This paper reports the synthesis of well-aligned copper nanowires using an electrochemical deposition template technique. The electrical properties of copper nanowire arrays synthesized within vertical pores of alumina template were measured using a current-sensing atomic force microscope (AFM), with bias voltage applied between the AFM tip and the gold back-electrode. Nonlinear current-voltage (I-V) characteristics of copper nanowire arrays are observed; this is attributed to the impurities near the wire-lead contact region. These vertical copper nanowire arrays are suitable for use in fabricating nanoelectronic devices.
A high-contrast organic light-emitting diode (OLED) structure is presented. Because of poor contrast of conventional OLED resulting from high reflective metal cathode, the hybrid cathode structure was developed for low reflectivity. It consists the semitransparent cathode layers, passivation layers and a thick light-absorbing film. By optical reflectivity measurement and OLED electrical characterization tests for both OLED with the hybrid cathode and conventional OLED, it was found that the spectrum reflectance of OLED with hybrid cathode is among 8%-12%, about eight times lower than the conventional one when the two types of devices have similar turn-on voltages and current-voltage characteristics. The hybrid cathode for the high-contrast OLED is easily fabricated and its optical reflectance is slightly dependent on wavelength.
We have fabricated one kind of organic photocoupler with organic light-emitting diode as the input unit and pentacene photoresistor as the output unit. The wavelength of the emitting light was 522nm. The output current of the photocoupler linearly increased with its input current and the ratio of the transfer current density reached 3. When the output voltages were 60V, the ratio of the maximum output current to the minimum output current was 150. The breakdown voltage between the input unit and the output unit was more than 10kV and the response time of the device was about 6.5s. We believe this kind of device is promising in the full organic optoelectronic integrated circuits.
Tandem organic light emitting diodes (OLEDs) are ideal for lighting applications due to their low working current density at high brightness. In this work, we have studied an efficient electron transporting layer of KBH(4) doped 9,10-bis(3-(pyridin-3-yl)phenyl)anthracene (DPyPA) which is located adjacent to charge generation layer of MoO(3)/NPB. The excellent transporting property of the DPyPA:KBH(4) layer helps the tandem OLED to achieve a lower voltage than the tandem device with the widely used tris-(8-hydroxyquinoline)aluminum:Li. For the tandem white OLED with a fluorescent blue unit and a phosphorescent yellow unit, we've achieved a high current efficiency of 75 cd/A, which can be further improved to 120 cd/A by attaching a diffuser layer.
In order to accurately acquire the life time information for the organic light emitting diode (OLED), an experiment based on the normal stress life test was carried out to gain the data for the luminance degradation tests. The luminance degradation model of OLED was established based on the Weibull function and the least square method. Combined with luminance degradation data, Weibull parameters were estimated, the qualitative and the quantitative relationship between the initial luminance and the OLED life was obtained, and the life estimation of the product was achieved. Numerical results show that the test scheme is feasible, the luminance degradation model proves to be reliable for the OLED life estimation, and the fitting accuracy is very high by comparison with the test data fluctuation. Moreover, the real life time of the OLED is measured, which can verify the validity of the assumptions used in accelerated life test methods and provide manufacturers and customers with significant guidelines.
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