The performance of organic light emitting devices (OLEDs) is closely related to the electric field intensity and carrierdensity distribution in the organic layer.Based on the drift-diffusion theory for themotion of charge carriers

we considered the OLED structure consists of a single layerof luminescentor ganicmaterial sandwiched between twometallic electrodes

the contacts between themetallic electrodes and organicmaterial are ohmic.We adopted themethod of numerical calculation to study the potential

electric field intensity

carrier density and recombination rate in the organicmaterial.The results shown these:(1) when holes and electrons have the same mobility

the distribution of the potential

electric field

carrierdensity and recombination rate is symmetrical.This is because the in fluence of two differentcarriers injection is the same.Mostcarriers distribute near the electrodes and decrease very fast

the interface of metal/semiconductor contact is just like a carrier packet and the carrierdensity is very low in the middle of the device

so the electric fieldsnear the two contacts aremuch stronger than that in themiddle.(2)When themobility of holes and electronsdiffersgreatly

the highermobility carriers can notonly distribute near the injecting electrode butalso transmit to another electrode.However

the lowermobility carriers distri-butemainly near the injecting electrode.When themobility difference of electron and hole is small

the distri-bution of the carriers isbetween the above two cases.When the ratio of holemobility to electronmobility changes

the position of themaximum of the electric fieldmoves to the electrode from which the lowmobility carriers are in jected.