Browsing by Author "Wang, C. -L."

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A novel lens cap designed for the RGB LEDs installed in an ultra-thin and directly lit backlight unit of large-sized LCD TVs
(2008-02-01)
Chao, Paul C-P.
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Shen, C. -Y.
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Chiu, C. -W.
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Huang, J. -S.
;
Kao, Y. -Y.
The objective of this study is to design a novel cone-shaped lens cap on LEDs in order to achieve high optical efficiency in an ultra-thin directly lit RGB LED backlight unit (BLU) for large-sized LCD TVs. The use of the novel lens cap could play the role of a diffuser, a low light-efficiency component in a BLU, in order to gain higher efficiency and simultaneously provide satisfactory uniformity in light distribution. The novel cone-shaped lens is coated with aluminum on the outside surface of the cone for mirroring effects to reflect most of the LED emitted light horizontally and then reflect the light at the BLU boundaries, and then, finally to the output plane. In this way, bright spots on the output plane of the BLU can be avoided, leading to increased uniformity. Simulations were conducted to design and optimize varied aspects of the designed lens and BLU, including the cone angle of the proposed lens and the LED spacing (pitch). To further achieve color balance, a known Genetic Algorithm is used to search for the optimal angular placement of each RGB LED, resulting in better color balance. Finally, a prototype BLU for large-sized 37-in. LCD TVs with the proposed lens was built to verify the expected performance.
Enhancing the Solubility of n-Type Diketopyrrolopyrrole-Dicyanovinyl Molecules with Hybrid Siloxane Group for Solution-Processable Organic Field-Effect Transistor
(2019-01-01)
Prakoso, S. P.
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Ciou, G. -T.
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Lin, H. -Y.
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Peng, W. -C.
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Sie, J. -H.
Diketopyrrolopyrrole (DPP) organic dye is well-known to have poor solubility in most common organic solvents. In general, flexible alkyl chain is used to enhance the solubility of conjugated small molecules by disrupting the attraction between molecules. In this study, we have integrated hybrid organic-inorganic siloxane group as a solubilizing agent on DPP molecule carrying dicyanovinyl (DCV) as an electron-withdrawing group. UV-Vis absorption spectra were collected to evaluate the optical properties of these compounds. The electrical performances of these organic semiconductors were examined by fabricating into transistor device with them as active channel layer in the bottom gate staggered configuration. Furthermore, the molecular packing in thin films from this series was investigated by 2D grazing incident x-ray diffraction (GIXD) in relationship with device performances. It is shown that the siloxane group at the side chain of DPP effectively enhances the solubility of this molecule compared to DPP molecule with branched alkyl chain from previous study. A better solubility allows for device fabrication by solution process yet improves crystallinity of organic films and thus its electrical device performance.