Fabrication of Cu₂(Zn_<i>x</i>Mg_1-<i>x</i>)SnS₄ thin films by pulsed laser deposition technique for solar cell applications

Agawane, G.L.,Vanalakar, S.A.,Kamble, A.S.,Moholkar, A.V.,Kim, J.H. Elsevier 2018 Materials science in semiconductor processing Vol.76 No.-

<P>In this study, the pulsed laser deposition technique was applied for the preparation and characterization of Cu-2(ZnxMg1-x)SnS4 (CZMTS) thin films for solar cell applications. The effects of various zinc/magnesium compositional ratios on the properties of the CZMTS thin films were investigated. The field emission scanning electron microscopy studies revealed that the CZMTS thin films exhibited dense, uniform and smooth surfaces. The X-ray diffraction studies on the as-deposited and annealed CZMTS thin films showed the prominent peak from the (112) plane for kesterite phase Cu2ZnSnS4. The Raman studies on the CZMTS thin films further confirmed formation of kesterite phase and beneficial MoS2 layer. Further, the Hall measurement studies on CZMTS thin films confirmed p-type electrical conductivity behavior. The conductivity increased from 2.31 S/cm to 7.98 S/cm with increased Mg concentration. The X-ray energy dispersive spectroscopy studies revealed formation of stoichiometric thin films. The direct optical band gap for the CZMTS thin films were found to be in the range of 1.3-1.5 eV, suggesting their potential application as a low cost and earth abundant thin film solar cell absorber material.</P>

A review on pulsed laser deposited CZTS thin films for solar cell applications

Vanalakar, S.A.,Agawane, G.L.,Shin, S.W.,Suryawanshi, M.P.,Gurav, K.V.,Jeon, K.S.,Patil, P.S.,Jeong, C.W.,Kim, J.Y.,Kim, J.H. Elsevier 2015 JOURNAL OF ALLOYS AND COMPOUNDS Vol.619 No.-

<P><B>Abstract</B></P> <P>Cu<SUB>2</SUB>ZnSnS<SUB>4</SUB>; commonly abbreviated as CZTS is a promising material for low cost thin film solar cells, because of its suitable band gap energy of around 1.5eV and large absorption coefficient of over 10<SUP>4</SUP> cm<SUP>−1</SUP>. All the constituents of this material are abundant in the earth’s crust, and they are not toxic making it a smarter choice. Since 1996, after the initial success of the CZTS based solar cell (with its light to electrical conversion efficiency of 0.6%), significant progress in this research area has been achieved, especially in the last five years. Now-a-days, the conversion efficiency of the CZTS thin film solar cell has improved to 12%. Over 600 papers on CZTS have been published since 2001, and the majority of these discuss the preparation of CZTS thin films by different methods. So far, many physical and chemical techniques have been employed for preparing CZTS thin films. Among them, the pulsed laser deposition (PLD) is a versatile deposition method. PLD is a simple, but multipurpose, experimental method that finds use as a means of modeling a very diverse range of materials, and in extensive areas of thin film deposition and multi-layer research. This technique is suitable for depositing high quality films with complex compositions because of its influencing properties such as harmonious transfer of species from the target to substrate, enrichment in crystallinity, clean deposition, and simplicity and flexibility in the engineering design. On the occasion of the 25th anniversary of PLD, this manuscript, reviews the synthesis of CZTS semiconductor thin films fabricated by PLD. This review begins with a description of the PLD system, and then introduces the CZTS and preparation of the CZTS target for PLD deposition. A survey of pulsed laser deposited CZTS thin films and their solar cell performance is discussed in detail. Finally, we present perspectives for further developments of PLD for a CZTS based solar cell absorber layer.</P>

Non-vacuum mechanochemical route to the synthesis of Cu₂SnS₃ nano-ink for solar cell applications

Vanalakar, S.A.,Agawane, G.L.,Shin, S.W.,Yang, H.S.,Patil, P.S.,Kim, J.Y.,Kim, J.H. Elsevier 2015 Acta materialia Vol.85 No.-

<P><B>Abstract</B></P> <P>Cu-based ternary chalcogenides such as Cu<SUB>2</SUB>SnS<SUB>3</SUB> (CTS) are attracting increasing interest due to their outstanding opto-electronic properties. Herein, a simple, cost-effective non-vacuum mechanochemical synthetic route for preparing CTS nanocrystals with controlled size and composition is presented. CTS nanocrystalline powders were synthesized by ball milling and subsequent annealing in an H<SUB>2</SUB>S atmosphere. These nanocrystal samples were characterized using powder X-ray diffraction (P-XRD), Raman spectroscopy, ultraviolet–visible optical spectroscopy, energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) techniques. Texture structures with cubic crystallinity were observed from the P-XRD of (112), (200) planes of CTS nanopowders. The EDS results confirmed that the synthesized powders had an appropriate chemical purity. According to TEM/FE-SEM observations, a nanostructure CTS was obtained after 36h of mechanochemical processing followed by annealing. The average particle size of single phase CTS after 48h of milling was ∼45nm. Based on obtained data using characterization methods, reaction mechanism steps were proposed to clarify the reactions that occurred during the mechanochemical process. In order to prepare nanocrystal ink, ethanol was used as a solvent, and polyvinylpyrrolidone, which acts as an organic stabilizing agent, was added to the CTS powder to prepare a printable paste.</P>

