着重对比了在以DCM掺杂Alq3为发光层的红光器件的发光区插入超薄LiF层后器件性能的改善.插入超薄LiF层后,器件的最大工作电流密度为487mA/cm2,相应的最大电致发光亮度为76 740 cd/m2,最大外量子效率为5.9％.器件内量子效率为40％,超过了基于有机荧光小分子发光材料的有机电致发光器件的内量子效率的理论极限值25％.对器件内单线态及三线态激子的形成过程进行了分析,并推测:超薄LiF层的插入提高了器件内单线态电荷转移态/三线态电荷转移态的形成比例,进而提高了器件内单线态激子在激子总数中的比例,最终提高了器件的内量子效率.同时,超薄LiF层的插入改变了发光层内局域的内部电场,使器件的外量子效率不仅没有随电流密度的增加而降低,反而非线件增加.%The performance of two DCM: Alq3 based on red organic light-emitting diodes( OLEDs) were compared. In device A, ultrathin LiF was inserted between emitting layer and electron transporting layer, the other without inserting layer was named device B. As a result, device A showed a maximum EQE( external quantum efficiency) of 5.9% ,which was obtained under the highest brightness 76 740 cd/m2 with current density of 487 mA/cm2. Correspondingly, the internal quantum efficiency of 40% was far exceeded the theoretical upper limit of 25% for fluorescent OLEDs. We attributed the unusual phenomenon to the manipulation of the charge transfer state mixing and the electrical field effect on the excitons.
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