Surface modification of TiO_2 by a self-assembly monolayer in inverted-type polymer light-emitting devices

摘要

A self-assembled monolayer, N-[3-(trimethoxysily)propyllethylenediamine (PEDA-TMS), is employed to modify a titanium dioxide (TiO_2) surface for tuning its conduction band to match the energy level of high-yellow phenyl-substituted poly(para-phenylenevinylene) copolymer (HY-PPV) for fabricating inverted-type polymer light-emitting diodes (1-PLEDs). Ultraviolet photoemission spectroscopy (UPS) and electron-dominated devices were used to investigate changes of the electron-injection barrier. A PEDA-TMS-modified device achieved much higher brightness (3148 cd/m~2) than that of the bare TiO_2 device (no luminescence). The air stability of the proposed device is highly improved by the use of stable electrodes and injection layers. These significant improvements make TiO_2 application to PPV-based PLEDs.