2 February 2001 High brightness and efficiency green light-emitting diodes based on fluorene-containing conjugated polymers and associated blends
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Abstract
We report on the fabrication and properties of single layer green light-emitting diodes (LEDs) based on fluorene- containing conjugated polymers and associated blends. We have used a new green fluorene based conjugated polymer (namely 5BTF8) as the emissive material as well as the host in blends with a guest hole transport triarylamine/fluorene copolymer (namely BFB) to fabricate bright and efficient single layer green polymer light-emitting diodes (PLEDs). An enhancement in both the electroluminescence quantum and power efficiency is seen for the blend. This observation indicates that the hole transport material leads to a significant improvement in hole injection and transport and thus to an improved charge carrier balance factor. A higher brightness and a lower turn on as well as operating voltage are also achieved for the blend. The emission from a green single layer LED with 5BTF8/BFB (4/1) as the emissive layer reaches a maximum brightness of 35000 cd/m2 with a maximum external quantum efficiency of 1.3% or 4.2 cd/A and a maximum power efficiency of 2.5 lm/W. Novel small area LEDs were also fabricated using a SiN insulating layer on top of the ITO that allowed much higher brightnesses to be achieved compared to the standard area LEDs due to the reduced heating and therefor to a better thermal management of the device. The emission from a PEDOT/5BTF8 small area LED reached a maximum brightness of 155,000 and 6,500,000 cd/m2 in DC and pulsed mode, respectively.
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Leonidas C. Palilis, Leonidas C. Palilis, Chris I. Wilkinson, Chris I. Wilkinson, David G. Lidzey, David G. Lidzey, Donal D. C. Bradley, Donal D. C. Bradley, Michael Inbasekaran, Michael Inbasekaran, Weishi W. Wu, Weishi W. Wu, } "High brightness and efficiency green light-emitting diodes based on fluorene-containing conjugated polymers and associated blends", Proc. SPIE 4105, Organic Light-Emitting Materials and Devices IV, (2 February 2001); doi: 10.1117/12.416921; https://doi.org/10.1117/12.416921
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