Highly efficient yellow organic light-emitting diodes with slow efficiency roll-off by mixing red and green emissions

In this work, we report the design and optimization of yellow organic light-emitting diodes (OLEDs) with tris [2-(p-tolyl)pyridine]iridium (III) (Ir (mppy)3) doped 4,4′,4′-tris(N-carbazolyl)triphenylamine (TCTA) and bis(2-phenylquinoline) (2,2,6,6-tetramethylheptane-3,5-dionate)iridium (III) (PQ2Ir (dpm)) doped 2,6-bis(3-(9H-carbazol-9-yl)phenyl)phyridine (26DCzPPy) films as green and red light-emitting layers (EMLs). Experimental results demonstrated that the designed double EMLs system is beneficial in carriers' distribution, exciton confinement and reducing triplet exciton quenching because of the matched energy levels and triplet energies of hosts and dopants. Finally, the optimal device showed a very maximal current efficiency of 65.51 cd/A, slow roll-off of efficiency with a very high current efficiency of 63.54 cd/A at 5000 cd/m2, and excellent yellow emission with CIE coordinates of (0.468, 0.493) at 10 mA/cm2. Double light-emitting layers yellow organic light-emitting diodes (OLEDs) with high efficiency and low efficiency roll-off were fabricated by using phosphorescent iridium complexes tris [2-(p-tolyl)pyridine]iridium (III) (Ir (mppy)3) and bis(2-phenylquinoline) (2,2,6,6-tetramethylheptane-3,5-dionate)iridium (III) (PQ2Ir (dpm)) as green and red emitters, respectively. [Display omitted] •Efficient yellow organic light-emitting diodes with double light-emitting layers were designed and fabricated.•The double light-emitting layers system helps to improve electroluminescent (EL) efficiency and reduce efficiency roll-off.•Simplified device structure is efficient in reducing operating voltage and thus improving EL efficiency in turn.