Electrodeposited molybdenum selenide sheets on nickel foam as a binder-free electrode for supercapacitor application

Mariappan, Vimal Kumar,Krishnamoorthy, Karthikeyan,Pazhamalai, Parthiban,Sahoo, Surjit,Kim, Sang-Jae Elsevier 2018 ELECTROCHIMICA ACTA Vol.265 No.-

<P><B>Abstract</B></P> <P>Two-dimensional nanostructured metal chalcogenides have significant consideration as electrode materials for energy storage application owing to their fascinating properties. In this work, we have grown two-dimensional MoSe<SUB>2</SUB> sheets directly on the surface of nickel foam via facile one-step electrochemical deposition method and examined their use as a binder-free electrode for supercapacitor. The physicochemical characterizations such as X-ray diffraction, field emission scanning electron microscope, X-ray photoelectron spectrum, and Raman analysis confirmed the formation of MoSe<SUB>2</SUB> sheets on Ni foam. The effect of deposition time (5 and 10 min) on the electrochemical properties of the MoSe<SUB>2</SUB> sheets are examined in detail using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopic analyses, respectively. The cyclic voltammetry profiles confirmed that the charge-storage mechanism in MoSe<SUB>2</SUB> sheets is due to the ion intercalation/de-intercalation kinetics. A high specific capacity of 548 mAh g<SUP>−1</SUP> was obtained for the MoSe<SUB>2</SUB>/Ni electrode from CV profile measured using a scan rate of 5 mV s<SUP>−1</SUP>. The MoSe<SUB>2</SUB>/Ni electrode delivered a specific capacity of 325.92 mAh g<SUP>−1</SUP> from charge-discharge analysis obtained at constant discharge current density of 4 mA cm<SUP>−2</SUP> with good cyclic stability. The capacitive properties and the mechanism of charge-storage in the MoSe<SUB>2</SUB>/Ni electrode deposited at different time intervals were examined by the electrochemical impedance spectroscopy using Nyquist and Bode phase angle plot. The experimental results ensure that the MoSe<SUB>2</SUB>/Ni electrode might be used as the high-performance electrode for the next-generation energy storage devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A facile electrochemical deposition of MoSe<SUB>2</SUB> sheets on Ni foam was demonstrated. </LI> <LI> Field emission scanning electroscope confirms the growth of MoSe<SUB>2</SUB> sheet on Ni foam. </LI> <LI> Raman spectrum revealed the formation of few layered MoSe<SUB>2</SUB> sheets on Ni foam. </LI> <LI> The binder free MoSe<SUB>2</SUB> electrode delivered a high specific capacity of 548 mAh g<SUP>−1</SUP>. </LI> <LI> The MoSe<SUB>2</SUB>/Ni electrode shows excellent cyclic stability over 1000 cycles. </LI> </UL> </P>

MoSe2가 Cu(In,Ga)Se2 박막 태양전지 모듈의 ZnO/Mo 접합의 접촉 저항에 미치는 영향

조성욱,김아현,이경아,전찬욱 한국태양광발전학회 2020 Current Photovoltaic Research Vol.8 No.3

In this paper, the effect of MoSe2 on the contact resistance (RC) of the transparent conducting oxide (TCO) and Mo junction in the scribed P2 region of the Cu(In,Ga)Se2 (CIGS) solar module was analyzed. The CIGS/Mo junction becomes ohmic-contact by MoSe2, so the formation of the MoSe2 layer is essential. However, the CIGS solar module has a TCO/MoSe2/Mo junction in the P2 region due to structural differences from the cell. The contact resistance (RC) of the P2 region was calculated using the transmission line method, and MoSe2 was confirmed to increase RC of the TCO/Mo junction. B doped ZnO (BZO) was used as TCO, and when BZO/MoSe2 junction was formed, conduction band offset (CBO) of 0.6 eV was generated due to the difference in their electron affinities. It is expected that this CBO acts as a carrier transport barrier that disturbs the flow of current, resulting in increased RC. In order to reduce the RC caused by CBO, MoSe2 must be made thin in a CIGS solar module.

