High-efficiency organic electrophosphorescent diodes using 1,3,5-triazine electron transport materials

This paper reports on novel electron transport materials, 1,3,5-triazine derivatives (TRZ), which have been useful in high-efficiency electrophosphoreseent (EP) organic light-emitting diodes (OLEDs). We synthesized four 2,4,6-tris(diarylamino)-1,3,5-triazine derivatives (TRZ1-TRZ4) that had electron-donating substituents and examined their OLED characteristics. Of these, we found that TRZ 2, 3, and 4 function as a host for tris(2-phenylpyridine)iridium (Ir(ppy)(3)) and, in particular, 2,4,6-tris(carbazolo)-1,3,5-triazine (TRZ2) demonstrated a very high external electroluminescent (EL) quantum efficiency (eta(ext)) of similar to10.2 +/- 1.0% and an energy conversion efficiency (eta(energy)) of 14.0 +/- 2.0 lm/W. Detailed transient photoluminescent (PL) measurement revealed that the triplet energy level of TRZ2 (E(T1) 2.81 eV) is higher than that of conventional 4,4'-N,N'-dicarbazol-biphenyl (CBP) (E(T1) = 2.56 eV), suggesting that TRZ2 has excellent capabilities in confining Ir(ppy)(3) triplet excitons.