Triton-X mediated interconnected nanowalls network of cadmium sulfide thin films via chemical bath deposition and their photoelectrochemical performance

Vanalakar, S.A.,Mali, S.S.,Jo, E.A.,Kim, J.Y.,Kim, J.H.,Patil, P.S. Elsevier 2014 SOLID STATE SCIENCES Vol.36 No.-

Thin films of cadmium sulfide (CdS) have been wet chemically deposited onto fluorine-doped tin oxide (FTO) coated conducting glass substrates by using non-ionic surfactant; Triton-X 100. An aqueous solution contains cadmium sulphate as a cadmium and thiourea as sulphur precursor. Ammonia used as a complexing agent. The results of measurements of the x-ray diffraction, Raman spectroscopy, optical spectroscopy, energy dispersive spectroscopy, scanning electron microscopy, Brunauer Emmett Teller (BET) surface areas and atomic force microscopy were used for the characterization of the films. These results revealed that the films are polycrystalline, consisting of CdS cubic phase. The films show a direct band gap with energy 2.39 eV. The films show interconnected nanowalls like morphology with well-defined surface area. Finally, the photoelectrochemical (PEC) performance of Triton-X mediated CdS thin film samples were studied. The sample shows photoelectrochemical (PEC) performance with maximum short circuit current density (J<SUB>sc</SUB>) 1.71 mA/cm<SUP>2</SUP> for larger area (1 cm<SUP>2</SUP>) solar cells.

Simplistic surface active agents mediated morphological tweaking of CdS thin films for photoelectrochemical solar cell performance

S.A. Vanalakar,M.P. Suryawanshi,S.S. Mali,A.V. Moholkar,J.Y.Kim,P.S. Patil,김진혁 한국물리학회 2014 Current Applied Physics Vol.14 No.12

This study reports on the formation of cadmium sulfide (CdS) nanostructures with controlled morphology synthesized via a simple chemical route in surface active agent environment. The effect of organic surface active agents (surfactants) as sodium dodecyl sulfate (SDS), polyethylene glycol (PEG) and cetyltrimethylammonium bromide (CTAB) on structural, morphological, optical and photoelectrochemical properties of CdS thin films have been studied. Our results reveal that the organic surfactants play key roles in tweaking the surface morphology. A compact spongy ball like morphology was observed for the CdS samples grown without organic surfactants. The cauliflower's with nanopetals from the CTAB, whereas crowded star fish like morphology is observed in PEG-mediated growth. Water hyacinth like morphology is tweaked using SDS. Considering the importance of these nanostructures, the growth mechanism has been discussed in details. Additionally, the samples are photoelectrochemically (PEC) active and having a compact surface with a nanoporous structure twig helps in improved photoelectrochemical performance compared to that of CdS deposits from surfactant free solution. This is a simplistic way to tune the morphology using surfactants, which can be applied to other energy conversion applications.

Simplistic surface active agents mediated morphological tweaking of CdS thin films for photoelectrochemical solar cell performance

Vanalakar, S.A.,Suryawanshi, M.P.,Mali, S.S.,Moholkar, A.V.,Kim, J.Y.,Patil, P.S.,Kim, J.H. Elsevier 2014 Current Applied Physics Vol.14 No.12

This study reports on the formation of cadmium sulfide (CdS) nanostructures with controlled morphology synthesized via a simple chemical route in surface active agent environment. The effect of organic surface active agents (surfactants) as sodium dodecyl sulfate (SDS), polyethylene glycol (PEG) and cetyltrimethylammonium bromide (CTAB) on structural, morphological, optical and photoelectrochemical properties of CdS thin films have been studied. Our results reveal that the organic surfactants play key roles in tweaking the surface morphology. A compact spongy ball like morphology was observed for the CdS samples grown without organic surfactants. The cauliflower's with nanopetals from the CTAB, whereas crowded star fish like morphology is observed in PEG-mediated growth. Water hyacinth like morphology is tweaked using SDS. Considering the importance of these nanostructures, the growth mechanism has been discussed in details. Additionally, the samples are photoelectrochemically (PEC) active and having a compact surface with a nanoporous structure twig helps in improved photoelectrochemical performance compared to that of CdS deposits from surfactant free solution. This is a simplistic way to tune the morphology using surfactants, which can be applied to other energy conversion applications.

