本研究利用一新穎螢光發光體,配搭一優異的元件結構,製備出一高效率紅光有機發光二極體(Organic light-emitting diode, OLED),其在極高亮度下,呈現突破世界紀錄之元件效率,尤其是超越同為紅光的磷光發光體。以在33,000 cd/m2亮度下為例,其外部量子效率超越5%的理論極限,而達8.5%,能量效率為3.0 lm/W,電流效率為13.6 cd/A,均為紅光OLED之世界紀錄。此紅光染料3-(N,N-diphenylamino)-7-di(cyanoyl)-5,5-spirofluorenyl -5H -dibenzo [a,d] cycloheptene (N-STIF-DCN),搭配主體10,10'- di(biphenyl -4-yl)-9,9'-bianthracene (BANE),在高亮度下,能有高效率的原因,可歸因於五點:一、適合紅光染料之良好主體,使發光層為客體紅光放光而非主體放光;二、低的載子注入能障,使載子較容易注入發光層結合成激子及放光;三、好的主客體能量傳遞,能將在主體上產生之激子的高能量轉移至客體上,給客體放光;四、良好的載子侷限,即使在高操作電壓下,載子也不容易從發光層流失,能形成較多的激子並放光;五、主客體能階搭配,在低操作電壓下,激子於客體上再結合及放光,而在高操作電壓下,載子可以有效地在主體上再結合形成激子,並傳遞能量給客體放光。此種主客體能階搭配之元件,能夠在主客體上生成最多激子,因此有別於傳統元件,其元件效率在高操作電壓下具有上升的現象。
We demonstrate at a very high luminance an extraordinary high-efficiency red fluorescent organic light emitting diode (OLED) by using a novel red emitter, 3-(N,N-diphenylamino)-7-di(cyanoyl)-5,5 -spirofluorenyl-5H-dibenzo [a,d] cycloheptene (N-STIF-DCN).The device exhibits, at 33,000 cd/m2 for example, a major peak at 612 nm with an external quantum efficiency of 8.5% with 13.6 cd/A and 3.0 lm/W, The high efficiency oberserved at the extremely high brightness may be attributed to four efficiency-effective architectural factors of the device designed as well as the unique electro-luminance effective material factor of the red dye synthesized. The five efficiency-effective architectural factors are low injection barrier, balanced carrier injection, effective carrier confinement, maximum excitons generation in both host and guest, and effective host-to-guest energy transfer.