Enhancement of Photoelectric Efficiency in a Dye-sensitized Solar Cell Using Hollow TiO₂ Nanoparticles as an Overlayer

Lee, Kyoung-No,Kim, Woo-Byoung,Lee, Caroline Sunyong,Lee, Jai-Sung Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.6

$TiO_2$ hollow nanoparticles (HNPs) and their light scattering effect which influences on the photoelectric conversion efficiency of a dye-sensitized solar cell (DSSC) were investigated. When only HNPs were employed in DSSC as the anode layer material, the conversion efficiency (e.g., 0.96%) was the lowest, possibly due to scattering loss of incident light. However, DSSC fabricated by using HNPs as a scattering overlayer on the $TiO_2$ nanoparticles (P-25), showed higher conversion efficiency (4.02%) than that without using HNPs (3.36%).

Ti-doped hydrogenated diamond like carbon coating deposited by hybrid physical vapor deposition and plasma enhanced chemical vapor deposition

Lee, Na Rae,Jun, Yee Sle,Moon, Kyoung Il,Lee, Caroline Sunyong Institute of Pure and Applied Physics 2017 Japanese Journal of Applied Physics Vol. No.

<P>Diamond-like carbon films containing titanium and hydrogen (Ti-doped DLC: H) were synthesized using a hybrid technique based on physical vapor deposition (PVD) and plasma enhanced chemical vapor deposition (PECVD). The film was deposited under a mixture of argon (Ar) and acetylene gas (C2H2). The amount of Ti in the Ti-doped DLC: H film was controlled by varying the DC power of the Ti sputtering target ranging from 0 to 240W. The composition, microstructure, mechanical and chemical properties of Ti-doped DLC: H films with varying Ti concentrations, were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nano indentation, a ball-on-disk tribometer, a four-point probe system and dynamic anodic testing. As a result, the optimum composition of Ti in Ti-doped DLC: H film using our hybrid method was found to be a Ti content of 18 at. %, having superior electrical conductivity and high corrosion resistance, suitable for bipolar plates. Its hardness value was measured to be 25.6GPa with a low friction factor. (C) 2017 The Japan Society of Applied Physics</P>

Evaluation of Electrochromic Device Influenced by Various Formulation of Solid Polymer Electrolyte

Minji Lee,Minhee Son,Doo-Man Chun,Caroline Sunyong Lee 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.1

Electrochromic devices (ECDs) using various polymer electrolyte membranes were evaluated in relation to their optical and electrochemical properties. It was found that the composition of polymer matrix markedly influence the transmittance change (Δ T ) and stability of ECDs. The electrochromic (WO 3 ) and ion storage (Antimony tin oxide; ATO) layers were fabricated using dry deposition method. Moreover, various types of polymer matrix were used as the electrolyte, i.e., Liquid; PVdFHFP (UV-0); PEGDMA-PEGMA/PVdF-HFP blended (UV-30); and PEGDMA-PEGMA solid (UV-100) membranes. ECDs using UV-30 exhibited good cyclability, in which the Δ T of 35% was maintained over 200 cycles. Furthermore, as a result of electrochemical analysis, ECD using UV-30 showed charge density of 34.43 mC/cm 2 with low charge transfer resistance of 237.7 Ω at the interface between the coloration layer and electrolyte. Therefore, the solid polymer matrix electrolyte (UV-30) improved the electrochromic performance including stability due to excellent ion dissociation and ion mobility in the electrolyte.

Fabrication of transparent conductive tri-composite film for electrochromic application

Choi, Dahyun,Lee, Minji,Kim, Hyungsub,Chu, Won-shik,Chun, Doo-man,Ahn, Sung-Hoon,Lee, Caroline Sunyong Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.425 No.-

<P><B>Abstract</B></P> <P>A transparent conductive electrode (TCE) based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was developed using a dry deposition method for application as an electrochromic (EC) device. To improve its electrical conductivity and stable EC performance, AgNW and TiO<SUB>2</SUB> nanoparticles were included in the TCE film. The resulting TiO<SUB>2</SUB>/AgNW/PEDOT:PSS hybrid film showed electrical sheet resistivity of 23Ω/sq., similar to that of a commercial TCE film. When +2.0V was applied to the hybrid film, the response current was stable, maintaining a value of 2.0mA. We found that the hybrid film could be used as an EC device, without using commercial TCE film. Antimony-doped tin oxide on indium-doped tin oxide-glass as an ion-storage layer was combined with the hybrid film, with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) injected into the EC device as an ionic liquid electrolyte. The optical transmittance difference between the colored and bleached states was 23% at 630nm; under applied voltages of −2.0V and +2.0V, the coloration efficiency was 127.83cm<SUP>2</SUP>/C. Moreover, cyclic transmittance with switching voltage for 3h showed stable optical transmittance of 31% at 630nm. Cyclic voltammetry measurements indicated stable behavior over 50 cycles. Thus, the proposed TCE configuration (TiO<SUB>2</SUB>/AgNW/PEDOT:PSS) shows great potential as a substitute for commercial TCEs, the cost of which depends on the availability of rare-earth materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Tri-composite film composed of TiO<SUB>2</SUB>/AgNW/PEDOT:PSS for transparent conductive electrode (TCE),was developed to be used for electrochromic device. </LI> <LI> This Tri-composite film showed low electrical sheet resistivity, comparable to that of TCE and maintained stable response current with voltage application of +2.0V. </LI> <LI> This electrochromic device using ITO-free TCE, showed coloration efficiency of 127.83cm<SUP>2</SUP>/C. </LI> <LI> Dry deposited TiO2 film shows nanoporous <I>p</I>-<I>n</I> heterostructure to improve electrochemical performance of the device. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigation of dry-deposited ion storage layers using various oxide particles to enhance electrochromic performance

