Two notes

A few weeks ago, Heliatek managed to take the lead for organic solar cell efficiencies, achieving 8.3% confirmed power conversion efficiency on 1.1cm2 active area with vacuum deposited small molecules. Madeira Rainbow in AutumnThe device was a tandem. Thomas Körner, VP of Sales, marketing and Business Development at Heliatek, added

The first products should be coming onto the market at the start of 2012.

Good!

Second, you may remember my post on photocurrent in organic solar cells back in July. It was inspired by a comment I wrote on a paper by Street et al, who proposed monomolecular recombination to dominate the loss of free charges in organic bulk heterojunction solar cells. My comment and Bob Street’s reply to it are now online at Phys Rev B. I’ll not comment this interesting exchange any further (unless requested by you;-), so read and think for yourself!

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7 thoughts on “Two notes”

  1. Got a question: Why is it only “8.3% confirmed power conversion efficiency” when I just recently read an article with CIGS on polyimide/polymer substrate achieving 11-12 % cell efficiency. Aren’t these cells organic too or I am completely wrong here? Best, Rob

    1. Hi! The term organic solar cell corresponds to the material combination used for the active layer: all carbon based. Cu(In,Ga)Se2, the active layer material reaching just above 20% on glass substrate and the numbers you quote on polyimide/polymer substrate, is an inorganic composite semiconductor. As only the substrate was organic in the case you state, this does not count as efficiency for an organic solar cell. Nevertheless, a very nice material system: did my PhD on this (well, couple of years back;-). Best, C

      1. Indeed, it’s an interesting one! Currently I’m writing a paper about this system and compare it to convetional TFPV on soda lime glass. So why is there so much interest in organic photovoltaics cells, if there is a different flexible solar cell with better performance out there i.e. CIGS on PI. Are production costs again expected to be lower than with flexible inorganic cells. I mean flex. inorganic cells could reach efficiency of 15% within the next years whereas for organic solar cells it’s still a long way to go. So what makes it so interesting for many researchers?

        Best Robert

      2. You could as well ask why people have started with CIGS solar cells, which were started on rigid substrates, when already silicon solar cells with better efficiencies where present. Actually, 9 years back I gave a talk on device lifetime testing of CIGS solar cells, and was asked just that question;-)

        Of course your question was more precise and deserves a better answer than that! CIGS is nice, and I hope it will gain market share. Its two only severe problems I see are (1) the complex material combination with four to five elements (in addition to Cu, In, Ga, Se also often sulfur, and Na also having an important role) in the active layer. And (2), in comparison to organic solar cells, it needs higher processing temperatures (e.g., sputtering and rapid thermal annealing, maybe at 550 degree C), but can even be printed.

        Polymer-fullerene solar cells or organics in general are in my opinion not thought as replacement for the more established inorganic solar cell technologies. However, they can be printed at high speed at room temperature, suitable for mass production, and thus have the potential to be processed more cheaply. Also, if required, the colour of the active layer can be adjusted – which is rather a niche market, but as I said, it is not thought to replace other technologies. Last not least, the chemistry and physics involved are very interesting from a fundamental point of view (which is, incidentally, my point of view;-)

        Best, C

  2. I’m curious what the efficiency is when it is scale up to a larger area. 8.3% for a such a small active area sounds fine but if its 1-2% for a square meter then we have a very long way to go.

    1. Scaling up is an art in itself. Nevertheless, for polymer-fullerene solar cells, the efficiency record tables by Martin Green show a 3.5% submodule with more than 200 cm2 by Solarmer. Heliatek managed to due a 7.2% module with more than 70 cm2 active area (accounting for the whole area including the metal grid, it was 5.8%, I believe). Still a way to go, but quite promising.

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