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Although I hope I can post something more substantial next week, but do not want to promise what I may not be able to keep…
Organic solar cells:
- Press release by Heliatek: organic module production facility opened in Saxony, Germany
Science Management and Marketing:
- Jessica Seeliger for Nature, Scientists must be taught to manage: about skills for starting a lab
- Martin Fenner, One-click science marketing: how to make your research more visible with online tools. Martin Fenner is also a blogger. Related: Nature Materials Editorial The scientific marketplace and an interview with Mark Kuchner about his book “Marketing for Scientists”
- I like this one most: Richard Hamming about You and Your Research. See also The researcher’s blog for more relevant links, e.g. a nicely typset transcript of the talk.
- Jon Gertner for NY Times, True Innovation: about how Bell Labs managed to be so innovative
- Follow up on the Elsevier story by Kent Anderson. Related: Elsevier’s press release, and the Price Survey 2011 by Library Journal for your reference.
- some anti-procrastination tips by Matt Might: Productivity tips, tricks and hacks for academics
- another Nature Editorial, here the comment by ars technica: If you want reproducible science, the software needs to be open source
- ACSnano Editorial: Recycling Is Not Always Good: The Dangers of Self-Plagiarism
German physical society (DPG) spring meeting in Berlin is still ongoing, although I had to leave already. 6000 (mostly german) physicists on the TU Berlin Campus, nice place to be!
and nothing else.
- Science writer Don Monroe summarises recent research on periocally arranged graphene which interesting light absorption properties: Graphene Arrays Could Be Perfect Absorbers
- MIT technology review’s Katherine Bourzac on A Leap Forward for Plastic Solar Cells on Yang Yang‘s (UCLA) 10.6% record efficiency organic solar cells based on new polymers from Sumitomo Chemical. See also the press release by UCLA
- @joergheber, editor of Nature Materials, twittered his scepticism (not concerning the research, but the outlook) concerning a recent press release from University of Cambridge. Jörg’s followup message was this one…. Read for yourself, but I think he has a point.
- Climate sceptics on the go, via /.: Don’t Worry About Global Warming, Say 16 Scientists in the WSJ; I am no climate scientist, but what I read usually points in the other direction… at least judging from most scientists with peer reviewed publications in contrast to non-peer reviewed “scientists”. Nevertheless, the scientists cited above seem to be real ones, although (mostly?) not with scientific background related to the global climate
- we have a similar discussion here in Germany, with RWE manager Fritz Vahrenholt writing a book trying to confute evidence of global warming, relating any temperature change to the solar activity: summary by Die Zeit (german, google translate) and an article (again Die Zeit) by Toralf Staud, refuting the seven main theses of Vahrenholt ( german, google translate).
- Chronical of higher education summarised the Elsevier boycott. See also The Economist and Nature
- If you do not boycott Elsevier, you may be interested in the booklet Charting a Course for a Successful Research Career by Prof. Johnson, available for free on the sciverse website
- mini statement about the importance of rewriting for better writing of manuscripts etc
- I liked Roman Cortes’ short note on Monte Carlo methods: beautiful!
- douglaswray explains social media
- comment on balancing collaboration and competition for young scientists by Lydia Murray
- Matt Ford, ars technica: Survival in academia, the tenure track not taken
- Article level metrics (in contrast to impact factor) by altmetric with their Bookmarklet
- The coffee setup 2010, though still uptodate, by Marco Arment
- Nature editorial on Tough choices: Scientists must find ways to make more efficient use of funds — or politicians may do it for them and Feature Funding: Got to get a grant
- Alternative for your paper collection now also for windows: Papers by Mekentosj
- German profs underpaid, court says by Quirin Schiermeyer
- blog entry by Hamish Johhnston at physicsworld.com on pondering the power law
Hi, a link list just to keep you occupied;-)
- From December 2011, but nevertheless interesting: critical comment by Joerg Heber, senior editor of Nature Materials, on Organic Solar Cells.
- Criticism of publisher Elsevier becomes louder again (some history of it in the previous link = Wikipedia entry): the mathematician Gowers speaks out in his blog post Elsevier — my part in its downfall (and a follow up post here), and PZ Myers rants Elsevier = Evil in his blog. There is even a website where you can sign upto protest against Elsevier’s practices of driving prices for their journals very high, thecostofknowledge.com. I have to admit I did not do it; just now a book was released by Academic Press (which is an Elsevier brand) with a chapter by me, and also I’d somehow feel strange to boycott one of the few journals (or even the only one?) on organic electronics by Elsevier, the one with just that name. Nevertheless, I agree that information should be made widely available, specifically if funded with public money. That is one of the reasons why I upload most of our articles to the arXiv.org e-print archive.
- Essay by Santiago Alvarez on the wide range of different arrows chemists use… Chemistry: A Panoply of Arrows.
- Adv Funct Mater editorial by Dave Flanagan: More Fundamental Understanding In Materials Science
- Nature News by Jim Giles, Going paperless: The digital lab on using Ipad as your notebook with commercial labbook software.
- Did I link to this nature education piece on English communication for scientists already? I particularly liked the comic on the first page;-)
- The voice of science: let’s agree to disagree by Daniel Sarewitz about the importance of disagreements.