Choi, Dahyun,Lee, Minji,Kim, Hyungsub,Chu, Won-shik,Chun, Doo-man,Ahn, Sung-Hoon,Lee, Caroline Sunyong North-Holland 2018 Solar Energy Materials and Solar Cells Vol. No.

<P><B>Abstract</B></P> <P>Various ion storage layers were fabricated on ITO-glass substrates by a dry deposition process to study their effects in electrochromic devices. Dense nickel oxide (NiO) film was formed using micro-sized NiO particles, a porous film was formed using nano-sized NiO particles, and a porous antimony tin oxide (ATO) film was formed using nano-sized ATO particles. Electrochemical analyses revealed that the nano-porous NiO layer had a high charge capacity with a low charge transfer resistance. Moreover, an electrochromic device using a NiO film with nano-sized pores had an optical transmittance difference of 42% and a stable cyclic transmittance for 1h at a wavelength of 630nm. We assessed the effects of the different ion storage layers by evaluating the electrochromic device in terms of the following important properties: 1) high charge capacity, 2) low charge transfer resistance at the interface between film and electrolyte, and 3) high diffusion rate from film to electrolyte. Based on these criteria, we found that the ion storage layer formed with nano-sized NiO particles best satisfied these conditions. Finally, we confirmed that stable and high electrochromic performance can be achieved through improving these properties in ion storage layers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ion storage (IS) layer fabricated by dry deposition method using various sized NiO. </LI> <LI> NiO film resulting in nano-sized pores, showed high charge capacity with low transfer resistance. </LI> <LI> Device using Nano NiO film showed a transmittance difference of 42% with stable switching at 630nm. </LI> <LI> Stable and high electrochromic performance can be achieved by adding metal oxide based IS layers. </LI> </UL> </P>

Evaluation of V2O5 Film-Based Electrochromic Device with Dry-Deposited Ion Storage Layer

Dongwon Shin,Jiseon Kim,Caroline Sunyong Lee 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.1

Vanadium pentoxide (V2O5) film was used to fabricate an electrochromic device counterbalanced with a dry-deposited ion storage layer (ISL). For the ISL, a mixture of antimony-doped tin oxide (ATO) and Prussian blue (PB) powders (PB-ATO; 1:4 vol%) was dry deposited to form PB-ATO ISL as the counter electrode of the device, thereby improving electrochromic device characteristics. Dry deposition provided a film with a rough surface, which resulted in improved electrochromic properties because of the large surface area of the ISL, which provided more paths for electron movement. The ISL was deposited using a dry deposition system (i.e., the nanoparticle deposition system [NPDS]) to maximize the surface area of the film. The polyol method was used to fabricate V2O5 film with high crystallinity for better electrochromic properties. The fabricated V2O5-based electrochromic device (ECD) was evaluated by electrochemical analysis. Compared with the ECD without PB-ATO ISL, the difference in reflectance exceeded 50% for the ECD with PB-ATO ISL. Moreover, the ECD without ISL had a diffusion coefficient of 1.88 × 10−10 S2/s, while the ECD with PB-ATO ISL had an order of magnitude higher diffusion coefficient of 2.47 × 10−9 cm2/s. Therefore, the performance of the ECD was improved using dry-deposited ISL composed of PB-ATO. The coloration of the device was dramatically improved using PB-ATO ISL, compared with the device with ATO alone or without any ISL.

