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Sinha, Soumyadeep,Ramasamy, Hari Vignesh,Nandi, Dip K.,Didwal, Pravin N.,Cho, Jae Yu,Park, Chan-Jin,Lee, Yun-Sung,Kim, Soo-Hyun,Heo, Jaeyeong The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.34
<P>In addition to their optoelectronic applications, Zn-based oxides and sulfides have also been widely studied as electrode materials in Li-ion batteries owing to their high theoretical capacity. However, both the materials suffer from a drastic loss in capacity due to their poor conductivity and electrochemical instability. A very efficient and carefully controlled combination of these two may address these limitations. In this work, thin films of zinc oxysulfide (ZnOS) with an O/(O + S) ratio of ∼0.7 were deposited using a combination of oxide and sulfide atomic layer deposition (ALD) cycles; they were then tested as anodes in Li-ion batteries. The material was grown directly on a stainless steel substrate (SS), characterized extensively using several <I>ex situ</I> characterization tools, and then used as an anode with no binder or conductive additives. Cyclic voltammetry measurements were used to confirm the reversible conversion of ZnOS in addition to the well-known alloying-dealloying Li-Zn reaction. The material loading was further optimized by varying the number of ALD supercycles to attain the maximum stable cycling performance. The highest stable capacities of 632.9 and 510.3 mA h g<SUP>−1</SUP> were achieved at current densities of 0.1 and 1 A g<SUP>−1</SUP> (∼4 and 40 μA cm<SUP>−2</SUP>), respectively, for a ZnOS film with an optimum thickness of ∼75 nm. The optimized ZnOS anode exhibited superior electrochemical performance in comparison to the equivalent pristine ZnO and ZnS anodes. Finally, the post-cycling analysis of the binder-free ALD grown ZnOS anodes demonstrated excellent adhesion to the SS substrate and the high stability of these films upon cycling.</P>
Sinha, Soumyadeep,Nandi, Dip K.,Kim, Soo-Hyun,Heo, Jaeyeong North-Holland 2018 Solar Energy Materials and Solar Cells Vol. No.
<P><B>Abstract</B></P> <P>Atomic layer deposition (ALD) is not just a thin film deposition technology limited to the semiconductor IC industries to grow high-<I>k</I> gate dielectric or a Cu diffusion barrier layer. In recent times, it has found plenty of applications in the field of renewable energy due to its precise thickness control up to few angstroms and its unique feature of conformal and uniform coating on any randomly shaped 3D structure. ALD has far-reaching applications in this field, including electrochemical storage, fuel cells, solar photovoltaics (PV), and catalysis for water splitting to produce H<SUB>2</SUB> as a green fuel. In solar PV technology, ALD is now being extensively used as an efficient tool to deposit surface passivation layers, absorber or sensitizer, transparent conducting oxide, and barrier and buffer layers in several kinds of solar cells. Out of all the different layers associated with a solar cell, ALD is majorly used for the development of a very thin <I>n-</I>type buffer layer. This review article presents a systematic chronological study on such ALD-grown buffer layers for thin film solar cells (TSFCs). The study is carried out in detail based on different earth-abundant absorber materials, such as Cu<SUB>2</SUB>ZnSn(S,Se)<SUB>4</SUB> (CZTSSe), Cu<SUB>2</SUB>O and SnS, for which ALD is successfully used to deposit the buffer layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ALD buffer layers for TFSCs based on emerging absorbers are reviewed. </LI> <LI> Correlation between cell performance and ALD process parameters is investigated. </LI> <LI> Progress on the efficiency of the TFSCs based on ALD buffers is reported. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Ramasamy, Hari Vignesh,Sinha, Soumyadeep,Park, Jooyeon,Gong, Minkyung,Aravindan, Vanchiappan,Heo, Jaeyeong,Lee, Yun-Sung The Korean Electrochemical Society 2019 Journal of electrochemical science and technology Vol.10 No.2
Ni-rich layered oxides $Li(Ni_xCo_yMn_z)O_2$ (x + y + z = 1) have been extensively studied in recent times owing to their high capacity and low cost and can possibly replace $LiCoO_2$ in the near future. However, these layered oxides suffer from problems related to the capacity fading, thermal stability, and safety at high voltages. In this study, we use surface coating as a strategy to improve the thermal stability at higher voltages. The uniform and conformal $Al_2O_3$ coating on prefabricated electrodes using atomic layer deposition significantly prevented surface degradation over prolonged cycling. Initial capacity of 190, 199, 188 and $166mAh\;g^{-1}$ is obtained for pristine, 2, 5 and 10 cycles of ALD coated samples at 0.2C and maintains 145, 158, 151 and $130mAh\;g^{-1}$ for high current rate of 2C in room temperature. The two-cycle $Al_2O_3$ modified cathode retained 75% of its capacity after 500 cycles at 5C with 0.05% capacity decay per cycle, compared with 46.5% retention for a pristine electrode, at an elevated temperature. Despite the insulating nature of the $Al_2O_3$ coating, a thin layer is sufficient to improve the capacity retention at a high temperature. The $Al_2O_3$ coating can prevent the detrimental surface reactions at a high temperature. Thus, the morphology of the active material is well-maintained even after extensive cycling, whereas the bare electrode undergoes severe degradation.
