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Hsu W.-W.,National Taiwan University | Chen J.Y.,National Taiwan University | Cheng T.-H.,National Taiwan University | Lu S.C.,National Taiwan University | And 6 more authors.
Applied Physics Letters | Year: 2012

With Al 2O 3 passivation on the surface of Cu(In,Ga)Se 2, the integrated photoluminescence intensity can achieve two orders of magnitude enhancement due to the reduction of surface recombination velocity. The photoluminescence intensity increases with increasing Al 2O 3 thickness from 5 nm to 50 nm. The capacitance-voltage measurement indicates negative fixed charges in the film. Based on the first principles calculations, the deposition of Al 2O 3 can only reduce about 35 of interface defect density as compared to the unpassivated Cu(In,Ga)Se 2. Therefore, the passivation effect is mainly caused by field effect where the surface carrier concentration is reduced by Coulomb repulsion. © 2012 American Institute of Physics.

Wei K.-C.,Graduate Institute of Electronics Engineering | Huang Y.-L.,National Taiwan University | Chien S.-Y.,Graduate Institute of Electronics Engineering
Proceedings - IEEE International Conference on Multimedia and Expo | Year: 2013

View synthesis, composed of depth-image-based rendering followed by hole-filling, is a crucial technology for 3D TV and free-viewpoint TV. To realize view synthesis in practical systems, the efficiency of view synthesis must be considered to achieve good a trade-off between the image quality and the computational complexity. We propose a efficient view synthesis scheme that, when compared to state-of-the-art backward warping, requires only half of the runtime with comparable quality. Specifically, the proposed scheme uses ray casting and pull-push processing to render in one pass, which can be regarded as applying 3D filters in the depth-image-based rendering. Moreover, the proposed scheme can benefit the hole-filling process to further improve the efficiency of view synthesis. © 2013 IEEE.

Subramani T.,Graduate Institute of Photonics and Optoelectronics | Syu H.-J.,Graduate Institute of Photonics and Optoelectronics | Liu C.-T.,Graduate Institute of Photonics and Optoelectronics | Hsueh C.-C.,Graduate Institute of Photonics and Optoelectronics | And 4 more authors.
ACS Applied Materials and Interfaces | Year: 2016

Nanostructured silicon hybrid solar cells are promising candidates for a new generation photovoltaics because of their light-trapping abilities and solution processes. However, the performance of hybrid organic/Si nanostructure solar cells is hindered because of carrier recombination at surface and poor coverage of organic material poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) on nanostructures. Here we demonstrate low-pressure-assisted coating method of PEDOT:PSS on surface-modified silicon nanotips with broadband light-trapping characteristics to improve interface property and to achieve high-efficiency hybrid solar cells through a solution process. The approach enhances the effective minority-carrier lifetime and the coverage of PEDOT:PSS on the surface of nanostructures. Hybrid solar cells fabricated with surface-modified nanotips exhibit a high fill factor of 70.94%, short-circuit current density of 35.36 mA/cm2, open-circuit voltage of 0.528 V, and power conversion efficiency of 13.36%. The high efficiency and the high fill factor are achieved because of conformal coating of PEDOT:PSS via a low-pressure-assisted coating process, excellent light harvesting without sacrificing the minority-carrier lifetime, and efficient charge separation/collection of photogenerated carriers. © 2015 American Chemical Society.

Chen Y.-J.E.,Graduate Institute of Electronics Engineering | Yang H.-S.,Graduate Institute of Electronics Engineering | Chen J.-H.,National Taiwan University
2014 IEEE International Wireless Symposium, IWS 2014 | Year: 2014

The pulse-modulated polar transmitters have been developed to answer the call for the need of linear and efficient power amplification for wireless applications. The envelope of the modulated RF signal is converted into the pulse train by means of pulse width modulation or delta-sigma modulation. The power amplification of the pulse train can be performed by the highly efficient power amplifiers without the constraint of linearity. The modulated RF signal are restored by low-pass or band-pass filtering of the amplified pulse train. With both high linearity and high efficiency, the pulse-modulated polar transmitter is an excellent candidate for spectrum efficient wireless applications. © 2014 IEEE.

Li W.-T.,National Taiwan University | Tsai J.-H.,National Taiwan Normal University | Yang H.-Y.,National Taiwan University | Chou W.-H.,HTC Corp | And 4 more authors.
IEEE Transactions on Microwave Theory and Techniques | Year: 2012

Two V-band low-noise amplifiers (LNAs) with excellent linearity and noise figure (NF) using 90-nm CMOS technology are demonstrated in this paper, employing parasitic-insensitive linearization topologies, i.e., cascode and common source, for comparative purposes. To improve the linearity without deteriorating the NF, the 54-69-GHz cascode LNA is linearized by the body-biased post-distortion, and the 58-65-GHz common-source LNA is linearized by the distributed derivative superposition. Using these parasitic-insensitive linearization methods at millimeter-wave frequency, the cascode LNA can achieve an IIP 3 of 11 dBm and an NF of 3.78 dB at 68.5 GHz with a gain of 13.2 dB and 14.4-mW dc power. The common-source LNA has an IIP 3 of 0 dBm and an NF of 4.1 dB at 64.5 GHz with a gain of 11.3 dB and 10.8-mW dc power. To the best of our knowledge, the proposed cascode LNA has up to 11-dBm IIP 3 performance and the highest figure-of-merit of 156.2, among all reported V-band LNAs. © 1963-2012 IEEE.

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