상압소결법으로 제조된 경사기능재료의 형상 예측

이재철(Jae-Chul Lee),안성훈(Sung-Hoon Ahn),조동국(Dong-Guk Cho),이선영(Caroline Sunyong Lee) (사)한국CDE학회 2010 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2010 No.1

The final goal of this research is the precise fabrication of functionally graded material (FGM) based on nickel and alumina using pressureless sintering method. Deformation of specimen during the manufacturing process has to be predicted and controlled for the goal. In this paper, a interpolation model based on experimental shrinkage data of 4 layers from the 11 layered FGM was proposed to predict the shrinkage of the other layers. Temperature dependent elastic modulus was investigated by literatures, and elastic modulus of nickel on 1350℃ was selected with 3 cases to verify a phenomenon of liquid fraction increase in only 100% nickel. Deformed shape after sintering was predicted by proposed interpolation model, selected properties, and finite element method. The predicted results were compared with measurement data of fabricated FGM for verification of the phenomenon. And it was verified that liquid fraction of only 100% nickel on 1350℃ was increased through the numerical result.

Crack-Free Joint in a Ni-Al₂O₃ FGM System Using Three-Dimensional Modeling

Park, Jong Ha,Lee, Jae Chul,Ryu, Sae Hee,Jung, Kyu Bong,Song, Han-Bok,Yun, Joon Chul,Choa, Yong Ho,Ahn, Sung Hoon,Lee, Caroline Sunyong The Japan Institute of Metals 2009 MATERIALS TRANSACTIONS Vol.50 No.7

<P>With the recent emphasis on the importance of successfully joining materials, researchers have tried to join metals and ceramics with different coefficients of thermal expansion (CTEs) by using the functionally graded material (FGM) method. This involves inserting interlayers with composition gradients that range from one material to the other, thereby minimizing the stress caused by differences in CTE values. In this study, the FGM that included 10 layers of Ni-Al<SUB>2</SUB>O<SUB>3</SUB> with eight inter-layers was studied. Previous studies have focused on controlling the composition of inter-layers and optimizing the dispersion process to prevent cracks. Thermal stress was reduced by varying the weights of the inter-layers and increasing the green-body density by using several powder sizes. The powders were well-dispersed during fabrication by using simultaneous dispersion and dry processes followed by a cold isostatic press (CIP) and pressure-less sintering in an inert atmosphere. As a result, a crack-free Ni-Al<SUB>2</SUB>O<SUB>3</SUB> FGM joint was obtained. The residual stress in each layer was calculated to predict cracks using ANSYS simulation and maximum principal stress criterion; experimental values matched simulation results. In addition, an oriented Vickers indentation test was used to assess the quality of the joint. Crack-paths were not deflected across the interface, indicating good bond strength between interfaces. Sample density was measured using the Archimedes method; the sintered joint was less dense than its theoretical density but was denser than the results obtained by using previous methods.</P>

Synthesis of CdS with Graphene by CBD(Chemical Bath Deposition) Method and Its Photocatalytic Activity

Pawar, R.C.,Lee, Jin-Yong,Kim, Eun-Jeong,Kim, Hyungsub,Lee, Caroline Sunyong Materials Research Society of Korea 2012 한국재료학회지 Vol.22 No.10

Synthesis of RGO (reduced graphene oxide)-CdS composite material was performed through CBD (chemical bath deposition) method in which graphene oxide served as the support and Cadmium Sulfate Hydrate as the starting material. Graphene-based semiconductor photocatalysts have attracted extensive attention due to their usefulness for environmental and energy applications. The band gap (2.4 eV) of CdS corresponds well with the spectrum of sunlight because the crystalline phase, size, morphology, specic surface area and defects, etc., of CdS can affect its photocatalytic activity. The specific surface structure (morphology) of the photocatalyst can be effective for the suppression of recombination between photogenerated electrons and holes. Graphene (GN) has unique properties such as a high value of Young's modulus, large theoretical specific surface area, excellent thermal conductivity, high mobility of charge carriers, and good optical transmittance. These excellent properties make GN an ideal building block in nanocomposites. It can act as an excellent electron-acceptor/transport material. Therefore, the morphology, structural characterization and crystal structure were observed using various analytical tools, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. From this analysis, it is shown that CdS particles were well dispersed uniformly in the RGO sheet. Furthermore, the photocatalytic property of the resulting RGO-CdS composite is also discussed in relation to environmental applications such as the photocatalytic degradation of pollutants. It was found that the prepared RGO-CdS nanocomposites exhibited enhanced photocatalytic activity as compared with that of CdS nanoparticles. Therefore, better efficiency of photodegradation was found for water purification applications using RGO-CdS composite.

캔틸레버형 광 정보저장에서의 빠른 팁/매체 간극제어를 위한 팁/구동기의 동역학적 분석

이성규(Sung-Q LEE),송기봉(KI-Bong SONG),김준호(Jun-Ho KIM),김은경(Eun-Kyung KIM),박강호(Kang-Ho PARK),남효진(Hyo-Jin NAM),이선영(Caroline Sunyong LEE),김영식(Young-Sik KIM) 한국소음진동공학회 2003 한국소음진동공학회 학술대회논문집 Vol.2003 No.5