In order to study the current roll-off in organic light-emitting diodes (OLEDs) under high luminance, the current density versus voltage (J-V) characteristics and the spectra of single-layer and bilayer devices pumped...
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In order to study the current roll-off in organic light-emitting diodes (OLEDs) under high luminance, the current density versus voltage (J-V) characteristics and the spectra of single-layer and bilayer devices pumped by sources in varied radiation intensities have been observed. The current densities in single-layer device decrease and the spectra shifte towards blue region, since the large amounts of excess anion radicals intensely absorb the emitted photons to cause the carrier density reduction. In order to balance the excess anion radicals, bilayer devices are constructed by inserting hole transport layers (HTLs) of four thicknesses in single-layer device. The current roll-off and spectral blue shift are reduced with the increase of the HTL thickness and decrease slightly when the thickness exceeds 50 nm. It is shown that inserting a hole transport layer of proper thickness is one of the methods to restrain the current roll-off.
Thermal interface materials (TIMs), including thermal conductive adhesives (TCAs), grease, phase change materials (PCMs) and thermal pads, are widely used in thermal management for electronics system. In this work, a ...
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Thermal interface materials (TIMs), including thermal conductive adhesives (TCAs), grease, phase change materials (PCMs) and thermal pads, are widely used in thermal management for electronics system. In this work, a bimodal thermal conductive adhesive (b-TCA) composed of epoxy matrix and silver fillers were developed. The silver fillers consist of silver flakes and silver particles. The specimens have been made with the same filler loading fraction, possessing different ratios of silver flake portion to silver particle one to study the filler geometry effects. The thermal conductivity in vertical and in-plane direction were tested, also the electrical resistance in in-plane direction has been measured. Meanwhile, the numerical simulation was carried out in addition to the experiment. An improved cubic cell model (CCM) was developed to calculate the effective thermal conductivity of the considered b-TCA. Both the experiment and the simulation show the anisotropic thermal conductive property in the b-TCA, but this anisotropy decreased with the increase of silver particle portion in the total filler. And the electrical conductivity also decreased with the increase of silver particles.
The effective automatic location and tracking of a person's lip has been proven to be very difficult in the field of computer vision. A lip segmentation approach is proposed based on wavelet multi-scale edge detec...
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The effective automatic location and tracking of a person's lip has been proven to be very difficult in the field of computer vision. A lip segmentation approach is proposed based on wavelet multi-scale edge detection across lip map. The developed algorithm exploits the spatial interactions between neighboring pixels through wavelet multi-scale edge detection across the lip map. The algorithm produces better segmentation automatically without the need to determine an optimum threshold for each lip image. It has indicated the developed algorithm with superior performance by comparing with some existing lip segmentation algorithms.
Based on red, green, blue multi-emitting layer, organic light-emitting devices (OLEDs) with different order of emission layer are fabricated. White OLEDs are realized based on the research of the influence of order an...
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Based on red, green, blue multi-emitting layer, organic light-emitting devices (OLEDs) with different order of emission layer are fabricated. White OLEDs are realized based on the research of the influence of order and thickness of different emission layers on the performances of devices. The saturated white OLED coming from a balance of different colors is realized by adjusting the thickness of the key emission layer. The color drift is tiny since the thickness of the key emission layer is very thin. The optimized white OLED has a current efficiency of 3.78 cd/A, and commission internationale d′Fclairage(CIE) coordinates of (x=0.345, y=0.323) at 200 mA/cm2. According to the theory of excitions generation and diffusion, the relationship between spectrum intensity and the thickness of every layer, the excitons diffusion length is discussed. The result of the theory analysis is in good agreement with the experiments.
The Wigner-Ville distribution （WVD） and the cross Wigner-Ville distribution （XWVD） have been shown to be efficient in the estimation of instantaneous frequency （IF）. But the statistical result of the IF estimati...