Nandi, Dip K.,Sahoo, Sumanta,Sinha, Soumyadeep,Yeo, Seungmin,Kim, Hyungjun,Bulakhe, Ravindra N.,Heo, Jaeyeong,Shim, Jae-Jin,Kim, Soo-Hyun American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.46
<P>This article takes an effort to establish the potential of atomic layer deposition (ALD) technique toward the field of supercapacitors by preparing molybdenum disulfide (MoS2) as its electrode. 'While molybdenum hexacarbonyl [Mo(CO)(6)] serves as a novel precursor toward the low temperature 'synthesis of ALD-grown MoS2, H2S plasma helps to deposit its polycrystalline phase at 200 degrees C. Several ex situ characterizations such as X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and so forth are performed in detail to study the as-grown MoS2 film on a Si/SiO2 substrate. While stoichiometric MoS2 with very negligible amount of C and O impurities was evident from XPS, the XRD and high-resolution transmission electron microscopy analyses confirmed the (002)-oriented polycrystalline h-MoS2 phase of the as-grown film. A comparative study of ALD-grown MoS2 as a supercapacitor electrode on 2-dimensional stainless steel and on 3-dimensional (3D) Ni-foam substrates clearly reflects the advantage and the potential of ALD for growing a uniform and conformal electrode material on a 3D-scaffold layer. Cyclic voltammetry measurements showed both double-layer capacitance and capacitance contributed by the faradic reaction at the MoS2 electrode surface. The optimum number of ALD cycles was also found out for achieving maximum capacitance for such a MoS2@3D-Ni-foam electrode. A record high areal capacitance of 3400 mF/cm(2) was achieved for MoS2@3D-Ni-foam grown by 400 ALD cycles at a current density of 3 mA/cm(2). Moreover, the ALD-grown MoS2@3D-Ni-foam composite also retains high areal capacitance, even up to a high current density of 50 mA/cm(2). Finally, this directly grown MoS2 electrode on 3D-Ni-foam by ALD shows high cyclic stability (>80%) over 4500 charge discharge cycles which must invoke the research community to further explore the potential of ALD for such applications.</P>
Song, Gwang Yeom,Oh, Chadol,Sinha, Soumyadeep,Son, Junwoo,Heo, Jaeyeong American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.28
<P>Atomic layer deposition was adopted to deposit VOx thin films using vanadyl tri-isopropoxide {VO[O-(C3H7)](3), VTIP} and water (H2O) at 135 degrees C. The self-limiting and purge-time-dependent growth behaviors were studied by ex situ ellipsometry to determine the saturated growth conditions for atomic-layer-deposited VOx. The as deposited films were found to be amorphous. The structural, chemical, and optical properties of the crystalline thin films with controlled phase formation were investigated after postdeposition annealing at various atmospheres and temperatures. Reducing and oxidizing atmospheres enabled the formation of pure VO2 and V2O5 phases, respectively. The possible band structures of the crystalline VO2 and V2O5 thin films were established. Furthermore, an electrochemical response and a voltage-induced insulator-to-metal transition in the vertical metal-vanadium oxide-metal device structure were observed for V2O5 and VO2 films, respectively.</P>
이원계 칼코지나이드 소재 기반 박막 태양전지 연구 동향
임동하,이다정,조재유,신경록,Man Hieu Tran,Soumyadeep Sinha,허재영 한국태양광발전학회 2017 한국태양광발전학회지 Vol.3 No.3
최근 들어 환경오염 문제와 화석에너지 자원 고갈로 인해 친환경적인 청정에너지 개발에 대한 중요성이 지속적으로 증대되고 있다. 태양광 기술은 다양한 장점에도 불구하고 아직까지 보급 확대 수준이 미미한데, 이는 기존 화석연료 기반 발전방식에 비해 발전단가의 경제성이 확보되지 않았기 때문이다. 본 원고에서는 이러한 발전단가를 낮추기 위해 이루어지고 있는 연구의 일례로서 SnS와 Sb₂Se₃ 중심의 이원계 칼코지나이드(binary chalcogenides) 원소 기반 박막태양전지 연구 동향을 알아보고자 한다.
Tran, Man Hieu,Cho, Jae Yu,Sinha, Soumyadeep,Gang, Myeng Gil,Heo, Jaeyeong Elsevier 2018 THIN SOLID FILMS - Vol.661 No.-
<P><B>Abstract</B></P> <P>The electrodeposited Cu<SUB>2</SUB>O thin films, with a controlled morphology, were obtained by varying the deposition parameters, such as the solution temperature, applied current and charge. An optimal deposition condition was achieved for a better quality Cu<SUB>2</SUB>O film which was favorable as an absorber layer for thin-film solar cell application. The effect of applied negative charge on the as-deposited Cu<SUB>2</SUB>O films was investigated, resulting in an increase in film thickness with increasing applied charge. The performance of the Cu<SUB>2</SUB>O/ZnO heterojunction solar cells with different Cu<SUB>2</SUB>O absorber thickness exhibited the highest power-conversion efficiency of 0.52%. Thicker Cu<SUB>2</SUB>O was beneficial for the decreased shunt conductance, but it also led to the increased series resistance. The optimal thickness of Cu<SUB>2</SUB>O absorber was ~3.3 μm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrodeposited Cu<SUB>2</SUB>O absorber layer with controlled morphology is achieved. </LI> <LI> An optimized deposition temperature exhibits highly uniform film deposition. </LI> <LI> ALD-ZnO films are used to from the Cu<SUB>2</SUB>O/ZnO TFSCs. </LI> <LI> Performance of TFSCs is highly dependent on the thickness of Cu<SUB>2</SUB>O absorber. </LI> <LI> A maximum PCE of 0.52% is achieved with optimal Cu<SUB>2</SUB>O thickness of 3.3 μm. </LI> </UL> </P>