Portrait of Christophe Ballif


Christophe Ballif photovoltaics neuchâtel

Lives in Neuchâtel

Native of the Vallée de Joux

Born in 1969

Fan of skiing

Professor, EPFL – Photovoltaics and Thin-Film Electronics Laboratory (PV-LAB)

Director of the CSEM Photovoltaics Centre (PV-Centre)


The sun gives us energy equivalent of 150 litres of petrol per m2 per year. In 2019, photovoltaic energy became the cheapest source of electricity in sunny countries. In Germany, for example, large solar parks (approximately 100 megawatts) produce electricity at 3.8 euro cents per kW at the lowest price and at an average price of 4.6 euro cents. By way of comparison, the latest gas or nuclear plants are 50 to 300% more expensive. 

In Switzerland, and in Neuchâtel in particular, support programmes such as the single payment scheme at federal level and the support programme from Neuchâtel city council enable citizens to invest in photovoltaic technologies. Furthermore, Viteos buys back the energy produced at an acceptable rate, which is not the case with all Swiss electrical companies.


Christophe Ballif

Passionately interested in science and environmental issues, Christophe Ballif divides his time between the EPFL laboratory, where he heads the research team in Neuchâtel, teaching in Lausanne and at the CSEM, with activities dedicated to industrialisation.  We interviewed this researcher with a resolutely sunny disposition.

How did the centre for expertise in the field of photovoltaics emerge in Neuchâtel?

It came about thanks to developments in the regional and international context.

Traditionally, research related to photovoltaics was conducted at the University of Neuchâtel’s microtechnology institute. In 2009, this became part of the EPFL, at a time when the demand for renewable solar energies was growing exponentially. The laboratory was undertaking lots of industrial projects, whereas the EPFL normally concentrates more on fundamental research. Quite naturally, the idea emerged of performing some of the activities at the CSEM, whose core business is in the area of technology transfer.

At international level, the Fukushima disaster facilitated the development of the centre of excellence in photovoltaics at Neuchâtel, with Switzerland deciding to forgo nuclear power and to renew investments. This enabled the emergence of a new research structure at the CSEM: the PV-Centre. It was launched in 2013, with 19 million euros of financial support from the Swiss state for the first four years, which was then renewed.  

In total, around one hundred people currently work in the area of photovoltaics and more generally on energy systems at the EPFL and the CSEM in Neuchâtel, with many different companies linked to these teams.

Who are your clients?

The CSEM PV-Centre has contracts with around forty companies. Many of them are in Switzerland, including the canton of Neuchâtel. We also have clients in Europe, the USA, and even in Asia. But, in the first instance, we seek to work with Swiss industry, since the CSEM’s mission is to be a national driver of innovation. However, it is of course essential to be connected to the wider world, in order to understand what is happening there and to remain competitive in the clean energy race. From Neuchâtel, we have contacts with all the major manufacturers of solar panels worldwide - contracts, non-disclosure agreements, exchanges of samples, specific technical developments. 

What recent projects have you worked on with industrial partners in Neuchâtel?

Recently, we developed a new way of manufacturing very high yield solar cells, using a technology known as polycrystalline silicon heterojunction: crystalline silicon (one of the family of semiconductors) is coated with layers of amorphous silicon (a few dozen nanometres). In collaboration with the Meyer Burger group and its R&D centre in Neuchâtel, we have established low-cost industrial-purpose processes. We have also done lots of work with the group on interconnection technologies, i.e. how solar cells are assembled between each other. For example, we have successfully reduced the cost involved in connecting them by a factor of five. Around a gigawatt (the peak power of a large nuclear plant) of these technologies has been ordered by the Meyer Burger group; a real achievement.

We are also working on new ways to produce solar cells, with a new type of plasma reactor, with Indeotec SA, a start-up previously incubated at Microcity (ex-Neode), which can greatly simplify the production of high yield thin layers useful in other industries. And of course we are working with Solaxess, a CSEM technology start-up, on architectural solutions. We are also contributing to the development of new-generation solar simulators with the company Pasan SA, based in Neuchâtel, which is part of the Meyer Burger group. We naturally have close links with Blue Birds Photovoltaics, which makes specialist PV products. And of course we have links with many companies in the region, for applications such as watchmaking or surface coatings, for example through our expertise in colours right through to “absolute” black, or for our solar cells built into watch straps or dials.

What are your main areas of research?

I would mention seven.

  1. New procedures for crystalline silicon, to make the panels even more efficient and cheaper to manufacture. We have a wide range of technologies and patents that we are constantly expanding, and numerous national and international collaborations. One of our specialities is the production of near-perfect electrical contacts using silicon, known as passivating contacts.
  2. The development of special products for construction and architecture: white solar panels were invented at the CSEM. They are now marketed by Solaxess, who have won lots of awards. With Issol Suisse, a subsidiary of the Belgian parent company, we have developed slate-coloured solar panels. A prize was awarded for the best solar farm in Ecuvillens. This innovation made the cover of the prestigious Nature Energy review, demonstrating a change in attitudes, with increased emphasis on applications.

