Charge injection spectroscopy of Alq3 thin films deposited on bare and LiF-modified metal substrates

The local electronic properties of an electron-transfer material Alq(3) [tris(8-quinolinolate) aluminium] at the electrode interface of various metals, including base metal aluminium, were investigated using charge injection spectroscopy. We found that electron (hole) polaron energies vary strongly from one measured point to the other, but their energy distribution curves have significant peaks. We also found that the peak energy values changed, depending on the metal work functions. In addition, researchers think that the polaron energies at metal interfaces are lower than those in bulk. LiF-modified electrodes were also examined. On examination, we found that the electron polaron energies at the interface substantially decrease as the LiF thickness increases in the region of <0.5 nm. This result is consistent with the improved device efficiency of organic light emitting diodes, which have an optimal LiF thickness of 0.5 nm. (c) 2005 Elsevier B.V. All rights reserved.