Active matrix organic-light-emitting-diode (AM OLED) panels, driven by organic thin-film transistors (OTFT), have been successfully fabricated on a flexible plastic substrate. The pixel circuit consists of two bottom-contact pentacene OTFTs working as switching and driving transistors. The panel has 16 × 16 pixels, each of which have an OLED using a phosphorescent material with an emission efficiency of 30 cd/A. A tantalum oxide (Ta 2 O 5 ) film with a dielectric constant of 24, prepared by the anodization of Tantalum (Ta), was used as the gate insulator of the OTFTs. The passivation layer on the OTFTs was formed by a layer of silicon dioxide (SiO 2 ) and two layers of polyvinyl alcohol. Using OTFTs with a Ta 2 O 5 gate insulator, the authors have realized a flexible active matrix OLED panel driven with a low voltage of −12 V. Index Terms-Flexible, organic light emitting diode (OLED), organic thin-film transistor (OTFT), plastic.

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Efficient electrophosphorescent polymer light-emitting devices have been developed using a Cs/Al cathode. The materials used were a molecularly doped poly(9-vinylcarbazole)-emissive layer with electrophosphorescent complexes: bis[2-(2′-benzothienyl)-pyridinato-N,C3′](acetylacetonate)Ir(III) as a red emitter, fac-tris(2-phenylpyridyl)Ir(III) as a green emitter, and bis[(4,6-difluorophenyl)-pyridinato-N,C2](picolinato)Ir(III) as a blue emitter. The red, green, and blue electrophosphorescent emitting devices exhibited efficient emissions of 4, 31, and 14 cd/A, respectively. An inspection of secondary ion mass spectroscopy (SIMS) profiles confirmed that Cs diffuses into both Al and the emissive layer. Also, a Cs concentration of approximately 1 atomic% was estimated to be present at the interface from x-ray photoelectron spectroscopy (XPS) profiles.

The band alignment at the interface between Pt and O-terminated ZnO(0001) was investigated by depositing Pt films on ZnO using X-ray photoelectron spectroscopy and ultra violet photoelectron spectroscopy in an ultrahigh vacuum system. Angle-resolved X-ray photoelectron spectroscopy measurement showed the band was bent down by 0.06 eV at the ZnO(0001) surface. The binding energy of Zn 2p doublet shifted toward higher values by 0.37 eV when Pt was deposited on ZnO(0001). The work function of ZnO(0001) was 4.08 eV and the valence band maximum measured by UPS on the clean ZnO(0001) surface was 2.82 eV. As a result, the Schottky barrier height of Pt/ZnO(0001) was 0.72 eV in this experiment.

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