I received my Masters degree in Organic Chemistry (with Prof. H. Wijnberg; Univ. of Groningen) with a minor in Logic and Philosophy of Science in 1979, and in 1985, my cum laude Doctorate (also with Prof. H. Wijnberg), where the title of my thesis was, "Inherently Chemiluminescent Compounds as New Labels in Clinical Analysis" (ISBN 90-9000836-5). From 1984-1989, I was the Project leader of the "Thermochemiluminscence Project" at the University of Groningen, and from 1987-1989, I was a Member of the Scientific Committee of the Symposia on Quantitative Luminescence Spectrometry in Biomedical Sciences, Gent.

“We are convinced that fullerene derivatives will continue to play an important role in organic and polymer electronics.” Photo: © Michel de Groot

In 1988, I became a visiting and consulting scientist at Quest Systems Inc. (Bedford, Mass., USA), and from 1990-1992, I was a Senior Research Chemist with Syncom B.V. (Groningen). After I worked on the development and commercial application of a new large scale separation and purification method for the fullerenes C60 and C70 in 1991-1992, I became a visiting postdoctoral scientist with Prof. F. Wudl, Institute for Polymers and Organic Solids, University of California, Santa Barbara. From 1993-1995, I worked with Prof. Wudl on the synthesis and characterization of C60 derivatives and heterofullerenes, and the application in blends with polymers for NLO, optical limiting, ‘plastic’ PV cells, photodiodes.

From 1995-1996, I was a visiting scientist with Prof. Dr. E.W. Meijer, TUE, where we worked on optical resolution of chiral fullerene derivatives, ES-MS characterization of dendrimers, and computer simulation of dendrimer ES-MS spectra. From 1996-2002, I was the project leader of the Dutch Plastic PV Solar Cells Project (Materials Science Center, University of Groningen). Projects such as these are funded on a yearly basis by the Netherlands’ Agency of Energy and the Environment, Utrecht, in collaboration with Eindhoven Technical University.

I was project leader of the E.E.T. Polymer PV Project (Univ. Groningen, Eindhoven Technical university, Energy research Centre of The Netherlands, and Philips Research) for Phase I of Project period, 1/12/1998-1/12/2003. I was also a participant in the European Community’s Joule III research project "Molecular Plastic Solar Cells" (JOR3CT980206) from 1998-2000.

In January 1998, I became a Universitair Hoofddocent at the University of Groningen, and in 2000, I became a full professor in Chemistry (Chemistry of (Bio)Molecular Materials) there. I also served as the Director of chemistry education at the University of Groningen from 2004-2005. In 2005, I became the CSO of Solenne BV in Groningen.

So, my (organic) chemistry education was through Prof. Hans Wynberg and, after some asymmetric catalysis work (M.Sc.), my early research (Ph.D.) was on chemiluminescence and its application in immunoassays.

Early 1991, in Groningen, right after the publication by Krätchmer and Huffman, I developed a (relatively) large-scale method for the preparation of (ultra)pure C₆₀. This marked the start of a turning point in my scientific career, because this led me to my post-doc period with Prof. Fred Wudl at UCSB from 1993 to 1995. He taught me fullerene chemistry, and he introduced me to the field of organic electronics.

In 1992, Sariciftci and Heeger discovered the photoinduced electron transfer between certain conjugated polymers and C₆₀. My collaboration with the Heeger group (within the Institute for Polymers and Organic Solids [IPOS] with Wudl) started right after I made a very soluble fullerene derivative (PCBM). I gave this to them when I heard about their research and about their solubility problems, as a replacement for the very insoluble C₆₀ in blends with conjugated polymers. This was an extraordinary success.

It led to a series of joint publications, among which was one on the first bulk-heterojunction solar cell, made with conjugated polymer MEH-PPV and PCBM (Yu G, et al., Science 270, 1789-91, 1995). This paper marks the birth of the "plastic solar cell" in its modern form.

Soon after I returned to The Netherlands, I decided to go full power on "plastic" PV research. At that point, Sariciftci (in Linz, Austria) and I were among the very few researchers working on the subject and we decided to make it a joint effort to develop the field.

This was the first review article on the subject, and it was written by the experts in the field, not by an outsider. It is quite easy to read and it summarizes most of the issues, as they were known at that time. Although by now, the content starts to become more and more outdated—the field has grown dramatically since then—for most researchers that were new in the field, this paper has always been a convenient starting point for earlier references.

The article contains a brief historical section; it describes the background physics on polymer:fullerene donor-acceptor combinations, the principle and some of the physics of the bulk-heterojunction, some of the issues with respect to morphology of the active layer, as well as some of the approaches to increase the efficiency of this type of photovoltaic devices.

We have continued the plastic solar cell research ever since. Intense collaboration with mainly René Janssen (Technical University of Eindhoven), Christoph Brabec, Serdar Sariciftci, and a little more recently with Paul Blom (Zernike Institute for Advanced Materials, University of Groningen) has been great, very interesting, and quite prosperous. At the moment, various collaborations are ongoing within several frameworks of funding. In parallel, we are working on other projects in which fullerene derivatives play an important role (like FETs and holographic imaging). Apart from our fullerene research, we work on p -conjugated systems in general, both in truly fundamental and in application-directed projects.

We are convinced that fullerene derivatives will continue to play an important role in organic and polymer electronics. Since 2005, the Groningen University spin-off company Solenne BV provides the R&D community worldwide with fullerene-based n-type semiconductors.

From what we hear, we are quite optimistic that the first plastic solar cells will be on the market within the next five years in some form. The field is growing rapidly, the number of research groups in the field is growing fast. Industrial interest, start-ups, increasingly interested venture capitalists and other financial institutions—it’s happening! The plastic solar cell efficiency may be up to 6%, according to the latest report from UCSB, and we are optimistic that efficiencies of 8-11% can be reached within the next 5-10 years. It would be a dream come true!