Next week a round of referees will come to Würzburg to decide on another set of grant proposals, so I’ll go back to my preparations now…
Two days ago, a paper considering the role of the “quasiflat band” case in bulk heterojunction solar cells by device simulations was published online [Petersen 2012]. It is critical of the pseudosymmetric photocurrent found and interpreted by [Ooi 2008] and later also ourselves [Limpinsel 2010]. In order to focus on the physical relevance of the (non)symmetry of the photocurrent, the paper by Petersen et al neglects a field dependent photogeneration. As some good points are raised, read the new paper if you are interested in the photocurrent.
[Update 2.4.2012] Another paper showing that band bending is not needed to explain the particular shape of the photocurrent: [Wehenkel 2012].
I will come back to field dependent photogeneration later, it is still intruiging: also here, the photocurrent should (and will be) complemented by pulsed measurements such as time delayed collection field, see e.g. [Kniepert 2011].
As I won a proposal today, I feel up to contributing once again some physics to this blog… I know, it has been a long long wait. So today it is time to consider some fundamentals of charge transport, as this is not only important for the extraction of charge carriers from the device (see earlier posts on mobility and efficiency, surface recombination velocity and photocurrent) but also the nongeminate recombination (see e.g. photocurrent part 2 and 3).
In disordered systems without long range order – such as an organic semiconductor which is processed into a thin film by sin coating – in which charge carriers are localised on different molecular sites, charge transport occurs by a hopping process. Due to the disorder, you can imagine that adjacent molecules are differently aligned and have varying distances across the device. Then, the charge carriers can only move by a combination of tunneling to cover the distance, and thermal activation to jump up in energy. In the 1950s, Rudolph A. Marcus proposed a hopping rate (jumps per second), which is suitable to describe the local charge transport. By the way, he received the 1992 Nobel prize in chemistry for his contributions to this theory of electron transfer reactions in chemical systems. Continue reading “Charge transport in disordered organic matter: hopping transport”
Hi there, I am late again, but nevertheless: a happy and successful year 2012!
Press release of Heliatek: Heliatek achieves new world record for organic solar cells with certified 9.8 % cell efficiency. Evaporated small molecule tandem with area above 1cm2. Very good! Also, Mitsubishi Chemical has reached 10.1% efficiency on solution processed small molecules.
Nature looks back at the science year 2011: 365 days: Images of the year.
Interesting, although not related to physics: Syllabus for David Foster Wallace’s class “English 102-Literary Analysis: Prose Fiction Fall ’94”. Clear rules, yeah! Forgot who linked to it, sorry. Continue reading “2012”
Already 8 weeks past, recently some Videos (well, stills of the slides plus audio) of the Solar and LED Session of the SPIE Optics and Photonics 2011, San Diego went online.
Here are two or three which might interest you (well, they got my attention;-) but there is more to be found on the above mentioned web site – although I had to modify the settings of my ad blocker to be able to watch. No, there are no ads; still…
Before you scroll down, let me mention some other “findings” of potential interest:
- How Google Went Solar by Dan Auld about Big G’s 1.65MW array, and how to get most out of it.
- Then, a nice rant on the climate debate and how news media, trying to be biased, do become very biased… read Diamond planets, climate change and the scientific method by Matthew Bailes. You can see it as a kind of (inofficial) editorial for the last linked article, Who’s your expert? The difference between peer review and rhetoric by Ove Hoegh-Guldberg.
- Another one on organic photovoltaics, Paper solar cells by 2015 (Disclaimer: I was involved in one of these projects. Um ;-).
- Totally unrelated, PhDComics on Writing and Figures…
- Even more unrelated, and not funny: Sitting and Standing at work, finally.
- The most efficient flexible solar cells are not organic, but made from CIGS: Highly efficient Cu(In,Ga)Se2 solar cells grown on flexible polymer films (Nat Mater).
- Alternatively, Silicon Ink can be used, as Bill Scanlon writes.
- Stephen Wolfram on the Advance of the Data Civilization: A Timeline
- Some lessons learned by Chris Dixon; while being about getting a job or your startup funded, it is somewhat applicable to carreers in science.
- The Scientist on the Perfect Poster.
- Nature News on the The reasons for retraction.
But now to these SPIE presentations [Update: WordPress does not accept the embedded vidos, so here just the links to the videos].
James Durrant, Imperial: Charge photogeneration and recombination in organic solar cells
Continue reading “SPIE Pickings”
I have looked in the mirror every morning and asked myself: “If today were the last day of my life, would I want to do what I am about to do today?” And whenever the answer has been “No” for too many days in a row, I know I need to change something.
I covered the photocurrent already before, for instance here. I pointed out that from the light intensity dependence of the short circuit current, it is impossible for many typical conditions to unambiguously determine the dominant loss mechanism or even the recombination order (1st (often called monomolecular, but not my favourite term;-) or 2nd order of decay).
If, however, you know (or guess) that the recombination order is two, you can use the above mentioned vs. data to determine which fraction of charges is lost to bimolecular recombination, . This was shown recently by [Koster 2011]. For , they found . Although I was not able to follow the exact derivation ([Update 5.4.2011] it can be derived by solving a simple differential equation, ), it seems to work. Easy method, although make sure not to have too much space charge in your device – even at the contacts, induced by low (ohmic) injection barriers (we compared it to our device simulation, and then you get significant deviations)! In my opinion, the latter point is not stressed enough in the paper, despite the nice approach. Continue reading “Photocurrent again”