Facile Electrochemical Synthesis of Manganese Cobalt Sulfide Counter Electrode for Quantum Dot-Sensitized Solar Cells

Vijayakumar, Elayappan,Kang, Soon- Hyung,Ahn, Kwang-Soon The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.5

<P>We have reported the formation of a thin manganese cobalt sulfide (MCS) film on a fluorine-doped SnO2 (FTO) substrate by a facile electrodeposition method for fabricating quantum-dot-sensitized solar cells (QDSSCs). The resulting FTO/MCS films are subsequently employed as counter electrodes (CEs) for cadmium selenide-based QDSSCs. The QDSSC with the FTO/MCS CE provided significantly enhanced short circuit current and fill factor, resulting in very high overall energy conversion efficiency (3.22%) compared to that with the Pt CE (1.08%) under 1-sun illumination. This can be attributed to the significantly enhanced electrocatalytic activity and superior electrical conductivity of the binary transition metal sulfide in addition to the excellent electrical contact at the interface between the electrodeposited MCS film and the FTO. Furthermore, the FTO/MCS exhibit excellent electrochemical stability, unlike the conventional Pt CE. These findings suggest that FTO/MCS should be a promising electrocatalytic electrode material for practical energy conversion applications. (C) 2018 The Electrochemical Society.</P>

Development of Tungsten Trioxide Using Pulse and Continuous Electrodeposition and Its Properties in Electrochromic Devices

Vijayakumar, Elayappan,Yun, Yong-Han,Quy, Vu Hong Vinh,Lee, Young-Hoon,Kang, Soon-Hyung,Ahn, Kwang-Soon,Lee, Seung Woo Electrochemical Society 2019 Journal of the Electrochemical Society Vol.166 No.4

<P>To develop an economical, efficient, and highly stable electrode having high transmittance modulation, thin films of tungsten trioxide (WO<SUB>3</SUB>) were deposited on an Indium-doped tin oxide (ITO) glass substrate by using simple one-step pulse voltage electrodeposition (PVE) and continuous voltage electrodeposition (CVE) routes. Electrochemical and optical analyses demonstrated that the WO<SUB>3</SUB> electrode prepared by PVE possessed high switching speed, high coloration efficiency, and excellent cyclic stability. Moreover, its stable performance in the colored state extended for a long duration even after the voltage was cutoff. The coloration efficiency values were determined to be 69.00 and 43.00 cm<SUP>2</SUP>/C for W-PVE-600s and W-CVE-200s, respectively. The excellent electrochemical and electrochromic properties were mainly attributed to large surface area of W-PVE-600s, which facilitated charge transfer and promoted insertion/exertion of H<SUP>+</SUP> ions in electrolytes better than the WO<SUB>3</SUB> electrode prepared by conventional methods. The significant electrocatalytic activity and stable performance have proved that the proposed W-PVE-600s film can be an alternative to conventional electrodes used in smart window technology applications.</P>

Enhanced Electrocatalytic Activity of Cu₂S-Polyaniline Heterostructure Counter Electrode for Quantum Dot-Sensitized Solar Cells

Vijayakumar, Elayappan,Quy, Vu Hong Vinh,Kwon, JongMyeong,Chae, Jiyoung,Kim, Jae-Hong,Kang, Soon-Hyung,Kim, Hyunsoo,Ahn, Kwang-Soon Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.12

<P>The Cu2S-Polyaniline (Cu-P) counter electrode (CE) was prepared by electropolymerization of polyaniline (PANI) on a FTO/Cu2S film. The surface morphology and crystallinity of the counter electrode were examined. The FTO/Cu-P CE provided significantly enhanced electrochemical activity and a faster charge transfer rate compared to the platinum (Pt), Cu2S, PANI, and PANI-Cu2S (P-Cu) CEs because of the synergistic effect between the high carrier mobility of PANI and the good electrocatalytic activity of Cu2S on the polysulfide electrolyte. Besides, the FTO/Cu-P CE exhibited excellent electrochemical stability, due to the strong interaction between the metal particles and electronegative nitrogen of PANI. The quantum dot-sensitized solar cell (QDSSC) with the FTO/Cu-P heterostructure CE exhibited a higher energy conversion efficiency (4.12%) than those with Pt (1.85%), Cu2S (3.71%), PANI (0.77%), and PANI-Cu2S (P-Cu) (1.01%) CEs. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Composite paste based on PbSe nanoparticles and carbon black thin film counter electrode for cadmium selenide quantum dot-sensitized solar cells

윤용한,( Elayappan Vijayakumar ),( Vu Hong Vin Quy ),채지영,이영훈,안광순 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

QDSSCs are designed based on the interfacial charge separation between a short band gap (donor) and a large band gap (acceptor) semiconductor. Polysulfide electrolyte and Pt counter electrode are the most commonly used in QDSSCs. However, the Pt-based counter electrode shows reduced activity in the polysulfide electrolyte due to poisoning effect. In this study, PbSe/Carbon Black (CB) composite electrode has been fabricated from pre-synthesized PbSe nanoparticles and Carbon Black with assist of PVDF as binder material by doctor-blading. Additionally, to enhance contact properties of composite film to FTO, post thermal treatment was done at Ar ambient. PbSe NPs/CB exhibited much higher catalytic property with polysulfide electrolyte than Pt. QDSSC with composite counter electrode achieved a power conversion efficiency 4.275% which is higher than Pt counter electrodes.

