Seung-Yoon Lee - Academia.edu (original) (raw)

Papers by Seung-Yoon Lee

2009 34th IEEE Photovoltaic Specialists Conference (PVSC), 2009

ABSTRACT Effects of crystallinity of the p window layers in the pin solar cells having hydrogenat... more ABSTRACT Effects of crystallinity of the p window layers in the pin solar cells having hydrogenated microcrystalline silicon (μc-Si:H) films as an absorber layer on solar cell performance are investigated through the evaluation of the photovoltaic characteristics of solar cells prepared by varying the gas ratio of SiH4/H2 during the p layer deposition. By Raman scattering spectroscopy analysis, it is observed that the volume fraction of crystalline/amorphous phases (Xc) of p layers decreases from 31.0% to 5.1% with increasing the SiH4 concentration from 0.2 to 1.0 sccm at fixed H2 of 180 sccm. Depending on the Xc of the p layers, the solar cell performance is affected significantly, where the solar cells with the p window layers of low Xc represent good photovoltaic characteristics, namely high open circuit voltage (Voc) and short circuit current density (Jsc). Some experimental results and discussion about relationship between crystalline structure of p layers and performance of μc-Si:H solar cells will be presented briefly in this paper.

Current Applied Physics, 2015

The Al-doped ZnO (ZnO:Al) front transparent conducting oxide (TCO) for high efficiency Si thin-fi... more The Al-doped ZnO (ZnO:Al) front transparent conducting oxide (TCO) for high efficiency Si thin-film solar cell has been developed using RF magnetron sputtering deposition and chemical wet etching. Microscopic surface roughness of the as-deposited ZnO:Al film estimated by spectroscopic ellipsometry is closely related to the compactness of the TCO film, and shown to be a straightforward and powerful tool to optimize the deposition conditions for the proper post-etched surface morphology. Wet-etching time is adjusted to form the U-shaped craters on the surface of the ZnO:Al film without sharp etch pits that can cause the crack-like defects in the overgrown microcrystalline Si-absorbing layers, and deteriorate the V oc and FF of the Si thin-film solar cells. That is to say, the nanoroughness control of the as-deposited TCO film with proper chemical etching is the key optimization factor for the efficiency of the solar cell. The a-Si:H/a-SiGe:H/mc-Si:H triple junction Si thin-film solar cells grown on the optimized ZnO:Al front TCO with anti-reflection coatings show higher than 14% conversion efficiency.

MRS Proceedings, 2011

ABSTRACTWe have propsed MgO/AZO bi-layer transparent conducting oxide (TCO) for thin film solar c... more ABSTRACTWe have propsed MgO/AZO bi-layer transparent conducting oxide (TCO) for thin film solar cells. From XRD analysis, it was observed that the full width at half maximum of AZO decreased when it was grown on MgO precursor. The Hall mobility of MgO/AZO bi-layer was 17.5cm2/Vs, whereas that of AZO was 20.8cm2/Vs. These indicated that the crystallinity of AZO decreased by employing MgO precursor. However, the haze (=total diffusive transmittance/total transmittance) characteristics of highly crystalline AZO was significantly improved by MgO precursor. The average haze in the visible region increased from 14.3 to 48.2%, and that in the NIR region increased from 6.3 to 18.9%. The reflectance of microcrystalline silicon solar cell was decreased and external quantum efficiency was significantly improved by applying MgO/AZO bi-layer TCO. The efficiency of microcrystalline silicon solar cell with MgO/AZO bi-layer front TCO was 6.66%, whereas the efficiency of one with AZO single TCO was ...

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2005

Controlling defects on the extreme ultraviolet lithography ͑EUVL͒ mask has become a critical issu... more Controlling defects on the extreme ultraviolet lithography ͑EUVL͒ mask has become a critical issue among many EUVL element technologies. We have conducted experiments to investigate the correctability of two kinds of major defect types, phase and amplitude defects. Phase defects correctability was addressed by using the electron-beam local heating method and amplitude defects correctability were done by using the focused ion-beam ͑FIB͒. Additionally, two kinds of multilayers, Mo/ Si and Mo/ Ru/ Si, were used as substrates to inspect the behavior in a comparative way. As a result, the sink brought by electron-beam ͑e-beam͒ localized heating on a planar multilayer surface was about 8 and 13.6 nm in Mo/ Si and Mo/ Ru/ Si multilayers, respectively, under the e-beam dose of 250 C/cm 2. However, the heating effect was limited to within a few layers from the surface. FIB etching was also conducted on a planar surface of a multilayer. There are two types of FIB correction methods, image mode and spot mode. The etched area was relatively large ͑ϳ3 m ϫ 3 m͒ in image mode. But in the spot mode, the etched area could be confined to a few tens of nanometers in diameter. This FIB method also caused some damage on the multilayer surface.

