We investigated the interfacial electronic structures of indium tin oxide (ITO)/molybdenum trioxide (MoO3)/N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) using in situ ultraviolet and x-ray photoemission spectroscopy to understand the origin of hole injection improvements in organic light-emitting devices (OLEDs). Inserting a MoO3 layer between ITO and NPB, the hole injection barrier was remarkably reduced. Moreover, a gap state in the band gap of NPB was found which assisted the Ohmic hole injection at the interface. The hole injection barrier lowering and Ohmic injection explain why the OLED in combination with MoO3 showed improved performance.
We report on the optical and luminescence properties of pentacene films deposited on n-Si by thermal evaporation at room temperature, 40, 60, 80, and 120 °C. Ellipsometric spectra of the films deposited at room temperature and 60 °C exhibited a main absorption peak at 1.82 eV and additional weak features at higher energy levels. Photoluminescence spectra taken at room temperature revealed band-to-exciton and band-to-acceptor transitions at 1.7 and 1.76 eV, respectively. An electroluminescence band was also observed near 1.65 eV under a forward bias from p-pentacene/n-Si diodes which show strong rectifying behavior.
Solution-processed dye-sensitized ZnO phototransistors with extremely high photoresponsivity J. Appl. Phys. 112, 074507 (2012) Direct electrostatic toner marking with poly(3,4-ethylenedioxythiophene)polystyrenesulfonate bilayer devices J. Appl. Phys. 112, 074506 (2012) Modeling the effect of top gate voltage on the threshold of a double gate organic field effect transistor J. Appl. Phys. 112, 073704 (2012) Electron transporting water-gated thin film transistorsWe studied systematically the influence of in situ postannealing treatment of ultrahigh vacuum grown polycrystalline pentacene thin film transistor. The gradual grain growth with the elimination of defects and misoriented crystallites is confirmed in x-ray diffraction ͑XRD͒ data and the atomic force microscopy image as the annealing temperature increases. The XRD data reveal that the pentacene molecules are packed parallel to each other in an upright position with a tilting angle of 15.5°. The postannealing results in the enhanced field effect mobility of pentacene organic thin film transistors increases from 0.19Ϯ0.04 to 0.49Ϯ0.05 cm 2 /V s after annealing at 90°C. We suggest that the abnormally small on/off current ratio (ϳ10 3 ) due to the large leakage current is attributed to the conduction via impurity levels originated from the structural isomers of pentacene.
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