High Efficiency Non‐Doped White Organic Light Emitting Diodes Based on a Bilayer Interface‐Exciplex Structure

High efficiency non‐doped blue and white organic light emitting diodes (OLEDs) are realized by using a bilayer interface‐exciplex (i‐Exc) structure. Since the neutral exciplex are formed at the interface, the interface charge accumulation is reduced, thereby suppressing exciton quenching in the device. With the i‐Exc structure, a maximum external quantum efficiency (EQE) of 23.1% is achieved in the non‐doped blue phosphorescent OLED. Moreover, the white emission can be obtained by inserting an ultrathin orange‐red phosphorescent emitter into the blue devices. The charge trapping in the orange‐red emitter can be suppressed by adjusting the position of the ultrathin orange‐red emitting layer in the device, contributing to superior spectral stability. The WOLED achieves an EQE of 20.0% and exhibits a stable warm white emission. The Commission Internationale de l'Eclairage (CIE) coordinates of WOLED are (0.41, 0.40) at 5 V and slightly change to (0.40, 0.41) at 9 V.