Electrical and optical studies of the organic thin film devices produced by cluster beam deposition methods

The neutral and ionized cluster beam deposition (NCBD and ICBD) methods have been applied to fabricate the new double-layer organic light emitting devices (OLEDs) with the structure of indium-tin-oxide (ITO)-coated glass/spin-coated poly[2-(N-carbazolyl)-5-(2-ethyl-hexyloxy)-1,4-phenylenevinylene] (CzEH-PPV)/8-hydroxyquinoline aluminum (Alq₃)/Li:Al. The surface morphology profiles measured by atomic force microscopy (AFM) showed that the cluster beam deposition methods are efficient in producing uniform and smooth film surfaces. Photo- and electro-luminescence (PL, EL) spectroscopies demonstrated that while the new hole transporting medium CzEH-PPV is susceptible to the bombardment of energetic ionized beam, the introduction of the neutral buffer layer significantly improves the device characteristics, i.e., lower threshold and turn-on voltages and higher external quantum efficiency (EQE). In addition, the effect of doping of highly fluorescent dye (DCM) into Alq₃ layer showed a complete energy transfer, color-tuning capability and higher EQE compared to the undoped devices.