Schottky energy barriers and charge injection in metal/Alq/metal structures

We present internal photoemission, photocurrent versus bias voltage, and current–voltage measurements of metal/tris-(8-hydroxyquinoline) aluminum [Alq]/metal structures. Internal photoemission and photocurrent versus bias measurements were used to determine metal/Alq Schottky energy barriers for a range of contact metals with work functions from 2.7 eV (Sm) to 5.6 eV (Pt). The electron Schottky barrier for low work-function metals ( about 3.6 eV) the ideal Schottky model is generally accurate. A previously established device model was used to describe the current–voltage characteristics using the measured Schottky barriers. The results imply comparable electron and hole mobilities of about 2×10−5 cm2/V s at an electric field of 106 V/cm.