Estimation of the mean emission zone in phosphorescent organic light-emitting diodes with a thin emitting layer

We presented an approach to estimate the emission zone (EZ) positions in high efficiency phosphorescent OLEDs with a thin emitting layer. Two devices with different distances between the emitting layer and the cathode (i.e. they are optically different), but exhibiting same current density-voltage characteristics (i.e. they are electrically the same) were used for this purpose. Mean EZ positions in the OLEDs were extracted from the comparison of the experimental luminous intensity ratio vs. the current density with the calculated intensity ratio vs. the EZ position. The validity of the approach was confirmed by the agreement between calculated and experimental spectral changes. (C) 2010 Optical Society of America