Quantification of the contact resistance of ZnO/MoSe2/Mo contact formed in a monolithic CIGS photovoltaic module

Sung-Wook Cho,A.-Hyun Kim,Gyeong-A. Lee,Chan-Wook Jeon 대한금속·재료학회 2021 ELECTRONIC MATERIALS LETTERS Vol.17 No.5

This study investigated the effect of MoSe2on the contact resistance (RC) of the transparent conducting oxide (TCO) andMo contact in the P2 region of the CIGS photovoltaic module. MoSe2formed in the process of making the Cu(In,Ga)Se2(CIGS) absorber layer imparts ohmic contact properties to the CIGS/Mo contact. In the process of connecting cells in seriesto fabricate a CIGS photovoltaic module, TCO/MoSe2/Mo contact was formed, and it was confirmed that MoSe2increasedthe RCof this contact using the transmission line method. It is estimated that the reason MoSe2increases the RCis due toconduction band offset (CBO). When ZnO used as TCO forms a contact with MoSe2,0.6 eV CBO is formed due to the differencein electron affinity. This CBO can act as a resistor that impedes the flow of current. Therefore, in order to reduce thecontact resistance of the CIGS solar module and increase the power conversion efficiency, it is necessary to make the MoSe2thin enough to facilitate carrier tunneling.

The electrical and valley properties of monolayer MoSe₂

Kim, Dong Hak,Lim, D. Elsevier 2017 CURRENT APPLIED PHYSICS Vol.17 No.2

<P>We studied the electrical, optical and valley properties of monolayer MoSe2. The measured PL circular polarization of monolayer MoSe2 was negligibly small, compared with the more-than 60% circular polarization of monolayer MoSe2. Doping-dependent PL measurement and Kelvin probe microscopy show that the small circular polarization because of its longer exciton lifetime in monolayer MoSe2. Furthermore, it is found that the longer exciton lifetime is due to the nearly intrinsic electrical property of monolayer MoSe2, where non-radiative trion decay, which is the dominant exciton decay mechanism in n-type monolayer MoSe2, is minimized due to the low density of excess electrons (holes). We believe that S and Se vacancies play an important role in determining the Fermi level position for these materials. Our experimental results show that monolayer MoSe2 can be a better valleytronics material than monolayer MoSe2 in spite of its small circular polarization. (C) 2016 Elsevier B.V. All rights reserved.</P>

Tuning Band Alignments and Charge-Transport Properties through MoSe₂ Bridging between MoS₂ and Cadmium Sulfide for Enhanced Hydrogen Production

Kumar, D. Praveen,Kim, Eun Hwa,Park, Hanbit,Chun, So Yeon,Gopannagari, Madhusudana,Bhavani, P.,Reddy, D. Amaranatha,Song, Jae Kyu,Kim, Tae Kyu American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.31

<P>Transition-metal dichalcogenide materials play a major role in the state-of-the-art innovations for energy conversion because of potential applications resulting from their unique properties. These materials additionally show inordinate potential toward the progress of hygienic power sources to deal with increasing environmental disputes at the time of skyrocketing energy demands. Herein, we report earth-abundant, few-layered, MoSe<SUB>2</SUB>-bridged MoS<SUB>2</SUB>/cadmium sulfide (CdS) nanocomposites, which reduce photogenerated electron and hole recombination by effectively separating charge carriers to achieve a high photocatalytic efficiency. Accordingly, the MoSe<SUB>2</SUB>-bridged MoS<SUB>2</SUB>/CdS system produced effective hydrogen (193 μmol·h<SUP>-1</SUP>) as that of water using lactic acid as a hole scavenger with the irradiation of solar light. The presence of few-layered MoSe<SUB>2</SUB> bridges in MoS<SUB>2</SUB>/CdS successfully separates photogenerated charge carriers, thereby enhancing the shuttling of electrons on the surface to active edge sites. To the best of our knowledge, this few-layered MoSe<SUB>2</SUB>-bridged MoS<SUB>2</SUB>/CdS system exhibits the most effective concert among altogether-reported MoS<SUB>2</SUB>-based CdS composites. Notably, these findings with ample prospective for the development of enormously real photocatalytic systems are due to their economically viable and extraordinary efficiency.</P> [FIG OMISSION]</BR>

Construction of dye-sensitized solar cells using wet chemical route synthesized MoSe2 counter electrode

Dhanasekaran Vikraman,Supriya A. Patil,Sajjad Hussain,Naveed Mengal,정성훈,정종완,박휘준,김학성,김현석 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.69 No.-

This paper presents a simple and large area wet chemical preparation route for molybdenum diselenide (MoSe2) atomic layers. MoSe2 was synthesized onto fluorine doped tin oxide substrates and could be directly used as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). The role of deposition time on the growth of MoSe2 CE was elaborately discussed using Raman, X-ray diffraction and photoluminescence studies. Influence of wet chemical growth time on the surface modification of MoSe2 CE was evidently demonstrated by scanning electron microscopy and atomic force microscopy studies. The MoSe2 CE electrode has lower charge transfer resistance and superior electrocatalytic activity towards triiodide/iodide redox behavior, comparable to conventional Pt CEs. High power conversion efficiency of 7.28% was achieved, equivalent to scarce noble metal Pt CE (7.40%). Uniform surface morphology with active edge sites highly dominated to promote the superior electrocatalytic activity. This work opens a way to use an economical wet chemical method to fabricate the layered MoSe2 CE as a replacement for high cost Pt based CE for DSSCs.

