Molecular design of hole transport material with various ionizationpotential for organic light-emitting diode applications

In this paper, we examine the effects of the properties for hole transport materials (HTM's) on the performance of organic light-emitting diodes (OLED's). The ionization potentials (I_p) of the HTM's could be estimated by the Hammett constant of the substituent. We have synthesized a series of HTM's with various I_p's, which are called FTPD's. The FTFD's have high glass transition temperature above 80°C, because of their fluorene structure. We fabricated double-layer OLED's with the FTPD's. The I_p's of the FTPD's affected the driving voltage, although they did not affect the quantum efficiency