That’s quite easily explained. It was my subject at the university. My diploma thesis in 1997 was the first-ever realized plastic solar cell. My adviser was Niyazi Sariciftci, who had just come to Linz as a professor from the University California, Santa Barbara. I was his very first student. He was working on organic solar cells and so this became my thesis.

It’s an entirely new technology. Plastic solar cells are low weight, thin, bendable, and, most of all, you can produce them by just printing them out on a substrate. This provides a huge cost advantage compared with silicon solar cells, which are the state of the art.

My thesis was just a demonstration that this technology could be made to work. It was a proof of principle. Out of this thesis a company was founded called Quantum Solar Energy Linz (QSEL). I was the technical head of this company and our goal was to develop plastic solar cells that would be efficient enough to be commercially viable. When I did the proof of principle of the solar cell in 1997, the efficiency was far below 1 percent. The version we discussed in the 2001 Applied Physics Letters demonstrated an efficiency of 2.5 percent. A year later, we published another paper, revealing efficiencies of 3.5 percent.

It’s widely accepted that 5 percent is needed.

Well, it was a world record for plastic solar cells; it demonstrated huge improvement from the then state-of-the-art of around one percent. In effect, it was a significant point on the roadmap, suggesting that this technology is worth pursuing and will come to market within a very few years.

No. Not at all, because this was the first time anyone had ever shown that kind of efficiency for plastic solar cells.

We had to find a way to increase what’s called the "morphology" inside the photoactive matrix of the cell. The photoactive layer consists of two different materials, and what we managed to achieve at this time was a perfect mixing of the materials.

I’d say it was 50-50. Of course, it’s always hard work and you have to just keep going forward, step-by-step, but you also have to get lucky sometime—that’s when the harder steps just happen to work out. So sometimes it’s fortune, and sometimes it’s just hard work. By the end it’s a combination of both.

Well, a year later we published an efficiency of 3.5 percent in a paper that is also highly cited. I left the company and the field after that, so I didn’t stay in the field personally. I do know that the efficiency today is up to around 5 percent. Meanwhile the company that emerged from my thesis was acquired by Konarka at the end of 2002.

I founded and am CTO of my own company, Nanoident. Our goal is to produce printed semiconductor-based sensors—chemical, biological, biometric, and X-ray sensors.

They seem like they should, in principle, but in the details there’s a huge difference. The whole printing process is totally different; the materials are different. The closer you look, the more the technologies differ, and the more the challenges differ.

At the end of last year, we put our first products on the market and several more are coming out this year. The first was an optical multiplexer—an optical switch. The ones coming to the market this year are biochip sensors for medical analysis.

It’s a different application entirely and there’s no state of the art with which you have to compete. In solar cells, you’re always being compared with the relatively mature silicon technology. With silicon you get a lifetime of 25 years; you have 12 to 15 percent efficiency, and you have costs of about five Euros per watt peak. These are benchmarks—this is what you’re always being compared with. With plastic solar cells, you have 5 percent efficiency; you have a lifetime of at a most a few years. Now you have to be much, much cheaper than silicon to compete. This huge cost pressure is not achievable today. You can go to niche markets, but that’s all.

With these sensors you’re not compared to silicon. There are CMOS (complementary metal-oxide-semiconductor) cameras or chips, but they’re very high level and expensive. If you go into sensors, and you can get larger areas, larger pixel sizes, there’s no product out there today with which you’re competing. You’re going into absolutely new applications—like fingerprint scanners. You can establish new markets with new technologies, without having to always be compared to an existing technology. That’s a huge advantage compared to solar cells.

We also don’t have lifetime requirements. Biochip sensors are one-time use, or at most they only need a lifetime of one to three years. We don’t have an efficiency that we’re competing with. We just have to give the image, provide the result. In the very high-end consumer products, like CCD (charge-coupled device) cameras and CMOS devices, silicon will never be touched. But in all other areas, because of the characteristics of the materials with which we’re working—the low weight, bendability, the small spectral response, and the ability to print the sensor directly onto a substrate—we have huge advantages. So with plastic sensors, we’re not competing with silicon; we have new markets, new fields. The future is wide open.