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장보윤,김동우,( Suresh Thogiti ),김재홍 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
The effect of temperature variations on the performance of dye-sensitized solar cells (DSSC), based on quasi-solid electrolyte, has been studied under 1 sun irradiance. The cell performance was characterized with J-V curves obtained at different cell operating temperatures and electrochemical impedance spectroscopy measurements before and after the temperature treatments. The measured temperature range was from ca. 25°C to 75°C at an interval of ca. 10°C. The results show the higher temperature, the higher photo-current density of DSSCs. At lower temperatures, the short-circuit current (JSC) is limited by the conductivity of electrolyte, while at higher temperatures, the JSC increases due to more pronounced charge transport.
TiO2 photoelectrode structure with gradations in W concentration for DSSC application
김우철,이용희,( Suresh Thogiti ),이도경,김재홍 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
The transportation of photo-generated electron in dye sensitized solar cells (DSSCs) is one of the most important criteria to enhance their overall power conversion efficiency. The photo-generated electron is injected from the lowest unoccupied molecular orbital of photosensitizer into the conduction band level of TiO2, and then transferred to the conductive transparent electrode. In this work, W-doped TiO2 is introduced as blocking layer with various amount of tungsten dopant. W-doped TiO2 blocking layers are deposited on transparent electrode by spin coating. W-doping leads to increase the short circuit current density due to the enhancement of charge transport rate. However, it causes the decrease in the open circuit voltage because the probability of charge recombination tends to increase with the increase in the amount of W dopant.
Ho, Phuong,Thogiti, Suresh,Bao, Le Quoc,Cheruku, Rajesh,Ahn, Kwang-Soon,Hong Kim, Jae Elsevier 2018 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.161 No.-
<P><B>Abstract</B></P> <P>The efficiency of tandem pn-dye-sensitized solar cells (pn-DSCs) has been limited by the poor performance of the available p-DSCs. A facile approach of introducing a compact NiO blocking layer into an active NiO photocathode network of p-DSCs and pn-DSCs is presented to enrich the power conversion efficiency (PCE) using a Co<SUP>2+/3+</SUP> redox mediator. Two photoelectrodes sensitized with different dyes (SQ for n-DSC and P1 for p-DSC) have a complementary nature in absorbing solar irradiation at different wavelengths. The constructed pn-DSC demonstrates an enhanced photovoltage compared to n-DSC, resulting in an overall PCE of 1.486%. This PCE is further improved to 1.913% by the addition of an optimized NiO blocking layer to the p-DSC; this was prepared <I>via</I> spin-coating with a nickel acetate precursor solution. All photovoltaic parameters were significantly increased with the introduction of a blocking layer compared to a bare cell.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NiO blocking layer was fabricated for Co-based pn-DSCs via spin-coating method. </LI> <LI> The charge recombination was suppressed with a compact NiO blocking layer. </LI> <LI> The charge transfer and lifetime was improved for pn-DSCs with NiO blocking layer. </LI> <LI> Highest PCE of 1.913% achieved by the addition of an optimized NiO blocking layer. </LI> <LI> We have achieved one of the best PCE for pn-DSCs until today. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>A facile approach of introducing a compact NiO blocking layer into an active NiO photocathode network of pn-DSCs is presented to enrich the power conversion efficiency (PCE) using a Co<SUP>2+/3+</SUP> redox mediator. The constructed pn-DSC demonstrates an enhanced photovoltage compared to n-DSC, resulting in an overall PCE of 1.486%. This PCE is further improved to 1.913% by the addition of an optimized NiO blocking layer. All photovoltaic parameters were significantly increased with the introduction of a blocking layer compared to a bare cell.</P> <P>[DISPLAY OMISSION]</P>
김동우,전지훈,( Suresh Thogiti ),( Ganesh Koyyada ),이도경,김재홍 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
The power conversion efficiency of dye-sensitized solar cells has been limited because electron transport is not fully achieved, and the injected electrons always recombine with the acceptor species before the electrode can collect them. The concept of introducing metal-doped TiO<sub>2</sub> blocking layer into the mesoporous TiO<sub>2</sub> network of dye-sensitized solar cells is proposed to enhance the power conversion efficiency. DSSCs based on Mo-TiO<sub>2</sub> blocking layer show an advantage in increasing he charge transport. The charge transfer resistance in DSSC is significantly suppressed by the Mo-doping. As a result of the downward shifted conduction band and increased charge transport, the photocurrent density of the device is improved remarkably with an almost unchanged photovoltage. The highest power conversion efficiency (η = 8.03%) is obtained at 4% Mo-doping, which shows increases by 13% in Jsc and by 7% in η, as compared with the undoped DSSC.
