• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.1-20
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• 2020

Development of efficient methods for clean energy production became a critical issue to improve the quality of human lives. Solar cells is considered as one of the alternative solutions to resolve the issue. Although Si-based solar cells are only popularly utilized for practical applications, high manufacturing cost is considered as a serious drawback for further versatile applications. Thus, different types of are being investigated aiming to replace the Si-based solar cells. Recently, perovskite solar cells (PSC) are considered as a potential replacement for Si-based solar cells due to their low production cost, high power conversion efficiency, light weight and possibility of flexible device fabrication. Thus, we have reviewed the challenges of PSC faced with practical application, particularly on stability.

• Journal of the Korean Solar Energy Society
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• v.33 no.2
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• pp.11-17
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• 2013

Silicon nitride($SiN_x:H$) deposited by radio frequency plasma enhanced chemical vapor deposition(RF-PECVD) is commonly used for anti-reflection coating and passivation in crystalline silicon solar cell fabrication. In this paper, characteristics of the deposited silicon nitride was studied with change of working pressure, deposition temperature, gas ratio of $NH_3$ and $SiH_4$, and RF power during deposition. The deposition rate, refractive index and effective lifetime were analyzed. The (100) p-type silicon wafers with one-side polished, $660-690{\mu}m$, and resistivity $1-10{\Omega}{\cdot}cm$ were used. As a result, when the working pressure increased, the deposition rate of SiNx was increased while the effective life time for the $SiN_x$-deposited wafer was decreased. The result regarding deposition temperature, gas ratio and RF power changes would be explained in detail below. In this paper, the optimized condition in silicon nitride deposition for silicon solar cell was obtained as 1.0 Torr for the working pressure, $400^{\circ}C$ for deposition temperature, 500 W for RF power and 0.88 for $NH_3/SiH_4$ gas ratio. The silicon nitride layer deposited in this condition showed the effective life time of > $1400{\mu}s$ and the surface recombination rate of 25 cm/s. The crystalline silicon solar cell fabricated with this SiNx coating showed 18.1% conversion efficiency.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.51-55
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• 2011

In this paper, the optimized doping condition of crystalline silicon solar cells with 156 ${\times}$ 156 mm2 area was studied. To optimize the drive-in condition in the doping process, the other conditions except drive-in temperature and time were fixed. After etching 7 ${\mu}m$ of the surface to form the pyramidal structure, the silicon nitride deposited by the PECVD had 75~80 nm thickness and 2 to 2.1 for a refractive index. The silver and aluminium electrodes for front and back sheet, respectively, were formed by screen-printing method, followed by firing in $400-425-450-550-850^{\circ}C$ five-zone temperature conditions to make the ohmic contact. Drive-in temperature was changed in range of $828^{\circ}C$ to $860^{\circ}C$ and time was from 3 min to 40 min. The sheet resistance of wafer was fixed to avoid its effect on solar cell. The solar cell fabricated with various conditions showed the similar conversion efficiency of 17.4%. This experimental result showed the drive-in temperatures and times little influence on solar cell characteristics.

• Journal of the Korean Solar Energy Society
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• v.31 no.1
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• pp.37-43
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• 2011

In this paper, the optimized doping condition of crystalline silicon solar cells with $156{\times}156\;mm^2$ area was studied. To optimize the drive-in temperature in the doping process, the other conditions except variable drive-in temperature were fixed. These conditions were obtained in previous studies. After etching$7\;{\mu}m$ of the surface to form the pyramidal structure, the silicon nitride deposited by the PECVD had 75~80nm thickness and 2 to 2.1 for a refractive index. The silver and aluminium electrodes for front and back sheet, respectively, were formed by screen-printing method, followed by firing in 400-425-450-550-$850^{\circ}C$ five-zone temperature conditions to make the ohmic contact. Drive-in temperature was changed in range of $830^{\circ}C$ to $890^{\circ}C$to obtain the sheet resistance $30{\sim}70\;{\Omega}/{\box}$ with $10\;\Omega}/{\box}$ intervals. Solar cell made in $890^{\circ}C$ as the drive-in temperature revealed 17.1% conversion efficiency which is best in this study. This solar cells showed $34.4\;mA/cm^2$ of the current density, 627 mV of the open circuit voltage and 79.3% of the fill factor.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.347-348
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• 2013

To obtain high conversion efficiency in InGaN-based solar cells, it is critical to grow high indium (In) composed InGaN layer for increasing sun light absorption wavelength rage. At present, most InGaN-based solar cells adopt InGaN/GaN multi-quantum-well (MQW) structure for high crystalline quality of InGaN with high In composition. In this study, we fabricated and compared the performances of two types of InGaN/GaN MQW solar cells which have the 15% (SC 15) and 25% (SC 25) of In composition at quantum well layer. Although both devices showed similar dark current density and leakage current, SC 15 showed better performance under AM 1.5G illumination as shown in Fig. 1. It is interesting to note that SC 25 showed severe current density decrease as increasing voltages. As a result, it lowered short circuit current density and fill factor of the device. However, SC 15 showed steady current density and over 75 % of fill factor. To investigate these differencesmore clearly, we analyzed their photoluminescence (PL) spectra under various applied voltages as shown in Fig. 2. At the same time, photocurrent, which was generated by PL excitation, was also measured as shown in Fig. 3. Further, we investigated the relationship between piezoelectric field and performance of InGaN based solar cell varying indium composition.