Electrodeposited MoS₂ as electrocatalytic counter electrode for quantum dot- and dye-sensitized solar cells

Quy, Vu Hong Vinh,Vijayakumar, Elayappan,Ho, Phuong,Park, Jeong-Hyun,Rajesh, John Anthuvan,Kwon, JongMyeong,Chae, Jiyoung,Kim, Jae-Hong,Kang, Soon-Hyung,Ahn, Kwang-Soon Elsevier 2018 ELECTROCHIMICA ACTA Vol.260 No.-

<P><B>Abstract</B></P> <P>Molybdenum disulfide (MoS<SUB>2</SUB>) films are electrochemically synthesized on F-doped SnO<SUB>2</SUB> (FTO) substrates using potentiostatic electrodeposition (ED) at a constant −1 V for 20–60 min. The MoS<SUB>2</SUB> is deposited according to island growth mode. As the ED time increases to 40 min, the clusters of MoS<SUB>2</SUB> nano particles enlarge and thicken, but maintain nanopores between the clusters. Additional increase in ED time (to 60 min) causes clusters to merge and make the film denser. Furthermore, this MoS<SUB>2</SUB> film exhibits cracks due to stress accumulated in the film. The film FTO/MoS<SUB>2</SUB> (40 min) shows significantly enhanced electrocatalytic activity compared to other films. This is because the FTO/MoS<SUB>2</SUB> (40 min) not only has more electrochemically active sites but also significantly facilitates charge transfer and mass transport. When it is employed as the counter electrode (CE) for quantum-dot and dye-sensitized solar cells (QD-SSC, D-SSC), the QD-SSC with FTO/MoS<SUB>2</SUB> (40 min) CE exhibits even higher overall energy conversion cell efficiency (3.69%) than that with Pt CE (2.16%). Moreover, the D-SSC with FTO/MoS<SUB>2</SUB> (40 min) CE exhibits cell efficiency (7.16%) similar to that with FTO/Pt CE (7.48%). This indicates that MoS<SUB>2</SUB> is a promising CE for all QD-SSCs and D-SSCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoS<SUB>2</SUB> films were electrochemically synthesized on F-doped SnO<SUB>2</SUB> substrates. </LI> <LI> Change in electrodeposition time affected particle size and pore condition. </LI> <LI> FTO/MoS<SUB>2</SUB> -ED 40 min had better electrocatalytic activity and more active sites. </LI> <LI> FTO/MoS<SUB>2</SUB> -40 also showed much improved charge transfer and mass transport. </LI> <LI> FTO/MoS<SUB>2</SUB>-40 CEs in QD-SSC and D-SSC showed better efficiency than Pt CE. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Preparation of copper sulfide electrocatalyst using electrodeposited Cu-Zn alloy for quantum dot-sensitized solar cells

채지영,( Vu Hong Vinh Quy ),( Elayappan Vijayakumar ),( Anthuvan Rajesh ),안광순 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Quantum dot-sensitized solar cells (QDSSCs) are a reliable renewable energy source. A QDSSC is assembled with the components in the following order: FTO/TiO2/QD/polysulfide electrolyte/CE/FTO. Recently, multiple efforts have been made to increase the power conversion efficiency of by modifying the materials by optimize chemical and physical properties. In QDSSCs, the counter electrodes (CEs) plays a key role in completing the electrical circuit and in the regeneration of sulfur redox couple through a reduction process. Among the CE materials, copper(I) sulfide (Cu2S) is a promising alternative to Pt CE, primarily due to its favorable electrochemical properties in the S2-/Sn2- redox couple, low cost, and high stability compared to other. In this study, we have reported Cu2S CE deposited Cu-Zn alloy on FTO and removed Zn using HCl after sulfurization. We simply increased surface area of CEs by removing Zn. These samples exhibited better electrocatalytic activity than FTO/Cu2S CEs.