차하림,손우성,( Suresh Thogiti ),( Rajesh Cheruku ),김재홍 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Enhancement of the charge transfer rate at the interfacial region in dye sensitized solar cells (DSSCs) is one of the most important criteria determining cell efficiency. Herein, we report a novel strategy for enhancing charge transfer between dye sensitized active layer and current collector by employing W-doped TiO<sub>2</sub> blocking layer. We propose the graded charge transport blocking layer with deposition W-TiO<sub>2</sub> thin film having different ECB at layer by layer for enhancing the diffusion coefficient and length with suppressing the probability of charge recombination. The graded blocking layer significantly increases the electron transfer rate at the interfacial region between the active layer and current collector. In particular, graded 1-5-7-9 W blocking layer exhibits highest photovoltaic performance of 11.54 % without decreasing VOC, which is 50 % higher than basic DSSCs without blocking layer.
Understanding of Mechanism and Enhanced Electron Mobility for the Bifacial Dye-sensitized Solar Cell
장유정,곽수정,( Suresh Thogiti ),김재홍 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
The mechanism and electron transfer rate of bifacial dye-sensitized solar cells was not fully understood yet, however the photovoltaic efficiency and IPCE of dye-sensitized solar cells enhanced, significantly. The bifacial DSSC was composed with two TiO<sub>2</sub> layers, a layer was used with the photo-electrode with photosensitizer, an another layer was used on the Pt counter-electrode which was absorbed different photosensitizer to absorb different wavelength of light that photosensitizer absorbed in the photo-electrode. We believe that the second layer of TiO<sub>2</sub> can act as the hole transfer layer from HOMO of the excited photosensitizer which can enhance the photovoltaic performance of DSSC.
Temperature dependent photovoltaic performance of DSSCs based on quasi-solid state redox couple
김우철,손창희,( Suresh Thogiti ),이도경,김재홍 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
The effect of temperature variations on the performance of dye-sensitized solar cells (DSSC), based on quasi-solid electrolyte, has been studied under 1 sun irradiance. The cell performance was characterized with J-V curves obtained at different cell operating temperatures and electrochemical impedance spectroscopy measurements before and after the temperature treatments. The measured temperature range was from ca. 25 °C to 75 °C at an interval of ca. 10 °C. The results show the higher temperature, the higher photo-current density of DSSCs. At lower temperatures, the short-circuit current (JSC) is limited by the conductivity of electrolyte, while at higher temperatures, the JSC increases due to more pronounced charge transport. Highest energy conversion efficiency of 7.93% was obtained at 55 °C, due to the gains in JSC and FF.
장유정,석승윤,( Suresh Thogiti ),( Rajesh Cheruku ),김재홍 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
The novel concept of introducing cascade structure into the photo-anode network with Metal-doped photo-electrode in dye-sensitized solar cells (DSSCs) such as W and Mo is proposed to increase the power conversion efficiency. An improvement in the device performance was obtained when layered metal-doped TiO2 films graded band structure were applied as the photo-anode of DSSCs. DSSCs containing the graded band structure engineered photo-electrode exhibited the significant enhanced photocurrent density and photovoltaic performance without decreasing the VOC, which is 50 % higher than basic DSSCs without a blocking layer. These findings suggest an innovative route toward the harvesting solar energy by enhancing the carrier charge transfer rate.