Interface electronic structure of the organic light-emitting devices: Photoemission and x-ray absorption studies of Al∕KF∕Alq3 interface

The chemistry of organic light-emitting diode interface composed of KF sandwiched between the Al and Alq3 was investigated using near-edge x-ray absorption fine structure (NEXAFS) as well as x-ray and ultraviolet photoelectron spectroscopy techniques. At the earliest stages of KF deposition on Alq3, changes in F K-edge NEXAFS spectra indicated a strong chemical reaction, which is responsible for the dipole layer formation seen in valence-band spectra. For Al deposition on KF∕Alq3, the reactions inferred from observed spectral changes are not consistent with the commonly believed KF dissociation and AlF3 formation scenarios.