We selectively improved the viewing angle characteristics and light extraction efficiency of blue thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) by tailoring a nanofiber-shaped Si₃N₄ layer, which was used as an internal scattering layer. The diameter of the polymer nanofibers changed according to the mass ratio of polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) in the polymer solution for electrospinning. The Si₃N₄ nanofiber (SNF) structure was fabricated by etching an Si₃N₄ film using the PAN/PMMA nanofiber as a mask, making it easier to adjust parameters, such as the diameter, open ratio, and height, even though the SNF structure was randomly shaped. The SNF structures exhibited lower transmittance and higher haze with increasing diameter, showing little correlation with their height. However, all the structures demonstrated a total transmittance of over 80%. Finally, by applying the SNF structures to the blue TADF OLEDs, the external quantum efficiency was increased by 15.6%. In addition, the current and power efficiencies were enhanced by 23.0% and 25.6%, respectively. The internal light-extracting SNF structure also exhibited a synergistic effect with the external light-extracting structure. Furthermore, when the viewing angle changed from 0° to 60°, the peak wavelength and CIE coordinate shift decreased from 20 to 6 nm and from 0.0561 to 0.0243, respectively. These trends were explained by the application of Snell’s law to the light path and were ultimately validated through finite-difference time-domain simulations.

中文翻译：

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通过易于定制的 Si3N4 纳米纤维结构选择性增强蓝色热激活延迟荧光有机发光二极管的视角特性和光提取效率


我们通过定制纳米纤维状Si ₃ N ₄ 选择性地改善了蓝色热激活延迟荧光（TADF）有机发光二极管（OLED）的视角特性和光提取效率层，用作内部散射层。聚合物纳米纤维的直径根据静电纺丝聚合物溶液中聚丙烯腈（PAN）和聚甲基丙烯酸甲酯（PMMA）的质量比而变化。使用PAN/PMMA纳米纤维蚀刻Si ₃ N ₄ 薄膜制备了Si ₃ N ₄ 纳米纤维（SNF）结构作为掩模，即使 SNF 结构是随机形状的，也可以更容易地调整直径、开口率和高度等参数。随着直径的增加，SNF 结构表现出较低的透射率和较高的雾度，与高度的相关性很小。然而，所有结构的总透射率都超过80%。最后，通过将SNF结构应用于蓝色TADF OLED，外量子效率提高了15.6%。此外，电流效率和功率效率分别提高了23.0%和25.6%。内部光提取SNF结构还表现出与外部光提取结构的协同效应。此外，当视角从0°变为60°时，峰值波长和CIE坐标偏移分别从20 nm减小到6 nm，从0.0561减小到0.0243。这些趋势通过将斯涅耳定律应用于光路来解释，并最终通过有限差分时域模拟得到验证。