We have demonstrated color stable white organic light-emitting diodes (WOLEDs) with bipolar mixed spacer based on ultrathin non-doped phosphorescent emitting layers (EMLs). The introduced bipolar mixing spacer which contributes to the uniform distribution of recombined excitons plays an important role in stabilizing the spectrum. Through different emitters orders: blue/green/orange (named B-G-O) and orange/green/blue (named O-G-B), the thickness ratio of the EML at the anode and cathode side is proved to be the core factor on spectral stability. The spectral stability is attributed to two key mechanisms: sequential energy transfer offsets the change of emission intensity caused by exciton recombination zone (RZ) drift under different voltages, and direct carrier trapping effect compensates the emission intensity at low voltage. The resulting three-color WOLED shows an insignificant chromatic coordinate change of (0.001, 0.001) when the luminance increases from 1000 cd/m² to 10000 cd/m². This discovery provides a significant method for achieving high-performance WOLED with superior color stability.

我们已经证明了具有基于超薄非掺杂磷光发射层（EML）的双极混合间隔物的颜色稳定的白色有机发光二极管（WOLED）。引入的有助于混合激子均匀分布的双极混合隔离剂在稳定光谱中起着重要作用。通过不同的发射器顺序：蓝色/绿色/橙色（称为BGO）和橙色/绿色/蓝色（称为OGB），在阳极和阴极侧的EML的厚度比被证明是光谱稳定性的核心因素。光谱稳定性归因于两个关键机制：连续的能量转移抵消了由激子复合区（RZ）引起的发射强度的变化。）在不同电压下漂移，直接载流子捕获效应补偿了低压下的发射强度。当亮度从1000 cd / m ²增加到10000 cd / m ²时，所得的三色WOLED的色坐标变化很小，为（0.001，0.001）。该发现为实现具有卓越色彩稳定性的高性能WOLED提供了重要的方法。