• Korean Journal of Materials Research
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• v.27 no.2
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• pp.94-99
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• 2017

Dinickel-silicide $(Ni_2Si)/glass$ was employed as a counter electrode for a dye-sensitized solar cell (DSSC) device. $Ni_2Si$ was formed by rapid thermal annealing (RTA) at $700^{\circ}C$ for 15 seconds of a 50 nm-Ni/50 nm-Si/glass structure. For comparison, $Ni_2Si$ on quartz was also prepared through conventional electric furnace annealing (CEA) at $800^{\circ}C$ for 30 minutes. XRD, XPS, and EDS line scanning of TEM were used to confirm the formation of $Ni_2Si$. TEM and CV were employed to confirm the microstructure and catalytic activity. Photovoltaic properties were examined using a solar simulator and potentiostat. XRD, XPS, and EDS line scanning results showed that both CEA and RTA successfully led to tne formation of nano $thick-Ni_2Si$ phase. The catalytic activity of $CEA-Ni_2Si$ and $RTA-Ni_2Si$ with respect to Pt were 68 % and 56 %. Energy conversion efficiencies (ECEs) of DSSCs with $CEA-Ni_2Si$ and $RTA-Ni_2Si$catalysts were 3.66 % and 3.16 %, respectively. Our results imply that nano-thick $Ni_2Si$ may be used to replace Pt as a reduction catalytic layer for a DSSCs. Moreover, we show that nano-thick $Ni_2Si$ can be made available on a low-cost glass substrate via the RTA process.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.175-180
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• 2011

In this study, the $TiO_{2}/V_{2}O_{5}$ hybrid semiconductors were prepared by mixing $TiO_{2}$ and $V_{2}O_{5}$, and a subsequent smash process to reduce the recombination of electron and improve the efficiency of solar cells. Dye-sensitized solar cells were constructed using the resultant hybrid semiconductor, and their electrochemical properties were also investigated. The photocurrent-voltage curve obtained with the cells indicated a significant increase in the efficiency from 2.9 to 5.7% by the factor of 2 compared to the result obtained only with $TiO_{2}$. It is believed that the introduction of $V_{2}O_{5}$ effectively transport electrons in the $TiO_{2}$ conduction band to FTO glass and suppress recombination with the dye and/or the electrolyte, thus yielding an efficient performance of the dye sensitized solar cell. The impedance values also indicated a decrease of resistance in the interface of $TiO_{2}$/dye/electrolyte supporting the constructive contributions of the smashed $TiO_{2}/V_{2}O_{5}$ hybrid semiconductors for the efficiency.

• Current Photovoltaic Research
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• v.4 no.3
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• pp.108-113
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• 2016

III-V compound semiconductor based thin film solar cells promise relatively higher power conversion efficiencies and better device reliability. In general, the thin film III-V solar cells are fabricated by an epitaxial lift-off process, which requires an $Al_xGa_{1-x}As$ ($x{\geq}0.8$) sacrificial layer and an inverted solar cell structure. However, the device performance of the inversely grown solar cell could be degraded due to the different internal diffusion conditions. In this study, InGaP/GaAs double-junction solar cells are inversely grown by MOCVD on GaAs (100) substrates. The thickness of the GaAs base layer is reduced to minimize the thermal budget during the growth. A wide band gap p-AlGaAs/n-InGaP tunnel junction structure is employed to connect the two subcells with minimal electrical loss. The solar cell structures are transferred on to thin metal films formed by Au electroplating. An AlAs layer with a thickness of 20 nm is used as a sacrificial layer, which is removed by a HF:Acetone (1:1) solution during the epitaxial lift-off process. As a result, the flexible InGaP/GaAs solar cell was fabricated successfully with an efficiency of 27.79% under AM1.5G illumination. The efficiency was kept at almost the same value after bending tests of 1,000 cycles with a radius of curvature of 10 mm.

• Solar Energy
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• v.10 no.3
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• pp.46-52
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• 1990

Novel a-Si solar cells with delta-doped(${\delta}x$-doped) P-layer have been fabricated to enhance the hole concentration of the P-layers. The ${\delta}-$doped P-layer consists of very thin B sheets of 0.1-0.5 atomic layers and undoped a-SiC multi-layers. B-layers were prepared by photo-CVD and pyrolysis technique. The structural, optical and electrical characteristics of the delta-doped P-layer films were evaluated by means of FTIR, AES and SIMS. As the results of this study, it was found that the ${\delta}$-doped P-layer showed much superior optical and electrical characteristics than those of conventional uniformly B-doped a-Si layers. 12.5% energy conversion efficiency was achieved for the Cell with ${\delta}$-doped P-layer.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.49.2-49.2
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• 2010

Polycrystalline CdTe thin films for solar cell continues to be a promising material for the development of cost effective and reliable photovoltaic processes. The two key advantages of this material are its high optical absorption coefficient and its near ideal band gap for photovoltaic conversion efficiency of 1.4-1.5 eV. In this study we made the CdTe thin films for solar cell application which was deposited on the glass substrates using a modified chemical spray method at low temperature. This process does not require the sophisticated and expensive vacuum systems. The prepared CdTe films were characterized with the aid of scanning electron microscope (SEM), UV-visible spectrophotometer, and X-ray diffraction spectrometer (XRD). Following are results of a study on the "Human Resource Development Center for Economic Region Leading Industry" Project, supported by the Ministry of Education, Science & Tehnology(MEST) and the National Research Foundation of Korea(NRF).