Start at the start...
Well; what are OLEDs? Organic light-emitting diodes are a class of materials that emit light by electroluminescence. If that sentence made no sense to you then I will post up an even more simplified description of some basic chemistry soon.
By altering the molecules, the HOMO-LUMO gap can be tuned to allow red, green and blue light to be generated, in turn allowing full colour displays to be fabricated. Because the molecules are organic in nature (essentially plastics), a revolutionary new way of coating displays using a modified version of ink-jet printing has been developed (largely between CDT and Seiko-Epson). This allows facile device fabrication as opposed to traditional CVD techniques. The displays themselves are emissive rather than being based on negative technology like LCDs. LCDs require a back-light which leads to low contrast ratios (grey "blacks"), extra bulk and power consumption and in some cases "backlight bleeding" where the backlight leaks through small gaps around the edge of the screen. Other features include 180 degree viewing angles and microsecond response times (compared to 140 degree view angles and millisecond responses of LCDs). If the materials are deposited onto a flexible substrate then flexible or "roll-up" displays can be created.
With all these factors combined, it should be possible to produce very cheap, thin, flexible and low power displays. Indeed, OLEDs launched commercially in 1997, but in limited ways. Most displays were monochrome (shaver battery meters, 2nd screens on phones) but soon became full colour. Several demonstration 40" screens are currently doing the rounds at trade shows but aren't expected to launch until late 2007.
So, what is the purpose of further research? If products have launched, haven't we missed the boat? Not necessarily, advancements are making purer colours, higher efficiencies, longer lifetimes and simplifying device fabrication. My work is an attempt to produce materials that can produce easy to make devices that do not require multiple layers (see next post) - be they singlet emitters or triplet emitters. Over the next weeks and months I'll keep you updated of major events in the OLED world and my progress in the lab.
A few major things comming up are a possible presentation to an organic symposium in York, my first paper on bipolar triad molecules and a poster at Functionalised Pi Systems 7 in Osaka.
Next up on here will be a beginners guide to chemistry(!) and the principles behind electroluminescence.
By altering the molecules, the HOMO-LUMO gap can be tuned to allow red, green and blue light to be generated, in turn allowing full colour displays to be fabricated. Because the molecules are organic in nature (essentially plastics), a revolutionary new way of coating displays using a modified version of ink-jet printing has been developed (largely between CDT and Seiko-Epson). This allows facile device fabrication as opposed to traditional CVD techniques. The displays themselves are emissive rather than being based on negative technology like LCDs. LCDs require a back-light which leads to low contrast ratios (grey "blacks"), extra bulk and power consumption and in some cases "backlight bleeding" where the backlight leaks through small gaps around the edge of the screen. Other features include 180 degree viewing angles and microsecond response times (compared to 140 degree view angles and millisecond responses of LCDs). If the materials are deposited onto a flexible substrate then flexible or "roll-up" displays can be created.
With all these factors combined, it should be possible to produce very cheap, thin, flexible and low power displays. Indeed, OLEDs launched commercially in 1997, but in limited ways. Most displays were monochrome (shaver battery meters, 2nd screens on phones) but soon became full colour. Several demonstration 40" screens are currently doing the rounds at trade shows but aren't expected to launch until late 2007.
So, what is the purpose of further research? If products have launched, haven't we missed the boat? Not necessarily, advancements are making purer colours, higher efficiencies, longer lifetimes and simplifying device fabrication. My work is an attempt to produce materials that can produce easy to make devices that do not require multiple layers (see next post) - be they singlet emitters or triplet emitters. Over the next weeks and months I'll keep you updated of major events in the OLED world and my progress in the lab.
A few major things comming up are a possible presentation to an organic symposium in York, my first paper on bipolar triad molecules and a poster at Functionalised Pi Systems 7 in Osaka.
Next up on here will be a beginners guide to chemistry(!) and the principles behind electroluminescence.
posted by Kiran at 4:39 PM
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