A cross-linkable triphenylamine derivative as a hole injection/transporting material in organic light-emitting diodes

Abstract

We have synthesized TPABZ, a new thermally cross-linkable triphenylamine derivative containing a benzoxazine functional group, for application in organic light-emitting diodes (OLEDs). We used differential scanning calorimetry, thermogravimetric analysis, UV-Vis spectroscopy, and cyclic voltammetry to investigate the thermal, physical, and electrochemical properties of TPABZ, which is readily polymerized, through ring-opening polymerization of its benzoxazine unit, upon heating at 220 degrees C for 30 min. The cured TPABZ (P-TPABZ) is suitable for use as a hole injection/transport material in OLEDs because it has an appropriate HOMO energy level (-5.16 eV) to form a stepwise energy ladder and a high LUMO energy level (-1.68 eV) with great potential for electron blocking. We fabricated multilayered OLEDs (ITO/TPABZ or P-TPABZ/NPB/Alq(3)/LiF/Al) through successive spin-coating and vacuum deposition processes; the device incorporating P-TPABZ exhibited good performance (EQE: 2.44%; LEmax: 8.42 cd A(-1); PEmax: 4.34 lm W-1).