Graphene film can be used as transparent electrodes in display and optoelectronic applications. However, achieving residue free graphene film pixel arrays with geometrical precision on large area has been a difficult challenge. By utilizing the liquid bridging concept, we realized photolithographic patterning of graphene film with dimensional correctness and absence of surface contaminant. On a glass substrate of 100 × 100 mm2 size, we demonstrate our patterning method to fabricate an addressable two-color OLED module of which graphene film pixel size is 170 × 300 µm2. Our results strongly suggest graphene film as a serviceable component in commercial display products. The flexible and foldable display applications are expected to be main beneficiaries of our method.
Area-selective external light extraction films based on wrinkle structured films were applied to large transparent organic light-emitting diodes (TOLEDs) with auxiliary metal buses. To be specific, on the external surface of the glass, we selectively formed a wrinkle structured film, which was aligned to the auxiliary metal electrodes. The wrinkle-structured film was patterned using a photo-mask and UV curing, which has the same shape of the auxiliary metal electrodes. With this area-selective film, it was possible to enhance the external quantum efficiencies of the bottom and top emissions TOLEDs by 15.7% and 15.1%, respectively, without significant loss in transmittance. Widened angular luminance distributions were also achieved in both emissions directions.
We chose pentacene as a hole injection layer (HIL) to fabricate the high performance blue fluorescent organic lightemitting devices (OLEDs). We found that the carrier mobility of the pentacene thin films could be efficiently improved after a critical annealing at temperature 120 • C. Then we performed the tests of scanning electron microscopy, atomic force microscopy, and Kelvin probe to explore the effect of annealing on the pentacene films. The pentacene film exhibited a more crystalline form with better continuities and smoothness after annealing. The optimal device with 120 • C annealed pentacene film and n-doped electron transport layer (ETL) presents a low turn-on voltage of 2.6 V and a highest luminance of 134800 cd/m 2 at 12 V, which are reduced by 26% and improved by 50% compared with those of the control device.
This paper presents the design and implementation of a single-loop three-order switched-capacitor sigma-delta modulator(SDM) with a standard 0.18um CMOS technology. A current optimization technique is utilized in proposed design to reduce the power of operational transconductance amplifier(OTA).Using a chain of Integrators with weighted feed-forward summation(CIFF) structure and optimized single-stage class-A OTA with positive feed-back to minimize the power consumption. The SDM has been presented with an over-sampling ratio of 128,clock frequency 6.144MHz,24kHz band- width, and achieves a peak SNR of 100dB,103dB dynamic range. The whole circuits consume 2.87mW from a single 1.8V supply voltage.
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