Photo-Electrical Properties of Trilayer MoSe2 Nanoflakes

Yang Hang,Qi Li,Wei Luo,Yanlan He,Xueao Zhang,GANG PENG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.7

The photo-electrical properties of trilayer MoSe2 nanoflakes, fabricated by mechanical exfoliation, were systematically studied in this paper. The trilayer MoSe2 nanoflakes are n-type and possess a high gate modulation (On/Off ratio is larger than 10 5) and a relatively high carrier mobility (1.79 cm2 V-1 s-1). The field effect transistor (FET) device of MoSe2 shows sensitive photo response, high photoresponsivity (Rλ = 26.2 mA/W), quick response time (t < 20 ms), high external quantum efficiency (η = 5.1%) and high detection rate (D = 2.7 x 10 9 W-1) for red and near-infrared wavelength. These results showed that the device based on few-layer MoSe2 nanoflakes exhibited good photo-electrical properties, which might open a new way to develop few-layer MoSe2-based material in the application of FETs and optoelectronics.

The electrical and valley properties of monolayer MoSe2

김동학,임대영 한국물리학회 2017 Current Applied Physics Vol.17 No.2

We studied the electrical, optical and valley properties of monolayer MoSe2. The measured PL circular polarization of monolayer MoSe2 was negligibly small, compared with the more-than 60% circular polarization of monolayer MoS2. Doping-dependent PL measurement and Kelvin probe microscopy show that the small circular polarization because of its longer exciton lifetime in monolayer MoSe2. Furthermore, it is found that the longer exciton lifetime is due to the nearly intrinsic electrical property of monolayer MoSe2, where non-radiative trion decay, which is the dominant exciton decay mechanism in n-type monolayer MoS2, is minimized due to the low density of excess electrons (holes). We believe that S and Se vacancies play an important role in determining the Fermi level position for these materials. Our experimental results show that monolayer MoSe2 can be a better valleytronics material than monolayer MoS2 in spite of its small circular polarization.

MO-N 박막의 셀렌화거동 및 이를 이용한 MOSE2 두께 제어

신혜진,전찬욱 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

본 연구에서는 후면 전극 Mo와 광흡수층 Cu(In,Ga)Se2 사이에 생기는 MoSe2에 주목하였다. 고온에 노출된 프리커서 계면에서 증기로 된 Se 기체와 Mo가 서로 반응하여 MoSe2층이 형성된다. 200nm 이하의 MoSe2층의 두께는 소자특성에 긍정적인 영향을 끼치는 반면 과도한 MoSe2층은 직렬 저항의 증가와 개방전압의 감소로 인해 태양전지 효율을 저하시킨다. 따라서 후면전극과 광흡수층 사이에 Mo-N 확산방지막을 증착하여 MoSe2층의 두께를 제어하고자 한다. Mo-N층을 가진 후면전극을 제작하여 과도한 MoSe2의 성장을 제어할 수 있는 확산 방지막 역할을 수행하는지 유무를 확인하기 위해 전기적 특성 및 안정성을 XRD, 4 point probe(4PP) 등으로 관찰해볼 예정이다.

High Performance MoSe₂/Mo Counter Electrodes Based- Dye-Sensitized Solar Cells

Hussain, Sajjad,Patil, Supriya A.,Vikraman, Dhanasekaran,Liu, Hailiang,Kim, Hak-Sung,Jung, Jongwan The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.2

<P>In the present study, multilayer MoSe2/Mo nanostructures fabricated by surface selenization of Mo-coated glass substrates using magnetron sputtering, was proposed as a counter electrode (CE) catalyst in dye-sensitized solar cells (DSSCs) to speed up the reduction of triiodide I-3(-) to iodide I-. The extensive cyclic voltammograms (CV) and Tafel curve analysis indicated that the current density of the optimized MoSe2/Mo CE was higher than Pt CEs due to the fast reduction species. Furthermore, the peak current densities of theMoSe(2)/Mo CE showed little degradation after consecutive 100 CV cycles, suggesting high electrochemical stability of the MoSe2/Mo CE. In addition, MoSe2/Mo CE exhibited lower charge-transfer resistance than Pt CEs. Finally, the DSSC assembled with the MoSe2/Mo CE showed a high power conversion efficiency of 9.57% under illumination of 100 mW.cm(-2) (DSSC with Pt CE: 9.15%). (C) 2017 The Electrochemical Society. All rights reserved.</P>