Browsing by Author "Lin, Yu-Chen"

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Back-Contacted Thin-Film GaAs Solar Cells
(2016-01-01)
Hong, Chung-Yu
;
Lin, Yu-Chen
;
Ho, Kuan-Ying
;
Tsai, Jia-Ling
;
Chien, Zhan-Tien
In this work, we present a thin-film GaAs solar cell employing via contacts for forming a back-contacted solar cell to eliminate light blocking effects and enhance photon recycling at the same time. The fabrication procedure and the characterization of the fabricated devices are discussed in this paper. From our measurement, a conversion efficiency of 6.5%, open circuit voltage of 0.95 V, and a current density of 8.6mA/cm(2) under one-sun illumination were obtained in a 5x5 mm cell.
Control system for an electrostatically-driven microelectromechanical device
(2003-10-09)
Chiou, Jin-Chern
;
Lin, Yu-Chen
The present invention relates to a control system for an electrostatically-driven microelectromechanical device, which uses multiple electrodes to control the microelectromechanical device, i.e. the lower driven electrode of a capacitor with known two parallel driven electrodes Is cut Into a number of small electrodes. By selecting an electrode pattern for a desired electrostatic force, it is capable of altering the non-linearity of the device based on various applications and achieving a characteristic such as a linear driven, digital driven, or ultimately optimal driven manners, which is able to reach high operation accuracy for the existing circuit that only possesses a limited accuracy.
High-brightness and high-speed vertical cavity surface-emitting laser arrays
(2020-04-20)
Khan, Zuhaib
;
Shih, Jie-Chen
;
Chao, Rui-Lin
;
Tsai, Tzong-Liang
;
Wang, Hsin-Chuan
High-power vertical-cavity surface-emitting laser (VCSEL) arrays, which can serve as the light source in modem lidar and three-dimensional optical sensing systems, have recently attracted a lot of attention. In these types of systems, the time-of-flight (ToF) technique, based on the round-trip time of short optical pulses is usually adopted. Further enhancement of the ranging distance and depth resolution in these ToF driven systems by the incorporation of a VCSEL array with a high available power, high brightness (narrow divergence angle), and fast response time is highly deskable. However, a large number of light emission apertures (several hundreds) in the VCSEL array is usually necessary to raise the output power level to several watts. This leads to a large parasitic capacitance and the RC-limited bandwidth may become the dominant limiting factor of the speed of the high-power VCSEL array. In this work, Zn-diffusion and oxide-relief apertures are used to manipulate the optical modes and reduce the parasitic capacitance, respectively, in a unit device for a 940 nm VCSEL array. The demonstrated VCSEL array has a quasi-single-mode output, high available power (4 W; 1% duty cycle), narrow divergence angle (similar to 14 degrees at 1/e(2)) under maximum output power, and a fast rise time (<100 ps). These results open up new possibilities for further enhancing the performance of ToF sensing systems at the 940 nm wavelength. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Photovoltaic Characteristics of GaAs Solar Cells with Selective Filters
(2015)
Hong, Chung-Yu
;
Hung, Mu-Min
;
Yang, Tung-Ting
;
Wang, Yi-Chin
;
Lin, Yu-Chen
Enhancing the photon recycling process in a solar cell can boost the open-circuit voltage (V-oc). In this work, we employ a selective filter realized by alternative TiO2 and SiO2 dielectric layers with different cutoff wavelengths as the front surface structures, and a distributed Bragg reflector (DBR) grown by epitaxy on the rear side of GaAs solar cells to form an optical cavity. The idea is to suppress the radiative recombination emission loss at the material bandgap toward the front and rear side by increasing photon-recycling via a cavity design with minimal auxiliary impact on light current. From our experiment, when cut-off wavelength was designed at 840nm, the V-oc of the cell increase by 1.1mV compared with the device without the selective filter. Moreover, we successfully developed an optical model that combines a rigorous couple wave analysis (RCWA) and photon recycling calculation NREL developed recently to quantify the V-oc enhancement from different optical design on GaAs solar cells. Based on theoretical optimizations of the experimental data, if we can optimize the back DBR reflector or using metal as the back mirror, we can obtain a large V-oc enhancement by 36.4mV using the selective filter with a cut-off wavelength of 840 nm. However, although we can use selective filter as top structure to improve the V-oc, the power conversion efficiency is still limited due to the implementation of selective filters has affected light absorption at the desired spectral range. Nevertheless, this concept of light management may be further improved by using angular filters in order to prevent the loss of light current while improving the V-oc and power conversion efficiency at the same time.
Photovoltaic Characteristics of Multiple Quantum Well Solar Cells with Distributed Bragg Reflector and Selective Filters
(2016-01-01)
Hong, Chung-Yu
;
Wang, Yi-Chin
;
Hung, Mu-Min
;
Su, Yu-Chih
;
Tsai, Jia-Ling
We investigate the photon recycling characteristics of single junction solar cells incorporating 50-pairs multiple quantum wells (MQW) to exploit the high radiative recombination rate in one-dimensional carrier-confinement structures. In particular, we systematically compare solar cells with monolithically grown distributed Bragg reflectors (DBRs), as well as selective filters (SFs) with cutoff wavelengths of 880, 910, and 930 nm under standard and concentrated illumination conditions. Optical confinement in the vertical direction is verified based on the reflective spectra and electroluminescence properties. Consequently, the photo-recycling effect manifests under concentrated conditions, where the maximal open circuit voltage difference, by 12mV under 200x illumination, is achieved for MQW solar cells incorporating both the DBR and the 910-nm-cutoff SF, compared to those without the DBR or SFs. It is also revealed that the fill factor (FF) is also affected by the photon recycling effect, where incorporating SF results in the FF enhancement compared to the counterpart without the SF and the enhancement is higher for those with DBRs than without the DBRs.