Molecular design of hole transport material with various ionization potential 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