Featured Scientist from
Essential Science IndicatorsSM
In February 2009, Essential Science Indicators
Reuters welcomed Dr. Nir Tessler to the
top 1% in the
field of Chemistry. Prior to this, his work has also
appeared in the top 1% in the field of Materials
Science. His overall record in our databases includes
66 papers cited a total of 3,021 times between January
1, 1998 and December 31, 2008.
Dr. Tessler is a Professor in the Electrical
Engineering Department of The Technion – Israel
Institute of Technology in Haifa, Israel.
In this interview, he talks with
ScienceWatch.com about his highly cited work.
Would you tell us a bit about your educational
background and research experiences?
I received a B.Sc. summa cum laude from the Electrical Engineering
department, The Technion - Israel Institute of Technology in 1989. I then
continued towards an M.Sc., studying semiconductor optical amplifiers and
their nonlinear response. This was followed by research that went deeper
into semiconductor device physics, and in 1995 I submitted my D.Sc.
dissertation on charge carrier dynamics in quantum well lasers and the
implications for ultrafast III-V lasers. Towards the end of my Ph.D., I
decided that I wanted to change fields of research, and my main preference
At the time, it was too early for biologists to appreciate the potential
contribution of electrical engineers and I could only go midway, and
applied to groups in organic electronics. With the generous help of the
Rothschild Fellowship I joined the group of
Professor Sir Richard Friend at the Cavendish
Laboratory at the University of Cambridge. It was at Cavendish where I
learned what one means by polymer, let alone by organic polymer. Looking
back, I think that the foundations of my knowledge and research attitude
towards organic semiconductors were laid during my first two years at
for local network.
Today, I have an active research group at the Nanoelectronic Center, which
is part of the Electrical Engineering department at The Technion. The
topics largely deal with the use and understanding of semiconducting
molecules. Although most people know my name as the one who made the first
optically pumped polymer laser this is probably the only application that
is not directly pursued in my lab. I also get the opportunity to glance
towards biology through collaboration with colleagues on "conjugated
peptides" and on "alternative energy sources using field-grown plants."
What would you say is the main focus of your work, and
what about this area drew your interest?
My main focus is on making new device architectures, developing new
materials, and understanding the device chemical-physics behind it all. I
would say that I was drawn because I found it exciting, and so far, it is
Your most-cited paper is the 1998 Science
article, "Integrated optoelectronic devices based on conjugated
polymers." Would you talk about this paper, its goals, findings, and
significance for the field?
This work took place while I was at Cavendish, and it was roughly when I
was becoming a member of staff through an Engineering and Physical Sciences
Research Council advanced fellowship. As I recall, I was working with my
two hands in the glove box when a post-doc there at the time I didn’t
know too well said something like "Wow, I have never seen a transistor as
good as the one I just made." My immediate reaction was to challenge him
and say, "If it is so good then it should be able to turn the light on in
the LED I am making." As some of your readers know, my colleague is now a
professor at Cavendish (Professor Henning Sirringhaus). What I am trying to
say is that there were no "plans," "goals," or "strategy," but it was
rather two guys having fun at the lab.
Of course after that we finished "playing" and showed the result to
Professor Friend, and we had several discussions where we came to realize
the huge scientific and commercial potential impact of this work. It was
the first report of an all-organic smart-pixel, which is the basic
structure behind display screens. It also showed that it is possible to
integrate (in a beneficial manner) different organic devices and thus
create a higher hierarchy.
I believe that this work made an impact because it ignited the imagination
of many who decided to devote more of their effort towards this topic. In
the commercial world, this work and its accompanying patent started the
effort towards the establishment of the company known today as Plastic
Logic. The creation of this company and others around the world is serving
as a positive feedback to the scientific community thus pushing this field
Before concluding I should also mention that at the same time a very
similar work was being carried out at Bell Labs and the paper by
Ananth Dodabalapur was published shortly after ours.
One of your more recent papers is from Nano
Letters, "Tuning energetic levels in nanocrystal quantum dots
through surface manipulations." Would you tell our readers a little
bit about this paper?
"My main focus is on making new
device architectures, developing new
materials, and understanding the device
chemical-physics behind it
In our group we have been working on extending the functionality of
polymer-based devices from the visible to the NIR part of the spectrum by
adding nanocrystals to the semiconducting polymer matrix. One of the
obstacles was that the energy level alignment between conjugated polymers
and nanocrystals of choice was not always favorable for the application we
sought (LEDs require type I and solar cells require type II alignment). As
we are electrical engineers it is most important for us to control the
properties of the building blocks being used to make advanced devices. In
standard devices the tuning of energy level alignment of two materials is
one of the existing tools.
We tried to find a solution to that by applying the well-known effect of
energy level tuning through the assembly of dipole-carrying molecules onto
surfaces. As it turned out, we were rather naïve expecting that
molecules on the surface of a 5nm diameter nanocrystal would create an
effect identical to molecules on flat (2D) surfaces.
As the paper shows, we were able to demonstrate that through the choice of
specific ligands (molecules) it is possible to tune the position of the
nanocrystal’s energy levels. However, we still can’t explain
what the exact mechanism behind it is and we are definitely far from
understanding why the effect is different between 2nm and 5nm diameter
nanocrystals. This work was a success mainly due to an excellent Ph.D.
student in my group, Michal Soreni-Harari.
What are the potential applications that might stem from
I hope that one day we will see real fully integrated all-plastic
optoelectronic devices. The work around the world shows that one can print
batteries, print transistors, print solar cells, print displays, print RF
transceivers…if we know how to functionally integrate them all, we
will have smart applications that could be designed on the PC and printed
out right away with close to zero development cycle. When this happens,
consumer electronics will take on a whole new meaning.
What would you like to convey to the general public
about your work?
I think that to the general public I would say that although all my answers
above give the impression that it is all fun and successful, it is just an
impression. In fact, our work consists of working hard and failing most of
the time. The occasional success is what keeps us going. It would be great
if we could convince the general public that what we do in academia is
important for the future despite the fact that most of the time there is no
immediate benefit from our work.
Dr. Nir Tessler
Electrical Engineering Department
The Technion – Israel Institute of Technology
KEYWORDS: SEMICONDUCTOR DEVICE PHYSICS, CHARGE CARRIER
DYNAMICS, QUANTUM WELL LASERS, ORGANIC POLYMERS, ORGANIC
SEMICONDUCTORS, OPTOELECTRONIC DEVICES, CONJUGATED POLYMERS,
NANOCRYSTAL QUANTUM DOTS.