| Summary: | 碩士 === 國立成功大學 === 電機工程學系 === 89 === DCM2 is a red fluorescent dye which PL (photoluminescence) peak is 650nm. DCM2 mainly utilized to doping into a host material make device to emit strongly red light by Forest energy transfer. Due to the efficiency of energy transfer from a host to a dopant and the characteristic of interface, the emission behavior will be changed. In our investigation, we would discuss obviously the emissive behavior of organic electroluminescent device by doping red fluorescent dye in different layer.
In the experiment, we first doped DCM2 into electro-transporting layer (AlQ). Due to the well overlap of absorption of DCM2 and PL of AlQ, it is effective to transfer energy by Forest rule. Then we find that the purity is getting better by increasing concentration but the luminance decreases due to high-concentration quenching. Furthermore, in order to replace AlQ, we doped DCM2 into hole-transporting layer (NPB). It is found no matter how concentration we added the blue light of NPB still remained. Although, there is almostly complete energy transfer between DCM2 and NPB, but from our experiment the recombination area is limited near the interface (about 25A~50A) of structure of NPB/BCP/AlQ and a large number of excitons at the interface cannot transfer completely. It should be why both red and blue light exists in EL spectrum. Finally, we doped DCM2 into hole-blocking layer (BCP) and got a perfect complementary white light by the thickness of BCP is 300A and the concentration of DCM2 is 1%. When the states in BCP are sufficient to support holes by increasing concentration, we get a pure red light but the lightness also decreases by increasing of concentration.
Anyhow, to get a pure red light device is to doping DCM2 into electron-transporting layer.(AlQ) at the doping degree of 1%. The turn-on voltage of the red light device is 8V and the peak is 610nm. On the other hand, making white light device is doping DCM2 into hole-transporting layer (NPB) or hole-blocking layer (BCP). The doping degree of both devices is 1%. The turn-on voltage of doped HTL and doped HBL are 10V and 14V as well as CIE coordinates are (0.34,0.35) and (0.32,0.32) respectively.
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