Preparation of nickel selenide by pulsed-voltage electrodeposition and its application as a highly-efficient electrocatalyst at counter electrodes of quantum-dot sensitized solar cells

Lee, Young-Hoon,Yun, Yong-Han,Hong Vinh Quy, Vu,Kang, Soon-Hyung,Kim, Hyunsoo,Vijayakumar, Elayappan,Ahn, Kwang-Soon Elsevier 2019 ELECTROCHIMICA ACTA Vol.296 No.-

<P><B>Abstract</B></P> <P>We fabricate the nickel selenide thin films on fluorine-doped tin oxide conducting glass subtract using pulsed-voltage electrodeposition method for counter electrodes in quantum-dot-sensitized solar cells. The novelty of this work is nickel selenides are prepared by PVE significantly differs from the traditional continuous-voltage electrodeposition in morphology, compositions, and electrocatalytic activities. In general, NiSe<SUB>2</SUB>-PVE films consist of clusters with crystalline NiSe<SUB>2</SUB> nanoparticles which remain nanoporous because application of anodic bias during pulsed electrodeposition enables diffusion layer of H<SUB>2</SUB>SeO<SUB>3</SUB> recover from the deposition. The subsequent short cathodic bias not only facilitates new nucleation of nickel selenide but also hinders grain growth. In contrast, Ni<SUB>3</SUB>Se<SUB>2</SUB>-CVE film consists dense larger Ni<SUB>3</SUB>Se<SUB>2</SUB> grains with surface microcracks attributed to continuous grain growth and accumulated film stress. Hence, NiSe<SUB>2</SUB>-PVE enhances electrocatalytic activity in polysulfide electrolyte in an effective manner when compare to Ni<SUB>3</SUB>Se<SUB>2</SUB>-CVE, owing to significantly more electrocatalytic active sites and enhance charge and mass transports. As an outcome, QDSSC with NiSe<SUB>2</SUB>-PVE CE achieve significantly higher power conversion efficiency of 4.46% than those of cells with Pt (2.62%) and Ni<SUB>3</SUB>Se<SUB>2</SUB>-CVE (2.63%) CEs. Furthermore, electrochemical stability in polysulfide electrolyte medium is reasonably high.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nickel selenide prepared by pulse-voltage electrochemical deposition (NiSe<SUB>2</SUB>-PVE). </LI> <LI> NiSe<SUB>2</SUB>-PVE provides nanoporous clusters with uncracked NiSe<SUB>2</SUB> nanocrystals. </LI> <LI> NiSe<SUB>2</SUB>-PVE shows excellent electrocatalytic activity and stability. </LI> <LI> QDSSC with FTO/NiSe<SUB>2</SUB>-PVE CE exhibits significantly enhanced cell performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhanced electrocatalytic activity and electrochemical stability of copper(I) sulfide electrode electrodeposited on a Ti interlayer-coated fluorine-doped tin oxide substrate and its application to quantum dot-sensitized solar cells

Chae, Jiyoung,Oh, Munsik,Quy, Vu Hong Vinh,Kwon, JongMyeong,Kim, Jae-Hong,Kang, Soon-Hyung,Kim, Hyunsoo,Vijayakumar, Elayappan,Ahn, Kwang-Soon Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-

<P><B>Abstract</B></P> <P>Copper(I) sulfide (Cu<SUB>2</SUB>S) films are deposited on 15 nm-thick Ti (Titania) interlayer-coated fluorine-doped tin oxide (FTO) substrates. This is performed using potentiodynamic electrodeposition at selective numbers of cycles (10−20) in the potential range of −0.7 V to −0.2 V (vs. Ag/AgCl), followed by sulfurization. The results of Cu<SUB>2</SUB>S films on the FTO/Ti substrates are subsequently employed as counter electrodes for cadmium selenide quantum dot-sensitized solar cells (QDSSC). The Ti interlayer facilitates the Cu (copper) nucleation, during the Cu electrodeposition and leads to side-by-side packing of small Cu<SUB>2</SUB>S nanosheets after sulfurization. In contrast, conventional Cu<SUB>2</SUB>S grown on the FTO consists of a mixture of large and small Cu<SUB>2</SUB>S nanosheets. The distinct nanostructure of the FTO/Ti/Cu<SUB>2</SUB>S counter electrodes enhances the electrocatalytic activity and electrochemical stability comparing to those of FTO/Pt (Platinum) and FTO/Cu<SUB>2</SUB>S films. This is due to the increased number of electrochemically active sites, fast ion transport in the Cu<SUB>2</SUB>S nanosheets perpendicular to the substrate, and good adhesion to the Ti interlayer. The optimized FTO/Ti/Cu<SUB>2</SUB>S electrode, deposited in 15 cycles, contributes to significantly increase the cell efficiency (4.11%) of the QDSSC, resulting in 140% and 35.2% performances improvements for the QDSSCs with the Pt (1.71%) and FTO/Cu<SUB>2</SUB>S (3.04%) counter electrodes, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu<SUB>2</SUB>S prepared by electrochemical deposition on Ti interlayer-coated FTO. </LI> <LI> Ti interlayer facilitates the uniform Cu nucleation growth with small size. </LI> <LI> FTO/Ti/Cu<SUB>2</SUB>S (15 cycle) show excellent electrocatalytic activity and stability. </LI> <LI> QDSSC with the FTO/Ti/Cu<SUB>2</SUB>S exhibits significantly enhanced cell performance. </LI> </UL> </P>