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OLED 1 Comment
I missed this last week whilst on holiday, but on 18.03.08 Chem. Comm. published a Chinese group’s work on the development of an Iridium dopant for OLEDs which allows, potentially, 100% conversion of energy into light!
The inclusion of the dopant highlights the importance of heavy metals in (ironically termed??) OLEDs. Fully organic LEDs cannot achieve better than 25% due to the nature of the excited states being formed and the ratio of emissive:non-emissive ‘excitons’ (N.B. this isn’t the best use of the word but allow me some poetic license here please!!). Inclusion of the heavy metal (sometimes platinum, more often iridium) allows conversion of the non-emissive ‘excitons’ to be converted to emissive ones (intersystem crossing - see a jablonski diagram for more info on this!).
Totally pointless picture but looks pretty - taken from
RSC news site.
The Chinese group use a large highly conjugated ligand which still allows high solubility, and best of all, it was all done serendipitously! The biggest breaks usually are done by luck…
Read the paper for more:
Tong, B., Mei, Q., Wang, S., Fang, Y., Meng, Y., Wang, B. (2008). Nearly 100% internal phosphorescence efficiency in a polymer light-emitting diode using a new iridium complex phosphor. Journal of Materials Chemistry DOI: 10.1039/b800977e
interestedinscience.com © 2008
Ha ha! At last some certifiable published research/progress on the flat-screen/organic electronics-printing front (sorry for that appauling intro…it’s early).
Japanese scientists have published in PNAS (see citation at bottom - next edition) a method to reliably print flat screen panels using a fancy new inkjet style printer (see also BBC News). The technique allows them to circumvent the problems of todays silicon-based flat panel printing processes which in order to obtain maximum purities and performances have yielded to higher processing temperatures, increased manufacturing costs, and thus a higher price for the consumer - exactly what plastic electronic technology is designed to help combat.
The inkjet printers are able to print dots of 1 micron (a millionth of a meter, 1×10-6m, a thousandth of a millimeter…very small!) on to a flexible organic semiconductor. Current printing techniques are limited in their abilities to replicate the resolutions achieved by silicon-based devices and other lithographic techniques for several reasons - one being surface tension of the inks. This new printing technique allows droplet volumes of less than 1 femtolitre - a millionth that which recent techniques allowed.
All in all…yes! Very happy with this development.
See citation below for full article…
Sekitani, T., Noguchi, Y., Zschieschang, U., Klauk, H., Someya, T. (2008). Organic transistors manufactured using inkjet technology with subfemtoliter accuracy. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0708340105
interestedinscience.com © 2008
Ok, completely off the beaten track for me and into the world of theoretical physics. Here is a journal from scientists in Scotland and Germany claiming to be able to create the event horizon of a black hole - you know, where light and matter (and my spare car key I assume) are lost forever.
It is believed by some that it will allow them to study the physics of the particles created in/emitted from the black holes we know are more regularly situated in space, as these are invariably surrounded by dust, gases and other space-borne artifacts.
This image can be seen in its original context at http://www.st-andrews.ac.uk/~ulf/fibre.html.
I love it. I’m scared by it but I am amazed at what they are attempting.
For a more thorough read follow the link above or check out the paper…
The article is appearing in science.
Philbin, T.G., Kuklewicz, C., Robertson, S., Hill, S., Konig, F., Leonhardt, U. (2008). Fiber-Optical Analog of the Event Horizon. Science, 319(5868), 1367-1370. DOI: 10.1126/science.1153625
interestedinscience © 2008
