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Effect of Sulfur Doped TiO2 on Photovoltaic Properties of Dye-Sensitized Solar Cells
Hyunwoong Seo,남상훈,Naho Itagaki,Kazunori Koga,Masaharu Shiratani,부진효 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.4
In a dye-sensitized solar cell (DSC), a nano-porous semiconductor layerplays an important role in the performance. It determines open-circuitvoltage and it affects the dye adsorption capacity and charge transfer,which are closely associated with photocurrent and overall performance. TiO2 is the most proper material for nano-porous layer since the firstdevelopment of DSCs. This work focuses on the enhancement of TiO2by doping. Sulfur (S) doping enhances charge transfer and the photoconversionof TiO2. Therefore, the increase in photocurrent andefficiency is expected by S doping. S is doped into TiO2 by hydrolysismethod. The amount of S is varied and their photo-responses areverified. The most effective S doped TiO2 is applied to DSCs. Overallperformance of DSC is enhanced by the addition of S doped TiO2. Especially, the photocurrent is much increased by the improvement oncharge transfer, electron lifetime, and photo-conversion. The photovoltaicproperties of DSCs are investigated with various ratios of undoped and Sdoped TiO2. Finally, a DSC based on undoped and S doped TiO2 ratio of1:1 has the highest efficiency, better than that of a standard DSC basedon undoped TiO2.
Seo, Hyunwoong,Ichida, Daiki,Hashimoto, Shinji,Itagaki, Naho,Koga, Kazunori,Shiratani, Masaharu,Nam, Sang-Hun,Boo, Jin-Hyo American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.5
<P>The multiple exciton generation characteristics of quantum dots have been expected to enhance the performance of photochemical solar cells. In previous work, we first introduced Si quantum dot for sensitized solar cells. The Si quantum dots were fabricated by multi-hollow discharge plasma chemical vapor deposition, and were characterized optically and morphologically. The Si quantum dot-sensitized solar cells had poor performance due to significant electron loss by charge recombination. Although the large Si particle size resulted in the exposure of a large TiO2 surface area, there was a limit to ho much the particle size could be decreased due to the reduced absorbance of small particles. Therefore, this work focused on decreasing the internal impedance to improve charge transfer. TiO2 was electronically modified by doping with vanadium, which can improve electron transfer in the TiO2 network, and which is stable in the redox electrolyte. Photogenerated electrons can more easily arrive at the conductive electrode due to the decreased internal impedance. The dark photovoltaic properties confirmed the reduction of charge recombination, and the photon-to-current conversion efficiency reflected the improved electron transfer. Impedance analysis confirmed a decrease in internal impedance and an increased electron lifetime. Consequently, these improvements by vanadium doping enhanced the overall performance of Si quantum dot-sensitized solar cells.</P>
Seo, Hyunwoong,Gopi, Chandu V.V.M.,Kim, Hee-Je,Itagaki, Naho,Koga, Kazunori,Shiratani, Masaharu Elsevier 2017 ELECTROCHIMICA ACTA Vol.249 No.-
<P><B>Abstract</B></P> <P>Polymer nano-composite composed of poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) and TiO<SUB>2</SUB> nano-particles was deposited on fluorine-doped tin oxide substrate and applied as an alternative to Au counter electrode of quantum dot-sensitized solar cell (QDSC). It became surface-richer with the increase in nano-particle amount so that catalytic reaction was increased by widened catalytic interface. Electrochemical impedance spectroscopy and cyclic voltammetry clearly demonstrated the enhancement of polymer nano-composite counter electrode. A QDSC based on polymer nano-composite counter electrode showed 0.56V of V<SUB>OC</SUB>, 12.24mAcm<SUP>−2</SUP> of J<SUB>SC</SUB>, 0.57 of FF, and 3.87% of efficiency and this photovoltaic performance was higher than that of QDSC based on Au counter electrode (3.75%).</P> <P><B>Highlights</B></P> <P> <UL> <LI> We studied polymer nano-composite containing TiO<SUB>2</SUB> nano-particles as a catalyst. </LI> <LI> Polymer nano-composite was applied for quantum dot-sensitized solar cells. </LI> <LI> Polymer nano-composite catalyst was considerably improved with TiO<SUB>2</SUB> nano-particles. </LI> <LI> Polymer nano-composite showed higher photovoltaic performance than conventional Au. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Analysis on the Photovoltaic Property of Si Quantum Dot-Sensitized Solar Cells
Hyunwoong Seo,Daiki Ichida,Giichiro Uchida,Kunihiro Kamataki,Naho Itagaki,Kazunori Koga,Masaharu Shiratani 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
This work first introduced Si quantum dots (QDs) for QD-sensitized solar cells (QDSCs). However, the particle size of Si QDs, which had visible light absorption, was relatively large. The paint-type Si QDSC was proposed in this work because Si QDs could not penetrate into nano-porous TiO2 network. Si QDs were synthesized by multi-hollow plasma discharge CVD and mixed with TiO2 paste. For better performance, thickness of Si-TiO2 layer was varied by coating times and Si-TiO2 films were optically and electrically analyzed. As a result, 6 times screen printed Si-TiO2 film had the best performance with the smallest internal impedance and the highest photon to current efficiency.