Numerical Study on Organic Light Emitting Diodes with Distributed Bragg Reflector

In this paper, we report a theoretical study on the electronic-optical properties of the organic light emitting diodes (OLEDs) devices having a multilayer structure which consists of N,N'- bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine (TPD) as a hole transport layer (HTL) and tris(8-hydroxyquinolinato)aluminum (Alq3) as an electron transport layer (ETL). We investigated the angular dependence of the light density of emission as well as CIE chromaticity for devices with and without a distributed Bragg reflector (DBR) between the ITO and the glass wherein the DBR comprise two species of materials with different refractive indices. Our simulation revealed that the insertion of the bottom mirror plays a critical role for the improvement of in the emission efficiency of 17% and the sharper emission characteristics. We found out that the chromaticity as well as the viewing angle improved with the presence of the bottom mirror.