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Ahn, Shihyun,Iftiquar, S M,Cho, Jaehyun,Le, Anh Huy Tuan,Park, Cheolmin,Park, Jinjoo,Lee, Hyunhwa,Hong, Keunkee,Kim, Jung Soo,Bong, Sungjae,Yi, Junsin IOP 2019 Journal of Physics. D, Applied Physics Vol.52 No.3
<P>The efficient capture and absorption of light are important aspects in improving the photovoltaic conversion efficiency of a solar cell. In a two-terminal tandem device, the output current density is limited by the lowest current-generating component sub-cell. We attempted by experiment to improve the current density of both sub-cells, using an inverted pyramid-type textured glass substrate. One of the two surfaces of the glass substrates was textured by semi-anisotropic reactive ion etching (RIE) with a 100 sccm flow rate of SF<SUB>6</SUB> gas, and with 7 <I>µ</I>m × 7 <I>µ</I>m square-shaped etch masks, and obtained an optimum texture of base dimension ~7 <I>µ</I>m, height ~8.5 <I>µ</I>m, tip diameter ~75 nm and tip to tip separation between neighboring pyramids were about 9 <I>µ</I>m. Tandem solar cells that were fabricated on these textured surfaces receive light from the base of these micro-pyramids, thereby enhancing light absorption in the active layers of the device. The shape of the texture and orientation of layers of the tandem solar cell ensured a longer optical path inside the solar cell, leading to higher optical absorption and an improvement in device performance. We observed an increase in the short circuit current density from 11.52 to 14.30 mA cm<SUP>−2</SUP>, and in the device efficiency from 11.97% to 14.22%.</P>
안시현(ShiHyun Ahn),안정훈(JeongHun Ahn) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.4
Most of countries are awaking to the need for cutting fuel consumption and greenhouse gases since 2000. There is a growing need to introduce new safe vehicles for the aged and a physically challenged person. A electric scooter and wheelchair is eco-friendly vehicle making electric battery a alternative to oil and has good features as a mobility assisting vehicle. This paper presents a new method to control Motor Speed with APS and CAN signals a electric scooter and wheelchair. A Motor Speed Control Module designed for new method is composed of MCU(dspic30f6015) and APS signal interface and CAN Transceiver and LCD Controller and switch. These are performed signal conversion from APS signal to CAN signal and motor speed control test with Accelerator Pedal Module and CANoe and MCLV Board.
High Breakdown Voltage (−201) <tex> $\beta $</tex> -Ga2O3 Schottky Rectifiers
Yang, Jiancheng,Ahn, Shihyun,Ren, F.,Pearton, S. J.,Jang, Soohwan,Kuramata, A. IEEE 2017 IEEE electron device letters Vol.38 No.7
<P>beta-Ga2O3 Schottky barrier diodes were fabricated in a vertical geometry structure consisting of Ni/Au rectifying contacts without edge termination on Si-doped epitaxial layers (10 mu m, n similar to 4x10(15) cm(-3)) on Sn-doped bulk Ga2O3 substrates with full-area Ti/Au back Ohmic contacts. The reverse breakdown voltage, V-BR, was a function of rectifying contact area, ranging from 1600 V at 3.1x10(-6) cm(2) (20-mu mdiameter) to similar to 250V at 2.2x10(-3) cm(-2) (0.53-mm diameter). The current density near breakdown was not strongly dependent on contact circumference but did scale with contact area, indicating that the bulk current contributionwas dominant. The lowest ON-state resistance, R-on, was 1.6 m Omega.cm(2) for the largest diode and 25 m Omega.cm(2) for the 1600-V rectifier, leading to a Baliga figure-of-merit (V-BR(2)/R-on) for the latter of approximately 102.4 MW.cm(-2). The ON-OFF ratio was measured at a forward voltage of 1.3 V and ranged from 3x10(7) to 2.5x10(6) for reverse biases from -5 to -40 V and showed only a small dependence on temperature in the range from 25 degrees C to 100 degrees C.</P>
Cui, Jian,Ahn, Shihyun,Balaji, Nagarajan,Park, Cheolmin,Yi, Junsin Korea Photovoltaic Society 2016 Current Photovoltaic Research Vol.4 No.2
n-type PERT (passivated emitter, rear totally diffused) bifacial solar cells with boron and phosphorus diffusion as p+ emitter and n+ BSF (back surface field) have attracted significant research interest recently. In this work, the influences of wafer thickness, bulk lifetime, emitter, BSF on the photovoltaic characteristics of solar cells are discussed. The performance of the solar cell is determined by using one-dimensional solar cell simulation software PC1D. The simulation results show that the key role of the BSF is to decrease the surface doping concentration reducing the recombination and thus, increasing the cell efficiency. A lightly phosphorus doped BSF (LD BSF) was experimentally optimized to get low surface dopant concentration for n type bifacial solar cells. Pre-oxidation combined with a multi-plateau drive-in, using limited source diffusion was carried out before pre-deposition. It could reduce the surface dopant concentration with minimal impact on the sheet resistance.
Jian Cui,Shihyun Ahn,Nagarajan Balaji,Cheolmin Park,Junsin Yi 한국태양광발전학회 2016 Current Photovoltaic Research Vol.4 No.2
n-type PERT (passivated emitter, rear totally diffused) bifacial solar cells with boron and phosphorus diffusion as p+ emitter and n+ BSF (back surface field) have attracted significant research interest recently. In this work, the influences of wafer thickness, bulk lifetime, emitter, BSF on the photovoltaic characteristics of solar cells are discussed. The performance of the solar cell is determined by using one-dimensional solar cell simulation software PC1D. The simulation results show that the key role of the BSF is to decrease the surface doping concentration reducing the recombination and thus, increasing the cell efficiency. A lightly phosphorus doped BSF (LD BSF) was experimentally optimized to get low surface dopant concentration for n type bifacial solar cells. Pre-oxidation combined with a multi-plateau drive-in, using limited source diffusion was carried out before pre-deposition. It could reduce the surface dopant concentration with minimal impact on the sheet resistance.
Bong, Sungjae,Ahn, Shihyun,Anh, Le Huy Tuan,Kim, Sunbo,Park, Hyeongsik,Shin, Chonghoon,Park, Jinjoo,Lee, Younjung,Yi, Junsin American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.5
<P>For thin film silicon-based solar cells, effective light trapping at a broad range of wavelengths (400-1100 nm) is necessary. Normally, etching is only carried out with TCOs, such as SnO2:F and impurity doped ZnO, to form nano-sized craters in the surface morphology to confer a light trapping effect. However, in this study, prior to ZnO: Al etching, periodic structures on the glass substrates were made by photolithography and wet etching to increase the light scattering and internal reflection. The use of periodic structures on the glass substrate resulted in higher haze ratios in the range from 550 nm to 1100 nm, which is the optical absorption wavelength region for thin film silicon solar cells, than obtained by simple ZnO: Al etching. The periodically textured glass with micro-sized structures compensates for the low haze ratio at the middle and long wavelengths of wet etched ZnO: Al. ZnO: Al was deposited on the periodically textured glass, after which the ZnO: Al surface was also etched randomly using a mixed acid solution to form nano-sized craters. The thin film silicon solar cells with 350-nm-thick amorphous silicon absorber layer deposited on the periodic structured glass and etched ZnO: Al generated up to 10.68% more photocurrent, with 11.2% increase of the conversion efficiency compared to the cell deposited on flat glass and etched ZnO: Al.</P>