal purity. We then perform a series of processes by applying functional active layers only a few nanometers thick, increasing conversion efficiency from solar energy to electricity.

Photovoltaic technology is constantly evolving. Which was the next step?

In 2015, following the exit of STMicroelectronics and Sharp, Enel increased its competitive edge by combining expertise on silicon and semiconductors used in microelectronics and starting to produce bifacial modules, so that they can absorb light from the back as well, the diffuse light or light reflected from the ground.

Then, in 2018, 3Sun developed the first bifacial heterojunction (HJT) panel. You were the first in the world to develop this technology, which is therefore 100% Italian and European. What is it all about and what advantages does it offer?

By combining crystalline silicon with amorphous silicon layers (heterojunction), we can maximize the ability to extract energy from sunlight, resulting in more efficient and competitive modules. This technology differs from previous technologies because the cell has an almost perfectly symmetrical architecture. We can therefore achieve a 95% bifaciality factor, while other technologies, not being symmetrical, can reach no more than 70 to 80%. Thanks to this technology, in 2020 3Sun set the world record for commercial cell efficiency, reaching 24.63%.

Besides greater efficiency, heterojunction also has the advantage of greater sustainability. Why?

To create a solar cell, I need to create a diode, introducing a few atoms other than silicon inside the silicon. Traditional technologies use a high-temperature (diffusion) processes, adding boron or phosphorus at 800°. In heterojunction we make this diode by depositing a thin layer of silicon that already contains boron or phosphorus atoms, with temperatures below 200°. Our modules, entirely manufactured in Italy, use neither lead nor fluorine and maintain 91.8% performance after 30 years.

After producing exclusively for Enel, you are now ready to enter the market. With what products?

Today, production is divided between bifacial modules designed for large energy production plants and single-sided modules for installing on the roofs of homes. Our 3Sun B60 is a bifacial module designed for large solar installations or commercial and industrial applications involving large areas, in a 2.172 x 1.303-meter format, with a power output of up to 680W and 24 percent designed for installation on buildings, have a size of 1.754 x 1.096 meters and a maximum power output of 480W, with an efficiency rate of 25%.

Have you calculated the reduction in carbon dioxide emissions for each module?

Of course, studies also confirmed by leading research institutes, such as Fraunhofer, tell us that 1KW/h produced from coal is equivalent to 1kg of CO2, 1kW/h produced with natural gas is 500 grams, and a traditional photovoltaic module is 50 grams. Our heterojunction modules produce less than 40 grams of CO2 per kW/h.

3Sun plays a key role in the European decarbonization process. Thanks to an agreement between Enel Green Power and the European Commission you have received sufficient funding to significantly increase production. What is the Giga Factory?

The development of TANGO (iTaliAN pv Giga factOry) will represent a real revolution in both our organization and output. From the annual production of 200MW achieved in the past years, we will grow to about 3GW in 2025. Ours will be the largest photovoltaic production plant in Europe, capable of operating on a continuous cycle, 24 hours a day, 365 days a year. When fully operational, the Giga Factory will produce 14,000 PV panels and 800,000 solar cells per day.

A European product, intended for the European market, is also of strategic geopolitical importance.

Yes, the goal is to produce a strong European product capable of competing with Asian products and absolutely competitive in terms of performance. And we can achieve this also thanks to a European regulatory framework that is naturally respectful of workers' conditions, sustainability of production processes and traceability of materials. For the first time, product quality has been identified as a rewarding parameter, an important step in enabling a true European PV supply chain. Another important goal is to create an independent European value chain that can better cope with changes in global geopolitical scenarios and changes in raw material prices.

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