Thin Solid Films, 2010

ABSTRACT Dual comb-type electrodes were developed as a plasma source in very high frequency (VHF)... more ABSTRACT Dual comb-type electrodes were developed as a plasma source in very high frequency (VHF) plasma enhanced chemical vapor deposition system for uniform deposition of silicon films. Two VHF powers introduced to each electrode produced parallel plasma bands, and their positions could be changed by manipulating the phase difference between the supplied VHF waves. Excitation frequency was 80MHz. The maximum plasma density using this plasma source was 1.5×1010/cm3 and the electron temperature was around 2eV with input power of 2.5kW, which were measured by double tip Langmuir probe. The uniformity of deposition rate under ±13% was achieved on 1m2 area with optimal plasma conditions.

Japanese Journal of Applied Physics, 2003

Extreme ultraviolet (EUV) reflective multilayers that contain a Ru barrier layer at the Moon -Si ... more Extreme ultraviolet (EUV) reflective multilayers that contain a Ru barrier layer at the Moon -Si interface were deposited by multitarget magnetron sputtering. The microstructure, stacking quality, and optical properties of these multilayers were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM), and EUV reflectometry. The multilayers with a Ru barrier showed a more distinct Ru-on-Si interface and suppressed interfacial mixing during deposition. As a result, the peak reflectivity and Full width at half maximum (FWHM) were improved by 1.7% and 50%, respectively, as compared to the conventional Mo/Si multilayer structure.

Current Applied Physics, 2013

The carrier mobility of sputter-deposited Al-doped ZnO transparent-conducting (ZnO:Al) thin films... more The carrier mobility of sputter-deposited Al-doped ZnO transparent-conducting (ZnO:Al) thin films was controlled between 22 and 48 cm 2 /Vs by varying the ZnO:Al seed layer. The statistical distribution of the [001] grain misorientation was characterized from the X-ray diffraction rocking curve in the range from 0.043 (2.5) to 0.179 rad (10.2). The grain-boundary energy barriers (E b) from Seto's model [1] clearly exhibit linear dependence on the grain-boundary misorientation angle (u) according to the equation E b ¼ 78 AE 4 þ 173 AE 32 u meV.

Current Applied Physics, 2012

We investigated bipolar resistance switching (RS) behavior of a top electrode/epitaxial NiO using... more We investigated bipolar resistance switching (RS) behavior of a top electrode/epitaxial NiO using Al and Pt as the top electrodes (TEs) and epitaxial NiO deposited at 500 C (NiO-500) and 700 C (NiO-700). We found that the contact between Al and Pt TEs and NiO-500 was a high resistance insulating contact, while the contact between the two TEs and NiO-700 was a low-resistance metallic contact. We also found that only NiO-500 with the Pt TE exhibited bipolar RS after an electroforming process. This study suggests that during the formation of the Pt/NiO-500 interface, the amount and behavior of oxygen at the interface seem to play the most important role in bipolar RS behavior. In order to improve the device performance, better control of oxygen content and its movement at the interface seems necessary.

Solar Energy Materials and Solar Cells, 2014

The contact resistance of amorphous Si (a-Si:H)/transparent-conducting oxide (TCO) is evaluated a... more The contact resistance of amorphous Si (a-Si:H)/transparent-conducting oxide (TCO) is evaluated and analyzed in terms of the contribution to the series resistance (R s) and fill factor (FF) in the Si heterojunction back-contact (HBC) solar cell. It is shown that p-a-Si:H (emitter) and n-a-Si:H (back surface field: BSF)/TCO contact resistance are of similar values (0.37-38 Ω cm 2) which are much higher than those of doped crystalline Si/metal contacts used in conventional Si solar cells. Of some factors affecting R s loss in the HBC solar cell, BSF/TCO contact is the most significant one when considering the contact area. By interleaving the n-type microcrystalline Si (n-μc-Si) between n-a-Si:H and TCO, 6-inch HBC solar cell with 20.5% efficiency is obtained, which was attributed to the reduced R s and improved FF. It is noteworthy that the variations of R s and FF are well estimated by measuring BSF-contact resistance, and are close to the empirical data: reduction in R s to 1.77 Ω cm 2 and the increase in FF by 6.0% compared to the cell without n-μc-Si interface layer. The results indicate that there is much room for higher efficiency by reducing the emitter-and BSF-contact resistance. Nonetheless, the method developed here can be a powerful tool to analyze the resistance component in HBC cell.