Study of blue organic light emitting diode by inserting a red dye ultra thin layer at the emitting layer

Experiments of inserting an ultra thin layer of DCJTB at three different levels in a blue emitter layer of a blue device, ITO/CuPc/NPB/TBADN/Alq/LiF/Al, were carried out. The spectra of these devices indicate that the recombination zone is chiefly located near the NPB/TBADN interface, implying that TBADN is capable of electron transport. The inserted DCJTB at TBADN/Alq interface has no contribution to emission, leaving only the blue emission from TBADN, even at high voltage. However, it improved the stability of the device; the half lifetime was prolonged twice more and the rise of applied voltage during ageing was suppressed from 3 V to 0.4 V.