Charge carrier dynamics and degradation phenomena in organic light-emitting diodes doped by a thermally activated delayed fluorescence emitter
Charge carrier dynamics and degradation phenomena in organic light-emitting diodes doped by a thermally activated delayed fluorescence emitter
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DOI：
10.1016/j.orgel.2014.12.009
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发表时间：
2015-02
影响因子：
3.2
通讯作者：
Y. Noguchi;H. J. Kim;R. Ishino;K. Goushi;C. Adachi;Y. Nakayama;H. Ishii
中科院分区：
文献类型：
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作者：
Y. Noguchi;H. J. Kim;R. Ishino;K. Goushi;C. Adachi;Y. Nakayama;H. Ishii
本文报道了热激活延迟荧光发射器掺杂有机发光二极管（OLED）中的载流子动力学及其降解现象；（4,6s）- 2,4,5,6 -四（9h -咔唑-9-基）二苯二腈（4CzIPN）。位移电流测量（DCM）数据显示，1,3,5 -三（1-苯基- 1h -苯并咪唑-2-基）苯的电子传递层（ETL）自发取向极化产生了负界面电荷。界面负电荷作为空穴储集层，将复合区限制在发射层（EML）附近；4,4 ' -双（n -咔唑基）- 1,1 ' -联苯（CBP）： 4CzIPN (5 wt%)/ETL接口。使复合区远离空穴输运层4,4′-双[N-（1-萘基）-N-苯胺]-联苯（α-NPD），抑制了4CzIPN从三重态向α-NPD态的Dexter能量转移，有望获得更好的电致发光效率。此外，我们发现累积的空穴数量与器件老化造成的亮度损失之间存在良好的线性关系。结果表明，CBP降解产物产生的空穴陷阱是导致器件降解的主要因素。我们建议基于电荷载流子动力学的器件架构以获得更好的效率和寿命。
We report on the charge carrier dynamics and their degradation phenomena in an organic light-emitting diode (OLED) doped by a thermally activated delayed fluorescence emitter;(4s, 6s)-2, 4, 5, 6-tetra (9H-carbazol-9-yl) isophthalonitrile (4CzIPN). Displacement current measurement (DCM) data revealed the presence of negative interface charge originating from the spontaneous orientation polarization of the electron transport layer (ETL), 1, 3, 5-tris (1-phenyl-1H-benzimidazol-2-yl) benzene. The negative interface charge acts as a hole reservoir and thus confines the recombination zone near the emission layer (EML); 4, 4′-bis (N-carbazolyl)-1, 1′-biphenyl (CBP): 4CzIPN (5 wt%)/ETL interface. By keeping the recombination zone far from the hole transport layer, 4, 4′-bis [N-(1-naphthyl)-N-phenylamino]-biphenyl (α-NPD), a better electroluminescence efficiency is expected because the Dexter energy transfer from the triplet state of 4CzIPN to that of α-NPD is suppressed. Moreover, we found an excellent linear relation between the accumulated hole amount and luminance losses owing to device aging. The results are consistent with hole traps originating at the degradation products of CBP as the main factor of device degradation. We suggest device architectures based on the charge carrier dynamics for better efficiency and lifetime.