Improved OLED Efficiency by Matching Permanent Spontaneous Orientation Polarization of Device Layers.

The effect that permanent spontaneous orientation polarization can have on the performance of an organic light-emitting diode device has received limited attention in recent years and is commonly overlooked. While studies have shown that polarized layers can lead to lower operating voltages due to higher densities of mobile charge carriers, the undesirable reduction of efficiency due to quenching of excitons is also commonly observed. From this perspective, we explore device architectures that utilize molecules that form layers with substantial polarization and use simulation methods to predict the degree of polarization. By employing such materials in both the emissive layer and the adjacent electron-blocking layer, we found that the device's external quantum efficiency is improved when the difference in polarization between the two layers is reduced. We have also found that when mixing two materials, the polarization of the mixed film can be linearly interpolated based on the mixing ratio and polarization of each individual component.