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Prof. dr. Christophe Ballif: In the Air, on Sea and on Land: When Will Everything Become Solar?

Publish date: 24.05.2019



In this presentation, we will first review some the global current trends in the photovoltaics research and market. We will illustrate it with some of the research results and technology transfer realized by the teams working in Neuchâtel, Switzerland. This will include mainstream crystalline silicon with the emergence of so-called passivating contact structures. We’ll show recent progress in the field of front and back-contacted silicon heterojunction with device efficiency reaching 24 to 25% efficiency at lab-scale, as well the accompanying worldwide industrial developments. We’ll also show how interconnection technologies can be improved, from lab samples to high throughput production lines, reducing the costs of consumables, through the usage of multi-wires embedded in polymer foils.

In the second part, we’ll see how one can practically extend the learning curve of silicon, by considering multi-junction on silicon. In particular, the newest records obtained for III-V devices on Si (expensive) and perovskite cells on Si (potentially low cost) will be shown. With simple architecture of tandem Si/Pk devices, it is expected that such devices will soon come close to 30% efficiency. We’ll discuss shortly what it will take for this (or any technology) to catch up with the mainstream PV industry. 

The progresses in PV enable multiple new application of photovoltaics. In the final part, we’ll review some of the spectacular developments. We’ll scroll through some applications of PV for the IOT (energy scavengers), for mobility (airplanes, boats, …). We’ll end up with a special focus to development in the field of solar skins for roofs and façades, or so-called building integrated photovoltaics (BIPV). Switzerland, where citizens voted for an energy transition, has a leading position in this field, with spectacular example of building’s fully cladded with invisible (but still relatively efficient) modules. We’ll argue that “transformative approaches” in which c-Si cells are hidden behind front colors or even white filters, will enable a potential 40% market growth in the coming decade.


Prof. Christophe Ballif graduated as a physicist from the EPFL in 1994, where he also obtained in 1998 his Phd degree working on novel PV materials. He accomplished his postdoctoral research at NREL (Golden, US) on compound semiconductor solar cells (CIGS and CdTe). He worked then at the Fraunhofer ISE (Germany) on crystalline silicon photovoltaics (monocrystalline and multi-crystalline) until 2003 and then at the EMPA in Thun (CH) before becoming a full professor at the University of Neuchâtel IMT in 2004, taking over the chair of Prof. A. Shah.

Prof. Christophe Ballif is the director of the Phototovoltaics and Thin Film Electronics Laboratory (PV-Lab) at the institute of microengineering (IMT) in Neuchâtel (part of the EPFL since 2009). The PV-Lab has strongly contributed to technology transfer and industrialization of novel devices and full technology with numerous companies.

Since 2013, Prof. Ballif is also the director of the new CSEM PV-Center, also located in Neuchâtel. The CSEM PV-Center is focussing more on industrialisation and technology transfer in the field of solar energy, including solar electricity management and storage. At the core of the CSEM PV-center activities lies several "pilot lines" for various kinds of solar cells manufacturing, with a focus coating technologies, wet chemistry processes for crystalline silicon, metalisation techniques for solar cells, and a platform for developing "ideal packaging solutions and polymers" for PV modules. In addition, joined facitilites between CSEM and EPFL of over 800 m2 are available for modules manufacturing, measuring and accelerated aging.

Prof. Ballif was awarded with the Becquerel Prize in 2016. He is a member of Swiss Academy of Engineering Sciences (SATW) and a corresponding member of Slovenian Academy of Engineering.