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!).

Pretty colours available for OLEDs
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:

ResearchBlogging.orgTong, 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

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