Minkyoung Choi

Properties of a Dye Sensitized Solar Cell using Electrodes with Au Nano Powder Blocking Layers

Jeongho Song, Yunyoung Noh, Minkyoung Choi, Kwangbae Kim, and Ohsung Song* Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Republic of Korea Abstract: We prepared working electrodes with blocking layers containing 0.0∼0.5 wt% Au nano powder to improve the energy conversion efficiencies (ECEs) of a dye sensitized solar cell (DSSC). TEM, FE-SEM, and AFM were used to characterize microstructure. XRD and micro-Raman were used to determine the phase and localized surface plasmon resonance (LSPR) effect of the blocking layer with Au nano powder. A solar simulator and a potentiostat were used to confirm the photovoltaic properties of the DSSC with the Au nano powder. From the results of the microstructure analysis, we confirmed that the Au nano powder had particle sizes of less than 70 nm, dispersed uniformly on the blocking layer. Based on the phase and composition analysis, we identified the presence of Au, and the Raman intensity increased as the amount of Au was increased. The photovoltaic results showed that the ECE reached 5.52% with the Au addition, compared to an ECE of 5.00% without the Au addition. This enhancement was due to the increased LSPR of the blocking layer with the Au addition. Our results suggest that we might improve the efficiency of a DSSC by the proper addition of Au nano powder on the blocking layer. †(Received November 24, 2015; Accepted February 22, 2016)

Properties of Dye Sensitized Solar Cells with Porous TiO2 Layers Using Polymethyl-Methacrylate Nano Beads

We prepared polymethyl methacrylate (PMMA) beads with a particle size of 80 nm to improve the energy conversion efficiency (ECE) by increasing the effective surface area and the dye absorption ability of the working electrodes (WEs) in a dye sensitized solar cell (DSSC). We prepared the TiO2 layer with PMMA beads of 0.0~1.0 wt%; then, finally, a DSSC with 0.45 cm2 active area was obtained. Optical microscopy, transmission electron microscopy, field emission scanning electron microscopy, and atomic force microscopy were used to characterize the microstructure of the TiO2 layer with PMMA. UV-VIS-NIR was used to determine the optical absorbance of the WEs with PMMA. A solar simulator and a potentiostat were used to determine the photovoltaic properties of the PMMA-added DSSC. Analysis of the microstructure showed that pores of 200 nm were formed by the decomposition of PMMA. Also, root mean square values linearly increased as more PMMA was added. The absorbance in the visible light regime was found to increase as the degree of PMMA dispersion increased. The ECE increased from 4.91% to 5.35% when the amount of PMMA beads added was increased from 0.0 to 0.4 wt%. However, the ECE decreased when more than 0.6 wt% of PMMA was added. Thus, adding a proper amount of PMMA to the TiO2 layer was determined to be an effective method for improving the ECE of a DSSC.

Properties of the Master Alloys for White Gold Products with Silicon Contents

Abstract We prepared 8 samples of non-silver and silver-added master alloys containing silicon to confirm the existence ofnickel-silicides. We then prepared products made of 14K and 18K white gold by using the prepared master alloys containing0.25, 0.35, and 0.50 wt% silicon to check for nickel release. We then employed the EN 1811 testing standard to investigatethe nickel release of the white gold products, and we also confirmed the color of the white gold products with an UV-VIS-NIR-color meter. We observed NiSi x residue in all master alloys containing more than 0.50 wt% Si with EDS-nitric acid etching.For the white gold products, we could not confirm the existence of NiSi x through XRD after aqua-regia etching. In the EN1811 test, only the white gold products with 0.25 wt% silicon master alloys successfully passed the nickel release regulations.Moreover, we confirmed that our white gold products showed excellent Lab indices as compared to those of commercial whitegold ones, and the silver-added master alloys offered a larger L index. Our results indicate that employing 0.25 wt% siliconmaster alloys might be suitable for white gold products without nickel-silicide defects and nickel release problems. Key wordsmaster alloy, white gold, silicon content, nickel release, energy dispersive spectroscopy.