为了提升绿色有机发光二极管的效率,设计了阶梯能级结构的器件,使得载流子在器件中更有效传输,进而有效减缓了器件效率的衰减。选择热致延迟荧光材料(4s,6s)-2,4,5,6-四(9-氢咔唑-9-基)间苯二腈(4CzIPN)作为发光材料,并将其掺杂到能级匹配的主体材料1,3-二(咔唑-9-基)苯(mCP)中构成发光层,制备了一系列单发光层的绿色有机发光二极管。在发光材料的掺杂浓度为2%(wt,质量分数),发光层的厚度为20nm条件下,制得的器件性能最佳,其启亮电压为3.4V,其最大亮度、电流效率、功率效率和外量子效率分别为20706cd/m2、50.49cd/A、41.96lm/W和16.7%。在亮度为1000cd/m2条件下,其电流效率和外量子效率仍然高达34.06cd/A和11.6%。器件显示主峰位于504nm的4CzIPN特征发射,随着掺杂浓度的提升,越来越多的电子和空穴被4CzIPN分子所俘获,导致主体材料mCP的特征发射峰逐渐减弱。
A series of single light-emitting layer (EML) devices based on thermally activated delayed fluorescence (TADF) emitter were reported to improve the efficiency and simple the structure of device.Due to the relative low-lying energy levels of emitter,(4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) doped 1,3-bis(carbazol-9-yl)benzene (mCP) film was used as EML,when the doping concentration and the thicknesses of EML was 2wt% and 20nm,the optimized device with turn-on voltage,the maximum brightness,external quantum efficiency,current efficiency and power efficiency up to3.4V,20706cd/m2,50.49cd/A,41.96lm/W and 16.7%,respectively,was obtained.Even at the practical brightness of 1000cd/m2,external quantum efficiency and current efficiency as high as 11.6% and 34.06cd/A,respectively,can still be retained.The characteristic emission of 4CzIPN (504nm) can be observed in all these devices,and with the increasing of doping concentration of emitter,more and more holes and electrons were trapping by emitter molecule,so the emission of mCP was decreasing.
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基金资助
吉林省发改委项目(2017C050)
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