Development of solution-processed white phosphorescent tandem organic light-emitting devices

The organic light-emitting devices (OLEDs) comprising multiple light-emitting units (LEUs) stacked in series through charge generation layers (CGLs), called tandem OLEDs, have been fabricated to achieve a high luminance and long operational lifetime simultaneously. We developed the fully solution-processed green and white tandem OLEDs using small molecule phosphorescent materials and their record breaking high efficiency. The ZnO nanoparticle / aliphatic amine polymer (PEIE) bilayer serves as the EIL in each LEU, and poly (3,4-ethylenedioxythiophene) : poly (styrenesulfonate) (PEDOT : PSS) is used as the interconnecting conductive layer. Successfully fabricated green and white phosphorescent stacked OLEDs exhibit nearly a twofold higher efficiency than either of the component LEUs.