Browsing by Author "Han, H. V."

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A HIGHLY EFFICIENT HYBRID CDS-GAAS SOLAR CELL
(2012)
Chen, H. C.
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Lin, C. C.
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Tsai, Y. L.
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Han, H. V.
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Yu, Peichen
A novel design of hybrid solar cell combining traditional GaAs-based solar cell with colloidal CdS quantum dots (ODs) is demonstrated. By applying CdS ODs on the surface of GaAs device, we can obtain an effective antireflection coating at long wavelength. Moreover, due to its strong absorption at ultraviolet range and efficient light emission at blue photon, CdS quantum dots can down-convert the high-energy UV photons into visible ones, which are more easily to be collected in GaAs solar cell. The short circuit current and power conversion efficiency of this new device increases by 21% and 18.9%, respectively, when we compare them to the uncoated GaAs solar cell. An increase of the surface photoconductivity was also detected due to UV presence, and the fill factor of the CdS ODs solar cell can be improved accordingly.
Design of Highly Absorption Structure by Flatted ITO Patterned Substrate for Thin Film a-Si Solar Cells
(2012)
Han, H. V.
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Shih, H. S.
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Chen, H. C.
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Tsai, Y. L.
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Yu, P. C.
The patterned substrate is a flatted structure which composed with two materials to enhance the absorption of a-Si solar cell. We optimized this structure by simulation method and find it has good omnidirectional antireflection effect. (C) 2012 Optical Society of America
Enhance current density and light trapping effect in a-Si thin film solar cells by flexible textured PDMS film
(2013)
Han, H. V.
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Chen, H. C.
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Tsai, Y. L.
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Lin, C. C.
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Kuo, H. C.
The light trapping effect of a textured polydimethylsiloxane (PDMS) film on the suppression of surface reflection in a-Si:H solar cell is investigated. The angular dependence of scattered light from this PDMS film was measured and a symmetric scattering intensity peak was found at +/- 20(0). The enhancement of power conversion efficiency in the a-Si:H solar cell with textured PDMS film can reach 16.37% compared to the a-Si:H solar cells without textured PDMS film. This improvement is mainly attributed to the enhanced efficiencies of light trapping and scattering. Such a design concept and fabrication process can be widely adapted to a variety of thin film solar cells.
Enhancement of Light Harvesting and Power Conversion Efficiency in GaAs solar cells using flexible textured PDMS film
(2013-01-01)
Han, H. V.
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Chen, H. C.
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Lin, C. C.
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Tsai, Y. L.
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Yeh, Y. L.
Light trapping of textured polydimethylsiloxane films for antireflection is investigated. The efficiency of GaAs solar cell with textured PDMS film reach 28% enhancement. Numerical analysis successfully rebuilds the surface profile close to the real situation. (C) 2013 Optical Society of America
Excellent Color Rendering Index Quantum Dots White Light-Emitting Diode with Distributed Bragg Reflector Structure
(2014)
Chen, K. J.
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Lin, B. C.
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Han, H. V.
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Lin, C. C.
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Lee, C. Y.
This study demonstrated the high CRI and excellent uniformity colloidal quantum dot white-light-emitting diodes with the DBR structure at different correlated color temperature from 2500 K to 4500K.
Highly Efficient GaAs Solar Cells with Dual Layer of Quantum Dots And A Flexible PDMS Film
(2012)
Lin, Chien-chung
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Chen, H. C.
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Chen, K. J.
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Han, H. V.
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Kuo, H. C.
High performance of GaAs solar cell with dual layer quantum dots separated by flexible polydimethylsiloxane film was demonstrated. By this scheme, the efficiency increased by 22 %, compared to the cell without QDs. (C) 2012 Optical Society of America
Improve GaAs Solar Cells Efficiency by Using High-transmittance Textured PDMS Film
(2013)
Han, H. V.
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Chen, H. C.
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Lin, C. C.
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Tsai, Y. L.
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Kuo, H. C.
We demonstrate the GaAs solar cells which utilize the high-transmittance textured polydimethylsiloxane (PDMS) film can outstanding increase the short circuit current density and power conversion efficiency of solar cells. The transmittance of PDMS film is exceeded 90%, which can pass through almost all the light of GaAs Solar cells can be absorbed. We used a special imprint technology to let the PDMS film possess a highly textured surface. Then we measured the characteristics of textured PDMS film and found out that it has a very excellent Haze performance. The effect of flexible textured PDMS film on the suppression of surface reflection in GaAs solar cells is also investigated. The presented technology provides an inexpensive surface anti-reflection process, which can potentially replace typically complex anti-reflection coating (ARC) layer. The GaAs solar cells with textured PDMS layer can effectively enhance the short-circuit current density from 22.91 to 26.54 mA/cm(2) and the power conversion efficiency from 18.28 to 21.43 %, corresponding to a 17 % enhancement compared to the one without textured PDMS. The open-circuit voltage (V-oc) and the fill-factor (FF) of GaAs solar cells exhibit negligible change, because the textured PDMS film was pasted up on the surface of GaAs solar cells and did not interfere with the diode operation. At the same time, we observed through the EQE measurement that the textured PDMS film not only proved wonderful light scattering effect but also generated more electron-hole pairs in all absorption spectrum range. Finally, through this simple PDMS process, we believe this technology shall be a great candidate for next generation of highly efficient and low-cost photovoltaic devices.
Performance enhancement of GaN-based flip-chip ultraviolet light-emitting diodes with a RPD AlN nucleation layer on patterned sapphire substrate
(2014-08-01)
Lin, B. C.
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Chiu, C. H.
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Lee, C. Y.
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Han, H. V.
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Tu, P. M.
In this work, flip-chip ultraviolet light-emitting diodes (FCUV-LEDs) on patterned sapphire substrate (PSS) at 375 nm were grown by an atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD). A specialized reactive plasma deposited (RPD) AlN nucleation layer was utilized on the PSS to enhance the quality of the epitaxial layer. By using high-resolution X-ray diffraction, the full-width at half-maximum of the rocking curve shows that the FCUV-LEDs with RPD AlN nucleation layer had better crystalline quality when compared to conventional GaN nucleation samples. From the transmission electron microscopy (TEM) image, it can be observed that the tip and incline portion of the pattern was smooth using the RPD AlN nucleation layer. The threading dislocation densities (TDDs) are reduced from 7 x 10(7) cm(-2) to 2.5 x 10(7) cm(-2) at the interface between the u-GaN layers for conventional and AlN PSS devices, respectively. As a result, a much higher light output power was achieved. The improvement of light output power at an injection current of 20 mA was enhanced by 30%. Further photoluminescence measurement and numerical simulation confirm such increase of output power can be attributed to the improvement of material quality and light extraction. (C) 2014 Optical Society of America