In this work, we proposed a novel and ultra-simple all fluorescent di-chromatic white organic light-emitting diodes (WOLEDs) containing only three non-doped organic layers, which are yellow emitting hole-transport layer, blue emitting electron-transport layer, and charge adjusting layer inserted between hole- and electron-transport layers. White light emission can be realized by simultaneously combining complementary emissions of hole- and electron-transport layers. Based on this structure, a series of all fluorescent di-chromatic WOLEDs were developed, and it was demonstrated the emission spectra could be easily improved by simply changing the thickness of charge adjusting layer. As a consequence, the optimized di-chromatic WOLED achieves a high color rendering index (CRI) of 86, to the best of our knowledge, which is among the highest CRI for such simple structures reported in the literatures. And the resulting device also exhibits high color stability with a slight change of (0.00, −0.01) for CIE coordinates at a wide luminance range from 1011 cd/m² to 9310 cd/m². Moreover, efficiency roll-off is rarely observed for target device before luminance reaching 10,000 cd/m². Such high device performance can be attributed to i) absolutely complementary emissions for hole- and electron-transport layers; ii) a balanced excitons distribution on two transport layers; and iii) a wide carriers recombination zone extending throughout both transport layers. We believe this work will provide a guide to develop simplified but high performance WOLEDs.

在这项工作中，我们提出了一种新颖且超简单的全荧光双色白色有机发光二极管 (WOLED)，仅包含三个未掺杂的有机层，即黄色发光空穴传输层、蓝色发光电子传输层，以及插入空穴和电子传输层之间的电荷调节层。白光发射可以通过同时结合空穴和电子传输层的互补发射来实现。基于这种结构，开发了一系列全荧光双色WOLED，并证明通过简单地改变电荷调节层的厚度可以很容易地改善发射光谱。因此，据我们所知，优化的双色 WOLED 实现了 86 的高显色指数 (CRI)，这是文献中报道的这种简单结构的最高 CRI 之一。并且由此产生的设备还表现出高颜色稳定性，在从 1011 cd/m 起的宽亮度范围内，CIE 坐标的轻微变化为 (0.00, -0.01)²至 9310 cd/m ²。此外，在亮度达到 10,000 cd/m ²之前，很少观察到目标器件的效率下降。如此高的器件性能可归因于 i) 空穴和电子传输层的绝对互补发射；ii) 两个传输层上的平衡激子分布；iii) 一个宽的载流子复合区，贯穿两个传输层。我们相信这项工作将为开发简化但高性能的 WOLED 提供指导。