Organic light-emitting devices (OLED) based on new triphenylamine derivatives

In this paper, we reported the synthesis of two new triphenylamine derivatives: 1,4-bis[-E-4-(N,N-diphenylamino)styryl]naphthalene (Np-G1) and 2,8-bis[-E-4-(N,N-diphenylamino) styryl]dibenzothiophene (ST-G1) and investigated the electroluminescence characteristics of the three-layer devices with Np-G1 or ST-G1 as emitting layer. The results have shown that introduction electron-acceptor group, naphthalene, into triphenylamine units, Np-G1 with linear geometric conformation can lower its LUMO level obviously and resulting facilitate electron injection and transport for the device. Thus, the three-layer device (ITO/TCTA/Np-G1/BCP /Mg:Ag) improved the electroluminescence properties the best, presenting the brightness of ∼10,000 cd/m2 and current efficiency of ∼3.0 cd/A. On the other hand, ST-G1 with V-shaped conformation containing dibenzothiophene linked triphenylamine groups cannot effectively decreased its LUMO level. As a result, ST-G1 has little contribution to the carrier recombination within itself.