Organic light-emitting devices based on vacuum-deposited poly(p-phenylene)thin film

Organic Light-emitting device with poly(p-phenylene) (PPP) is prepared by v acuum deposition with various heating rates. The structure, morphology, pho toluminescence (PL), electroluminescence (EL), and current (I)-voltage (V)- EL characteristics have been studied by IR spectroscopy, atomic force micro scopy (AFM) and spectrofluorophotometer. The LR spectrum gave an evidence t hat the vacuum-deposited PPP (vd-PPP) chain involves 8-9 p-phenylene rings, which is known to be an effective conjugation length. The onset of the EL occurs at the electric field of about 7 X 10(7) V/m. I-V dependence fits ve ry well with the Fowler-Nordheim (FN) tunneling formula. The results sugges t that charge carrier injection is a tunneling process through an energy ba rrier of about 0.6-0.8 eV in ITO/PPP/AI devices. (C) 2000 Elsevier Science S.A. All rights reserved.