Hsin-Hsuan Huang

Electrical bistability in hybrid ZnO nanorod/polymethylmethacrylate heterostructures

A hybrid resistance switching device consisting of ZnO nanorods embedded in an insulating polymethylmethacrylate (PMMA) heterostructure sandwiched between a transparent conductive film and an Al electrode is proposed. The current-voltage characteristics of the device are discussed in terms of the formation and rupture of its conductive filaments. The hybrid device shows stable electrical bistable behaviors after more than 200 resistance-switching cycles. The hybrid ZnO nanorod/PMMA device presented in this work has potential applications in the field of bistable random access memory devices.

How the surface energy of ultra-thin CuF2 film as anode buffer layer affect the organic light-emitting devices?

The effect of surface energy on organic light-emitting device performance was demonstrated by depositing an ultra-thin CuF2 buffer layer on indium tin oxide (ITO) substrates, followed by ultraviolet (UV)-ozone treatment. An optimal thickness UV-ozone treated CuF2 (4 nm)/ITO anode significantly improved device performance. Work function estimates from X-ray photoelectron measurements suggested that both pristine and UV-ozone treated CuF2/ITO anodes had no hole injection barrier. Measurements of energy band, surface energy and surface polarity indicated device improvement came from the simultaneous increase in work function and surface energy of ITO by adding treated CuF2 film between ITO and the hole-transporting layer.

Improved Hole-Injection and Power Efficiency of Organic Light-Emitting Diodes Using an Ultrathin Li-Doped ZnO Buffer Layer

We report on the advantages of an anode buffer layer of Li-doped ZnO (LZO) on the electro-optical properties of organic light-emitting diodes (OLEDs). LZO layers with different thicknesses were prepared by thermally evaporating the LZO powders and then treating them with ultraviolet (UV) ozone exposure. The turn-on voltage of OLEDs decreased from 4 V (4.2 cd/m 2 ) to 3 V (5.1 cd/m 2 ), the maximum luminance value increased from 16780 to 28150 cd/m 2 and the power efficiency increased from 2.74 to 5.63 Im/W when a 1 nm thick LZO layer was inserted between indium-tin oxide (ITO) anodes and β-naphthylphenylbiphenyl diamine hole-transporting layers. X-ray and ultraviolet photoelectron spectroscopy were performed to show that the formation of the LZO layer and the work function increased by 0.64 eV when the LZO/ITO layer was treated by UV-ozone for 20 min. The surface of the LZO/ITO film became smoother after the UV-ozone treatment. Thus, the hole-injection energy barrier was lowered by inserting an LZO buffer layer, resulting in the decrease of the turn-on voltage and the increase of the power efficiency in OLEDs.