The appropriate hosts of emitting layers (EMLs) play an important role in determining the overall performance of solution-processed phosphorescent organic light emitting diodes (PhOLEDs). We have investigated the effect of three species of host molecules, 1,3-bis(carbazol-9-yl)benzene (mCP), 10-(4-(5,5dimethylbenzofuro[3,2-c]acridin-13(5H)-yl)phenyl)-10-phenylanthracen-9(10H)-one (DpAn-5BzAc) and poly(9-vinylcarbazole) (PVK), on the performance of solution-processed blue and yellow PhOLEDs. We have found that compared to the widely used single-host EMLs, the devices using the binary blend of mCP: DpAn5BzAc as hosts, can achieve more efficient optoelectrical characteristics. The maximum current efficiencies of 11.84 and 16.61 have been realized for blue and yellow OLEDs, respectively. The superior electroluminescence performance for binary blend host-based PhOLEDs was attributed to the enhanced charge carrier balance and multi-component miscibility, which has a dramatic influence on the morphology of the emissive layer. These results demonstrate the great potential of the multi-hosts in solution-processed organic optoelectronic devices. The development of complementary colour OLEDs with blue and yellow can provide a simple approach to fabricate solution-processed white PhOLEDs.
Revealing molecular conformation–induced stress at embedded interfaces of organic optoelectronic devices by sum frequency generation spectroscopy