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Hyeongsik Park,Doyoung Kim,Eun-Chel Cho,Shahzada Qamar Hussain,Jeongeun Park,Donggun Lim,Sangho Kim,Subhajit Dutta,Mallem Kumar,Youngkuk Kim,Junsin Yi 한국물리학회 2020 Current Applied Physics Vol.20 No.1
In this study, we investigated the effect of plasma treatment on an indium tin oxide (ITO) film under an ambient Ar atmosphere. The sheet resistance of the plasma-treated ITO film at 250W (37.6 Ω/sq) was higher than that of the as-deposited ITO film (34 Ω/sq). Plasma treatment was found to decrease the ITO grain size to 21.81 nm, in comparison with the as-deposited ITO (25.49 nm), which resulted in a decrease in the Hall mobility. The work function of the Ar-plasma-treated ITO (WFITO=4.17 eV) was lower than that of the as-deposited ITO film (WFITO=5.13 eV). This lower work function was attributed to vacancies that formed in the indium and oxygen vacancies in the bonding structure. Rear-emitter silicon heterojunction (SHJ) solar cells fabricated using the plasma-treated ITO film exhibited an open circuit voltage (VOC) of 734 mV, compared to SHJ cells fabricated using the as-deposited ITO film, which showed a VOC of 704 mV. The increase in VOC could be explained by the decrease in the work function, which is related to the reduction in the barrier height between the ITO and a-Si:H (n) of the rear-emitter SHJ solar cells. Furthermore, the performance of the plasma-treated ITO film was verified, with the front surface field layers, using an AFORS-HET simulation. The current density (JSC) and VOC increased to 39.44 mA/cm2 and 736.8 mV, respectively, while maintaining a WFITO of 3.8 eV. Meanwhile, the efficiency was 22.9% at VOC=721.5 mV and JSC=38.55 mA/cm2 for WFITO=4.4 eV. However, an overall enhancement of 23.75% in the cell efficiency was achieved owing to the low work function value of the ITO film. Ar plasma treatment can be used in transparent conducting oxide applications to improve cell efficiency by controlling the barrier height.
Moisture evaporation prediction model for fresh storage of vegetables in refrigerator
Hyeongsik Kim,Jooshin Kim,Youngmin Park,박상후 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4
This work aims to predict the moisture evaporation in vegetable storage drawers of a household refrigerator with considering the operating conditions of a refrigerator and to propose a prediction model of moisture preservation for a long-term storage of vegetables. An experimental equipment was setup to evaluate the operating conditions, such as temperature and humidity control, cold airflow path, and structural design of a drawer. Moisture evaporation in fresh vegetables was evaluated quantitatively, and a new predictive model of moisture evaporation was developed on the basis of the data. The coefficient of determination was 93.2 % in the prediction model developed when spinach and bok choy were used in the basic experiment, which matched well with the experimental data obtained from a real refrigerator test with difference of approximately 0.4 %. We believe that the proposed approach can be utilized in the initial design stage of a vegetable drawer of a household refrigerator and is expected to be implemented in diverse applications related to fresh storage of vegetables.
Present Status of Thin Film Solar Cells Using Textured Surfaces: A Brief Review
Hyeongsik Park,SHAIKHMOHAMMAD IFTIQUAR,Anh Huy Tuan Le,Shihyun Ahn,강준영,Yongjun Kim,Junsin Yi,Sunbo Kim,신명훈 한국전기전자재료학회 2016 Transactions on Electrical and Electronic Material Vol.17 No.5
This is a brief review on light trapping in Si based thin film solar cells with textured surfaces and transparentconducting oxide front electrodes. The light trapping scheme appears to be essential in improving device efficiencyover 10%. As light absorption in a thin film solar cells is not sufficient, light trapping becomes necessary to beeffectively implemented with a textured surface. Surface texturing helps in the light trapping, and thereby raises shortcircuit current density and its efficiency. Such a scheme can be adapted to single junction as well as tandem solar cell,amorphous or micro-crystalline devices. A tandem cell is expected to have superior performance in comparison to asingle junction cell and random surface textures appears to be preferable to a periodic structures.
