Department of Materials Science and Engineering, University of Florida , Gainesville, Florida 32611, United States.
CYNORA, GmbH , Werner-von-Siemens-Straße 2-6, Building 5110, 76646 Bruchsal, Germany.
ACS Appl Mater Interfaces. 2017 Nov 29;9(47):41421-41427. doi: 10.1021/acsami.7b13537. Epub 2017 Nov 14.
The understanding and control of the emission zone in organic light emitting diodes (OLEDs) is crucial to the device operational stability. Using the photoluminescence and electroluminescence degradation data, we have developed a modeling methodology to quantitatively determine the length of the emission zone and correlate that with the degradation mechanism. We first validate the modeling results by studying the emitter concentration effect on operational stability of devices using the well-studied thermal activated delayed fluorescent (TADF) emitter (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN), and our results are consistent with previous published data. We further applied this methodology to study the emitter concentration effect using another TADF emitter, 4-carbazolyl-2-methylisoindole-1,3-dione (dopant 1). The results show that the emission zone of the dopant 1 devices is narrower than the 4CzIPN device, leading to faster degradation. While a higher emitter concentration does not result in widening of the emission zone, we were able to widen the emission zone and hence extend the device lifetime using a mixed host.
理解和控制有机发光二极管（OLED）中的发射区对于器件的工作稳定性至关重要。我们利用光致发光和电致发光衰减数据，开发了一种建模方法，定量确定发射区的长度，并将其与降解机制相关联。我们首先通过研究使用经过充分研究的热活化延迟荧光（TADF）发射器（4s，6s）-2,4,5,6-四（9H-咔唑-9-基）间苯二甲腈（4CzIPN）的器件工作稳定性对发射器浓度的影响来验证建模结果，我们的结果与之前发表的数据一致。我们进一步应用该方法研究了另一个 TADF 发射器，即 4-咔唑基-2-甲基异吲哚-1,3-二酮（掺杂剂 1）对发射器浓度的影响。结果表明，掺杂剂 1 器件的发射区比 4CzIPN 器件窄，导致降解速度更快。虽然较高的发射器浓度不会导致发射区变宽，但我们能够使用混合主体来拓宽发射区，从而延长器件寿命。
