We fabricated a hybrid WOLED based on Bepp2 as the blue fluorescent emitter with a structure as shown in Fig. 7[61]. In the device TCTA:Bepp2 is still used as the spacer layer, Ir(MDQ)2(acac) doped into TCTA as the red phosphorescent EML, and Ir(ppy)2(acac) doped into Bepp2 as the blue/green EML. To get both blue fluorescent and green phosphorescent emissions from Bepp2:Ir(ppy)2(acac), our strategy is to decrease the doping concentration of Ir(ppy)2(acac). It is known that the diffusion length of a singlet (RS) is about 3 nm, and that of a triplet (RT) can be over 100 nm. Certain fluorophors can find phosphors only within the radius between Rs and RT when decreasing the phosphorescent dopant to an appropriate concentration. In this case, the triplet excitons transfer from fluorophor to phosphor while the singlet excitons are confined and used for fluorescence, as illustrated in Fig. 8. We doped 0.3% Ir(ppy)2(acac) in Bepp2 and obtained a primary color emission in the hybrid WOLED. The efficiencies and spectra are shown in Fig. 9. The power efficiency and EQE were 23.0 lm/W and 11.9% at 1000 cd/m2, respectively. The spectra in this hybrid WOLED were very stable, and the CRI reached as high as 90 and the CIE stayed at (0.42, 0.44).
We fabricated a hybrid WOLED based on Bepp2 as the blue fluorescent emitter with a structure as shown in Fig. 7[61]. In the device TCTA:Bepp2 is still used as the spacer layer, Ir(MDQ)2(acac) doped into TCTA as the red phosphorescent EML, and Ir(ppy)2(acac) doped into Bepp2 as the blue/green EML. To get both blue fluorescent and green phosphorescent emissions from Bepp2:Ir(ppy)2(acac), our strategy is to decrease the doping concentration of Ir(ppy)2(acac). It is known that the diffusion length of a singlet (RS) is about 3 nm, and that of a triplet (RT) can be over 100 nm. Certain fluorophors can find phosphors only within the radius between Rs and RT when decreasing the phosphorescent dopant to an appropriate concentration. In this case, the triplet excitons transfer from fluorophor to phosphor while the singlet excitons are confined and used for fluorescence, as illustrated in Fig. 8. We doped 0.3% Ir(ppy)2(acac) in Bepp2 and obtained a primary color emission in the hybrid WOLED. The efficiencies and spectra are shown in Fig. 9. The power efficiency and EQE were 23.0 lm/W and 11.9% at 1000 cd/m2, respectively. The spectra in this hybrid WOLED were very stable, and the CRI reached as high as 90 and the CIE stayed at (0.42, 0.44).
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