Comparative studies on EL performances of the OLEDs prepared by PVD, NCBD and ICBD methods

Organic light emitting diodes (OLEDs) with the structure of indium-tin-oxid e glass/spin-coated poly[2-(N-carbazolyl)-5-(2-ethyl-hexyloxy)-1,4-phenylen evinylene]/8-hydroquinoline aluminum/Li:Al [ITO-glass/CzEH-PPV/Alq(3)/Li:Al ] have been fabricated by applying three deposition methods: physical vapor deposition (PVD), neutral and ionized cluster beam depositions (NCBD and I CED). Atomic force microscopy (AFM) measurements show that the weakly bound and highly directional cluster beam is effective in producing uniform flat film surfaces. Photo- and electro-luminescence (PL, EL) spectra demonstrat e that the NCBD and PVD methods produce more efficient EL devices and the i ntroduction of neutral buffer layer to the ICED devices enhances the perfor mances. DCM-doped devices show color-tuning capability and higher external quantum efficiency (EQE) compared to undoped devices.