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In this study, we present the comparison of device performance measurements for organic light emitting diodes using a spectroradiometer through the viewing angle and integrating sphere, widely used for device measurements. The mean calculation method using these results was applied to convert the spectroradiometer (under different viewing angles) data to match with the integrating sphere measurements. The conversion of the spectroradiometer based quantum efficiency and electroluminescence data from all different angular emission patterns was similar to that of the integrating sphere data within a reasonable range of deviation. As such, it is possible to reduce the recurring costs and required time between these two measurement techniques by bypassing the integrating sphere measurement. [ABSTRACT FROM AUTHOR]

The effects of tetrafluoromethane (CF4) plasma treatment of indium-tin-oxide (ITO) anode on indium diffusion into a poly(3,4-ethylene dioxythiophene):poly(styrene sulphonate) (PEDOT:PSS) layer were studied. Auger electron spectroscopy (AES) depth profile showed that 0.2 at. % indium was present in the PEDOT:PSS layer when ITO was not plasma treated. The plasma treatment of ITO increased the indium concentration to ∼6 at. %. The increase in indium can be explained by an oxygen deficiency in the CF4 plasma treated ITO. The presence of indium in the PEDOT:PSS layer showed a correlation with performance degradation of polymer light-emitting diodes. [ABSTRACT FROM AUTHOR]

This communication reports on the fabrication of low operating voltage pentacene thin-film transistors with high-k gate dielectrics by ion beam assisted deposition (IBAD). These densely packed dielectric layers by IBAD show a much lower level of leakage current than those created by e-beam evaporation. These results, from the fact that those thin films deposited with low adatom mobility, have an open structure, consisting of spherical grains with pores in between, that acts as a significant path for leakage current. By contrast, our results demonstrate the potential to limit this leakage. The field effect mobility, on/off current ratio, and subthreshold slope obtained from pentacene thin-film transistors (TFTs) were 1.14 cm2/V s, 105, and 0.41 V/dec, respectively. Thus, the high-k gate dielectrics obtained by IBAD show promise in realizing low leakage current, low voltage, and high mobility pentacene TFTs. [ABSTRACT FROM AUTHOR]

Silver nanowires (AgNWs) have become an efficient electrode candidate for stretchable electronics. We report the effects of directional stretching in microprism-mediated AgNW stretchable electrodes on polyurethane (PU) substrates. The wavy substrate is fabricated using a customized microprism on polyethylene terephthalate. AgNWs on stretchable PU substrates show stable normalized resistance up to 35% strain under parallel uniaxial stretching. This performance is much better than AgNWs on bare PU substrate or on wavy PU under perpendicular stretching, which can only sustain 10%-15% strain before significant increase in normalized resistance. Finite element simulations were conducted to reveal the strain distribution and variation in the AgNW electrodes on both bare and wavy PU substrates when stretched along parallel and perpendicular directions. Comparing to AgNW electrodes on bare PU and on wavy PU under perpendicular stretching, the wavy PU surface relief features can effectively alleviate the strain in the AgNW network when stretched along parallel direction, leading to better performance. [ABSTRACT FROM AUTHOR]

The authors have developed a semitransparent, multilayered cathode of indium tin oxide (ITO)/Ag/tungsten oxide (WO3) for transparent organic light-emitting diodes. The device showed a weak negative differential resistance (NDR), until the operating voltage of 8 V was reached. NDR was due to the resonant tunneling by both the quantum barrier and quantum well. The silver oxide (Ag2O) on the Ag metal was confirmed by x-ray photoelectron spectroscopy, and the energy levels of Ag2O were quantized due to the quantum size effect and this produced the resonant tunneling channels. The device using ITO/Ag/WO3 with a LiF/Al bilayer was superior to those devices which only used ITO or WO3, mainly because the out coupling was enhanced by employing a WO3 material, which is much more transparent than ITO. [ABSTRACT FROM AUTHOR]

A semitransparent cathode of indium tin oxide (ITO)/Ag/ITO was developed as a resonant tunneling double barrier structure for transparent organic light-emitting diodes. A weak negative differential resistance was observed in devices using a 100 nm thick ITO/Ag/ITO layer as a cathode in combination with a thin LiF/Al layer. The current injection of devices was dominated by resonant tunneling, which induced no luminance at low voltage. This was achieved by employing an e-beam evaporated ITO/Ag/ITO cathode due to the double quantum barriers of ITO and the quantum well of Ag. The authors also applied the multilayer cathode to small molecule devices, which showed the same resonant tunneling currents. [ABSTRACT FROM AUTHOR]

Pentacene organic thin film transistors (OTFTs) with low-k and high-k hybrid gate dielectrics by CF4 plasma treatment exhibited excellent device performance with field effect mobilities (maximum 1.41 cm2/V s), a low threshold voltage of +1 V, and on/off current ratios of 105 at -5 V gate bias. After CF4 plasma treatment, fluorine atoms diffuse into the interior low-k polymer and eliminate ionic impurities which reduce the leakage current density and overall pentacene initial growth on the superhydrophobic surface is significantly improved. It seems apparent that proper surface treatment is desirable for higher quality pentacene film and improving the performance of OTFTs. [ABSTRACT FROM AUTHOR]