Reliability comparison of BTEL and bilayer organic LEDs

Organic structures consisting of two distinct layers (bilayer), a hole tran sport layer and an electron transport/emitter layer are compared to structu res using a bipolar transport and emitting layer (BTEL). Reverse bias and d ifferent duty cycle did not significantly affect reliability. The BTEL stru cture had significantly improved reliability compared to the bilayer struct ure. The relative change in device voltage was found to be linearly proport ional to the relative change in luminance and the constant of proportionali ty was a function of the contact. This constant of proportionality can be u sed as a figure of merit for voltage increase during operation. The BTEL st ructure also gives improved reliability at elevated temperature. (C) 1999 E lsevier Science S.A. All rights reserved.