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The Wigner-Ville distribution （WVD） and the cross Wigner-Ville distribution （XWVD） have been shown to be efficient in the estimation of instantaneous frequency （IF）. But the statistical result of the IF estimation from XWVD peak is much better than using WVD peak. The reason is given from a statistical point of view. Theoretical studies show that XWVD of the analyzed signal can be estimated from XWVD of the noise-contaminated signal. The estimation is unbiased, and the variance is equal to that of noise. In this case, WVD cannot be estimated from W-VD of the noise-contaminated signal. Therefore, higher SNR is required when WVD is used to analyze signals.
Interpolation is the main bottleneck in AVS real-time high definition video encoder for its high memory bandwidth and large calculation complexity caused by the new coding features of variable block size and 4-tap fil...
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Gallium-doped zinc oxide (GZO) transparent conductive thin films were deposited on glass substrate by RF magnetron sputtering using a ceramic ZnO target with 10 wt. % Ga2O3 doped. The effects of substrate temperature ...
Gallium-doped zinc oxide (GZO) transparent conductive thin films were deposited on glass substrate by RF magnetron sputtering using a ceramic ZnO target with 10 wt. % Ga2O3 doped. The effects of substrate temperature on structural, electrical and optical properties of the films were investigated. X-ray diffraction (XRD) measurements indicated that GZO films were polycrystalline and strongly c-axis oriented. The surface roughness evaluated in terms of RRMS measured by atomic force microscope (AFM) was 1.8 nm for the smoothest surface obtained at 250 °C. The electrical resistivity decreases with increasing substrate temperature and the lowest resistivity obtained was 5.8×10-4 Ωcm at 350 °C. The average transmittance in the visible region was over 90%. The carrier concentration increased with substrate temperature increasing, and the highest mobility value was 22.1 cm2v-1s-1.
This paper proposed a novel approach to segment objects from the H.264 compressed video with moving background. At first, the noisy motion vectors are eliminated from the motion field by vector median filtering. Then ...
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An organic thin-film transistor (OTFT) device is investigated. Thermal grown SiO2layer is used as the OTFT gate dielectric;Copper phthalocyanine (CuPc) is used as an active layer. It is found that using silane couplin...
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An organic thin-film transistor (OTFT) device is investigated. Thermal grown SiO2layer is used as the OTFT gate dielectric;Copper phthalocyanine (CuPc) is used as an active layer. It is found that using silane coupling agents-octadecyltrichlorosilane (OTS) can reduce the surface energy of the SiO2gate dielectric and significantly improve device performance. This OTS/SiO2bilayer gate insulator configuration increases the field-effect mobility by 2.5 times, reduces the threshold voltage by 3 V, and improves the on/off ratio from 103 to 104. We adopte MoO3to modify Al as drain and source electrodes with double-layer structure at the same time. The device with MoO3/Al electrode has similar Ids compared with the device with Au electrode at same gate voltage. Our results indicate that using double-layer of electrode and double-layer of insulator is an effective way to improve OTFT performance.
An organic thin-film transistor (OTFT) with an OTS/SiO2 bilayer gate insulator and a MoO3/Al electrode configuration between gate insulator and source/drain electrodes has been investigated. A thermally grown SiO2 lay...
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An organic thin-film transistor (OTFT) with an OTS/SiO2 bilayer gate insulator and a MoO3/Al electrode configuration between gate insulator and source/drain electrodes has been investigated. A thermally grown SiO2 layer is used as the OTFT gate dielectric and copper phthalocyanine (CuPc) is used as an active layer. This 0TS/SiO2 bilayer gate insulator configuration increases the field-effect mobility, reduces the threshold voltage, and improves the on/off ratio simultaneously. The device with a MoO3/Al electrode has shown similar Ids compared to the device with an Au electrode at the same gate voltage. Our results indicate that using a double-layer of electrodes and a double-layer of insulators is an effective way to improve OTFT performance.
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