© EPFL 2019
  1. Product reliability: panels will remain on a roof for around forty years, so the longevity of their electrical functions is vital. They are tested for changes in temperature, humidity, pressure or hail impact. We have a unique platform at Neuchâtel for manufacturing high-quality polymer encapsulation film, for making modules and testing them in an accelerated manner. An EPFL doctoral student, in collaboration with the CSEM, has invented solar panels which are unbreakable and reliable. They are not made of glass and are light, which also makes them easier to install.
  2. Special products for mobility: we are developing made-to-measure panels for stratospheric missions (SolarStratos for example), which are light, highly efficient, and can withstand temperature cycles of – 60 to + 120 degrees. We are also producing solutions for the sailing and automotive sectors.

  3. Energy harvesters: these are very small solar cells which can be integrated just about anywhere and work very well with little light. They are fitted, for example, in watch dials or control boxes, as an auxiliary energy source. By adding a sensor and communication capabilities to them, these energy harvesters are becoming key elements in the IoT (Internet of Things) architecture we are developing in synergy with various companies and of course within the CSEM, alongside aspects of miniaturisation, systems integration and low consumption. 

  4. Future technologies: perovskite cells combined with silicon or other materials would make it possible, for example, to significantly improve yields, by up to 35 or even 40%. Perovskite/silicon cells are a highly topical issue. However, there is still a lot of work to be done on the resistance of materials over time with these types of cells.

  5. The integration of photovoltaics into energy systems: producing solar energy is good; optimising its use is even better. We will need to be able, for example, to store solar energy, to better quantify the charge level of batteries, and to improve their use and their cost. It is already possible for us to simulate electricity networks in order to understand the potential penetration of photovoltaics in certain areas of towns. It is also possible to simulate complex energy systems, for a house, a district, or even a city, and going as far as to include the conversion of surplus electricity into gas (power-to-gas). In-depth analysis and predictive maintenance are made possible thanks to Big Data techniques. This is a truly vast field.

In your opinion, what are the challenges for photovoltaics in the coming years?

First of all, there is the challenge of the market, which is macropolitical and external to the technology itself. Without development of the latter, the very existence of humanity as we know it is called into question. States must apply the Paris Agreement and assume their responsibilities, by introducing appropriate policies for the decarbonisation of our energy system. Photovoltaics will be the number-one solution for contributing to this decarbonisation, no matter what you think of this energy source, because its long-term potential in terms of use and costs is unbeatable. On the other hand, if the photovoltaics market, which is just getting started, stagnates through a lack of progressive policies or due to the work of the many lobbyists opposed to any change, then the industry developing it will struggle to grow.  

Then there is Chinese competition, with issues related to intellectual property and direct or indirect subsidies, which it is hard to fight against, even if you are at the cutting edge of innovation. But the Chinese also have the courage to invest massively, to be efficient in terms of production, and to establish an internal market for solar technology.

Concerning the technology, we are in a process of continuous innovation. Recently, for the first time in a laboratory, we achieved a 25% yield with silicon cells which are relatively simple to produce. Although silicon cells are already cheap now, they will need to be even cheaper tomorrow, and above all more efficient. This will be the simplest way of bringing down solar electricity costs (more kWh per m2). For all photovoltaic systems, the cheaper solar electricity becomes, the more the financial margin for managing energy systems increases!

Reliability is also central to our concerns, for all the technologies we are developing. For some time, perovskite cells have been the central focus, due to their very high efficiency. On the other hand, most perovskite systems typically lose 10% of their yield per year, which is unacceptable (but nonetheless represents major progress compared to five years ago). By way of comparison, crystalline panels conserve 85% of their nominal yield after 25 years. As such, there is still a lot of work to be done to ensure that perovskite cells can be marketed and used for many years.

Finally, there has been significant challenge in the built environment. Attitudes in the architecture and construction sector have to move forward. After all, for the last five years or so, it has been possible to have elegant roofs or facades using the newly developed panels, thanks in part to all the new colouring solutions. I hope that very soon it will be unimaginable to renovate a building without including photovoltaics. The roof of tomorrow should even be entirely solar. It’s affordable, it can be done right now, it’s attractive, and it provides an initial response to a global problem.

What do you think of Neuchâtel’s innovative ecosystem?

Neuchâtel is an extraordinary canton. I appreciate both the industrial and microtechnology ecosystem. Here, people think towards concrete objectives, they have precision in the blood. There is a marked spirit of entrepreneurship. This is supported by excellent institutions such as the CSEM, the HE-Arc, the University, and the EPFL.

But we must remain alert and invest to preserve this dynamic. One thing that is missing is venture capital. Financial support amounting to hundreds of thousands of francs makes it difficult for innovation to take quantum leaps. At institutional level, abroad, new research programmes are often supported to the tune of hundreds of millions, if not billions, in additional funding, in fields such as energy, advanced manufacturing or digitalisation. Switzerland is often overly cautious. This is a shame, since the quality of training, the staff you can recruit, and life in general are unbeatable in Switzerland and in Neuchâtel!

Victoria Barras