Recently, organic light-emitting diodes (OLEDs) are becoming increasingly attractive to information security, wearable healthcare, and other fields. These fields propose different requirements for performances of OLEDs, especially for voltage-controlled color tunability. In this study, it is proposed to use an ultrathin layer consisting of thermally activated delayed fluorescence (TADF) material as an emitting layer of OLEDs. On the one hand, compared to devices with an ultrathin phosphorescent emitting layer, the OLEDs with TADF show observable color-tunability. On the other hand, the color-tunable OLEDs with TADF show much higher efficiency than the color-tunable fluorescent OLEDs. It demonstrates that the reverse intersystem crossing process not only enhances the exciton utilization efficiency but also leads to an insufficient host-guest energy transfer. With this strategy, a color-tunable OLED is achieved with an external quantum efficiency about 8% and shows color variations over (0.04, 0.08) when its bias voltage increases from 4 to 8 V. By combining with a patterned mask technique, the color-tunable OLEDs can potentially be applied to the field of anti-counterfeiting and status lighting.

中文翻译：

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具有超薄热激活延迟荧光发射层的颜色可调有机发光二极管

最近，有机发光二极管 (OLED) 在信息安全、可穿戴医疗保健和其他领域的吸引力越来越大。这些领域对OLED的性能提出了不同的要求，尤其是对电压控制的颜色可调性。在这项研究中，建议使用由热激活延迟荧光 (TADF) 材料组成的超薄层作为 OLED 的发光层。一方面，与具有超薄磷光发光层的器件相比，具有 TADF 的 OLED 显示出可观察到的颜色可调性。另一方面，具有 TADF 的颜色可调 OLED 显示出比颜色可调荧光 OLED 更高的效率。这表明反向系统间穿越过程不仅提高了激子利用效率，而且导致主客体能量转移不足。通过这种策略，实现了一种颜色可调的 OLED，其外部量子效率约为 8%，并且当其偏置电压从 4 V 增加到 8 V 时，颜色变化超过 (0.04, 0.08)。通过结合图案化掩模技术，颜色-可调谐OLED可潜在应用于防伪和状态照明领域。