Investigation of the spectra of phosphorescent organic light-emitting devices in relation to emission zone

The dependence of the electroluminescent spectra on the emission zone of blue electrophosphorscent light emitting diodes (PHOLEDs) was investigated. The light emission of a PHOLED was tuned from blue to greenish blue by adjusting the position of the emission zone in the PHOLED. Experimental results agreed well with the numerical simulation based on the effect of the wide-angle optical interference by the metal cathode. The comparison of the numerical results and the electroluminescent spectra of the PHOLED was then extended to serve as the basis of another method to determine the location of the emission zones of PHOLEDs.