Mobility and Efficiency of Polymer Solar Cells

Joshua TreeDisordered organic materials inhibit charge carrier mobilities which are orders of magnitude lower than for inorganic crystals. First thing missing in disordered matter is the regularly ordered lattice of atoms, where the charge carriers can delocalise, leading to band transport. Second thing is the generally lower interaction between adjacent molecules, which is due to weaker bonding and larger distances. The transfer integral, the value of which goes exponentially down with distance, to get from one to the other molecule is too low for delocalisation. Thus, in terms of charge carrier mobility, think 10-2cm2/Vs for disordered organics (if you are lucky) vs. at least 102cm2/Vs for ordered inorganics.

How much does a weak charge transport limit the performance of organic solar cells? How bad is it?

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Industry Again…

Plextronics just opened its first manufacturing development line for organic ink (in contrast to the inorganic ink news from last week) to be used in polymer solar cells. Boston SkylineA stage prior to production, this is still good news for the organic photovoltaics community. The spin-off from Carnegie Mellon University, founded in 2002, describes its focus as being

on organic solar cell and organic light emitting diodes (OLED), specifically the conductive inks and process technologies that enable those and other similar applications.

I mentioned Plextronics already last year, as they presented the (up to now, I believe) highest certified power conversion efficiency for an organic solar cell.

Indeed, industry news again… for next time, I promise more fundamentals;-)

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Inkjet Printing of Inorganic Solar Cells

Last week, the german company Roth and Rau – supplier of plasma process systems for the photovoltaics industry – had Newbury Street, Bostona press release: they just finished the installation of a new production line for inkjet printing of silicon solar panels, together with Innovalight. See here (or in german here). Innovalight has developed the silicon ink technology in recent year, in collaboration with NREL and others. Low level of details, as typical for press realeases, but certainly interesting. And a competitor for printed organic solar cells even before they are in the production stage, even if on track.

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Personal news, and a happy new year 2009

Dear valued reader, Anette Hammer)' on Flickr.complease allow me to share some personal news:

Just married !

On the 20th of December 2008, Anja and I celebrated our civil wedding, our “way into happiness” as we call it, in my home town Wuppertal! Afterwards we spent two very relaxing weeks on vacation, enjoying togetherness, thus regaining vigour and inspiration after a laborious year.

That news given, you will certainly believe me that for us this will be an excellent new year 2009, with many more as good ones to follow. Please accept my best wishes for a healthy, funny, splendid year to come.

All the best,


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