An organic light emitting diode is an electric diode that emits light through electric current by applied voltage. Tang et al. reported an organic light emitting diode having a good characteristic in a treatise [Applied Physics Letters 51, p. 913, 1987]. Further, an organic light emitting diode using a polymer material while using a structure of the organic light emitting diode disclosed in the treatise has also been developed.
The key point of the related art is to allow different organic material layers to share roles for performing processes in which the organic light emitting diode may emit light, such as charge injection, charge transport, formation of optical exciton and generation of light. Therefore, recently, as illustrated in FIG. 1, an organic light emitting diode comprising a first electrode 2, a hole injection layer 5, a hole transporting layer 6, a light emitting layer 7, an electron transporting layer 8 and a second electrode 4 or an organic light emitting diode having a segmented structure constituted by multiple layers has been used.
The organic light emitting diode is classified into a fluorescent OLED and a phosphorescent OLED (PhOLED) according to the emission type of light. In the PhOLED, light may be emitted from both singlet and triplet excitons. Therefore, the internal quantum efficiency reaches theoretically 100%, but in an actual diode, there is a problem in that light emission efficiency is significantly reduced due to injection loss of carriers, formation of non-luminescent excitons, triplet-triplet annihilation and the like.
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