20. March 2014
Just a brief note, I moved from Würzburg to the Institute of Physics at Chemnitz University of Technology this March, starting a new group. At present I have one PhD position open on Organic Photovoltaics – funded by the University, therefore including some teaching duty in German. Have a look here (in German) or drop me a line if you are interested. Cheers,
25. August 2013
Some links I found interesting since the last time… partly older stuff, though.
21. August 2013
In a “recent” post (just 3 posts but 10 months ago;-) I wrote once again on the derivation of the Langevin recombination rate for nongeminate recombination. The question is, is Langevin recombination really what governs the charge carrier loss rate in organic solar cells?
Recombination of electrons with holes is usually a 2nd order decay. As electrons and holes are photogenerated pair wise, the respective excess charge carrier concentrations are symmetric, . Then a recombination rate is
where the recombination prefactor could be a Langevin prefactor – more on that later. In a transient experiment with a photogenerating, short laser pulse at , the continuity equation for charge carriers (here, e.g. electrons) under open circuti conditions (no external current flow, for instance if the experiment is done on a thin film without electrodes)
for (as the generation was only at ).
If all electrons and hole are available for recombination (i.e., can reach all other charge carriers and can be reached by them), then the recombination rate and the continuity equation for yield
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18. March 2013
On 11th of February (my birthday, incidentally), our 2nd child was born: Nicolas Jacob. We are so happy, as is our 2 year old daughter Chiara.
Even with only one kid, it was already rather quiet on this blog in the last months (well, 2 years…). Still, I do have some hope to be able to dedicate one or the other quiet minute to write some urgently needed updates to previous posts. All the best, Carsten
23. October 2012
Related to this post on Konarka’s bankruptcy: According to a range of news sites, including pv-tech.org, the german company Belectric has acquired Konarka Technologies. Find the press release here (pdf).
The system integrator Belectric is situated in Lower Franconia, less than 50km from Würzburg and less than 10km from where I live. Let’s keep our fingers crossed!
16. October 2012
Nongeminate recombination is the major loss mechanism for state-of-the-art organic solar cells. In an early blog post
, I showed how the Langevin recombination was derived.
Although there is more to nongeminate recombination than just this mechanism, it is still instructive and also relevant to trap-assisted recombination mechanisms, due to its mobility-containing prefactor.
[Nenashev 2010] pointed out that in the derivation of the Langevin recombination,
since the electric field scales as r−2 and the surface area of the sphere scales as 2, the value of r chosen is unimportant, leading to a simple solution with constant electron den- sity, thus justifying the neglect of diffusion.
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2. June 2012
Via Juan Bisquert’s post: solar cell company Konarka filed for bankrupty yesterday according to Businessweek. It is always hard to be the first… Konarka received its first venture capital in mid 2001.
Howard Berke, CEO of Konarka:
This is a tragedy for Konarka’s shareholders and employees and for the development of alternative energy in the U.S.
Let’s hope that our friends from Konarka find other suitable positions, and that other companies such as Heliatek take up the lead!
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