Present Status of Thin Film Solar Cells Using Textured Surfaces: A Brief Review
Park, Hyeongsik,Iftiquar, S.M.,Le, Anh Huy Tuan,Ahn, Shihyun,Kang, Junyoung,Kim, Yongjun,Yi, Junsin,Kim, Sunbo,Shin, Myunghun The Korean Institute of Electrical and Electronic 2016 Transactions on Electrical and Electronic Material Vol.17 No.5
This is a brief review on light trapping in Si based thin film solar cells with textured surfaces and transparent conducting oxide front electrodes. The light trapping scheme appears to be essential in improving device efficiency over 10%. As light absorption in a thin film solar cells is not sufficient, light trapping becomes necessary to be effectively implemented with a textured surface. Surface texturing helps in the light trapping, and thereby raises short circuit current density and its efficiency. Such a scheme can be adapted to single junction as well as tandem solar cell, amorphous or micro-crystalline devices. A tandem cell is expected to have superior performance in comparison to a single junction cell and random surface textures appears to be preferable to a periodic structures.
Park, Hyeongsik,Lee, Youn-Jung,Park, Jinjoo,Kim, Youngkuk,Yi, Junsin,Lee, Youngseok,Kim, Sangho,Park, Chang-Kyun,Lim, Kyung-Jin The Korean Institute of Electrical and Electronic 2018 Transactions on Electrical and Electronic Material Vol.19 No.3
In this paper, we report a technical approach regarding an amorphous silicon (a-Si)/crystalline silicon (c-Si) heterojunction solar cell to solve the previous issues, and we investigate the applications of front and back transparent conductive oxides (TCOs) on this high-efficiency solar cell. The presentation of front and rear-emitter structure solar cells is included, and we investigate the TCO-material candidates for the Si heterojunction (SHJ) solar cell according to the electrical and optical properties. A high-quality TCO film is very important because it is linked to the efficiency of the c-Si-based silicon solar cell. The intention here is the applying of a high-efficiency SHJ solar cell by fabricating the high-quality TCO materials of the investigation of this study.
Park, Hyeongsik,Shin, Myunghun,Kim, Hyeongseok,Kim, Sunbo,Le, Anh Huy Tuan,Kang, Junyoung,Kim, Yongjun,Pham, Duy Phong,Jung, Junhee,Yi, Junsin Elsevier 2017 Optical materials Vol.66 No.-
<P><B>Abstract</B></P> <P>A comparative study of 3-dimensional textured glass morphologies with variable haze value and chemical texturing of the glass substrates was conducted to enhance light trapping in silicon (Si) thin film solar cells (TFSCs). The light trapping characteristics of periodic honeycomb structures show enhanced transmittance and haze ratio in numerical and experimental approaches. The periodic honeycomb structure of notched textures is better than a random or periodic carved structure. It has high transmittance of ∼95%, and haze ratio of ∼52.8%, and the haze property of the angular distribution function of transmittance shows wide scattering angles in the long wavelength region because of the wide spacing and aspect ratio of the texture. The numerical and experimental approaches of the 3-D texture structures in this work will be useful in developing high-performance Si TFSCs with light trapping.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 3-D Light trapping structures are investigated for Si thin film solar cells. </LI> <LI> A glass texturing method is developed using chemical solutions of diluted HF. </LI> <LI> FDTD simulation shows a notched periodic honeycomb texture will be effective one. </LI> <LI> Periodic texturing shows better light scattering performance than random structures. </LI> <LI> Fabricated periodic honeycomb structure shows high transmittance and haze values. </LI> </UL> </P>
Park, Hyeongsik,Shin, Myunghun,Kim, Hyeongseok,Kim, Sunbo,Le, Anh Huy Tuan,Kim, Youngkuk,Ahn, Shihyun,Jeong, Jae-Seong,Yi, Junsin American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.11
<P>A glass texturing process was developed to enhance the light scattering in the wideband wavelength range for thin-film hydrogenated amorphous silicon solar cells. Periodic honeycomb structures were patterned on glass substrates by a simple photolithography and chemical wet-etching process using HF (10%) solutions. We investigated the optical properties of the textured glasses for various etching times (i.e., the statuses of the etching steps), which were characterized using optical measurements and finite-difference time-domain simulations. We found the reproducible texturing conditions for obtaining high transmittance and haze values, and the angular distribution measurements showed that the scattered light is diffracted and trapped within the solar cell. The textured glass substrates showed a maximum transmittance of 95.5% and a haze ratio of about 61% in the wideband wavelength range, and the finite-difference time-domain simulation expected a very high short-circuit current density of 21.9 mA/cm(2) for a single-junction thin-film hydrogenated amorphous silicon solar cell employing the honeycomb textured glass substrates, which will be useful for developing high-performance thin-film hydrogenated amorphous silicon solar cells.</P>