Single-step hydrothermally grown nanosheet-assembled tungsten oxide thin films for sensitive and selective NO2 gas detection

Harale, N. S.,Dalavi, D. S.,Mali, Sawanta S.,Tarwal, N. L.,Vanalakar, S. A.,Rao, V. K.,Hong, Chang Kook,Kim, J. H.,Patil, P. S. Springer-Verlag 2018 JOURNAL OF MATERIALS SCIENCE - Vol.53 No.8

<P>A well-organized tungsten oxide (WO3) nanosheet-assembled microbricks have been synthesized by the hydrothermal route at 180 A degrees C with the help of peroxy-tungstic acid sol. The as-synthesized thin films have been characterized for structural, morphological and compositional studies by using X-ray diffraction, scanning electron microscopy and FT-Raman spectroscopy. The deposited WO3 thin films have been found to be polycrystalline in nature with the monoclinic crystal structure. The SEM micrographs revealed the formation of microbrick-like structure which was made up of two-dimensional (2D) nanosheets. The 2D nanosheets act as a nanobuilding blocks for the formation of microbricks. The gas-sensing performance of WO3 thin films was carried out for different gases, and it is observed that sensor exhibited maximum gas response towards Nitrogen dioxide (NO2) gas which is seven times higher than that of other gases at an operating temperature of 300 A degrees C over the concentration range of 5-100 ppm. WO3 microbricks sensor showed higher response about 11.5 and fast response-recovery characteristics towards NO2 gas, especially a much quicker gas response time of 16 s and recovery time of 260 s at 100 ppm.</P>

Rapid synthesis of CdS nanowire mesh <i>via</i> a simplistic wet chemical route and its NO₂ gas sensing properties

Vanalakar, Sharadrao A.,Patil, Vithoba L.,Patil, Pramod S.,Kim, Jin H. The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.6

<P>In this report, 1-D interconnected CdS nanowires were prepared rapidly <I>via</I> a wet chemical route at relatively low temperature, using cadmium sulphate, thiourea and ammonia as raw materials. The formation of a CdS nanowire mesh (CdS NW mesh) and its structural, optical, surface morphological properties and elemental composition were studied by various characterization techniques. The cubic crystal structure of the CdS interconnected nanowire mesh was confirmed <I>via</I> X-ray diffraction and field emission scanning electron microscopy analysis. The photoluminescence spectroscopy measurements reveal the presence of defects in the as synthesized CdS NW mesh. However, the defect states are beneficial for the gas sensing behavior. Therefore, the gas sensing properties of the CdS NW mesh were studied using NO2 as an analyte gas at moderate operating temperature. The nanowire mesh and inter-wire space were observed to play a crucial role in determining the gas sensing performance of the devices. The as synthesized CdS NW mesh shows a gas response of about 1850% to 100 ppm NO2 gas. In particular, our CdS based gas sensor showed a fifty fold better gas response towards NO2 gas than the earlier reports in the literature. Due to the high value of gas sensitivity, the reported CdS NW mesh could be a suitable candidate for NO2 sensing.</P>

Sensitive and selective NO₂ gas sensor based on WO₃ nanoplates

Shendage, S.S.,Patil, V.L.,Vanalakar, S.A.,Patil, S.P.,Harale, N.S.,Bhosale, J.L.,Kim, J.H.,Patil, P.S. Elsevier Sequoia 2017 Sensors and actuators. B, Chemical Vol.240 No.-

Gas sensors based on a chemiresistive metal oxide semiconductor are widely used including nitrogen dioxide (NO<SUB>2</SUB>) at a moderate temperature. In this work efforts are taken to fabricate NO<SUB>2</SUB> gas sensor using thin films of tungsten oxide (WO<SUB>3</SUB>) grown directly on to a soda-lime glass substrate without assistance of any seed layer by a simple and a facile hydrothermal technique. As per our knowledge, the deposition of nanostructured WO<SUB>3</SUB> thin films without assistance of any seed layer on the glass substrate was rarely reported. The WO<SUB>3</SUB> thin film samples were synthesized at various deposition times ranging from 3h to 7h and were characterized by X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy and Brunauer-Emmett-Teller techniques. The surface morphological and structural characterization showed the two dimensional (2D) nanoplate-like structure of as synthesized WO<SUB>3</SUB> thin films with plate thickness ranging from 90 to 150nm and had an orthorhombic structure, respectively. Moreover, the 2D nanoplates of WO<SUB>3</SUB> exhibited a gas response ~10 for 5ppm for toxic NO<SUB>2</SUB> gas at relatively low operating temperature. The new synthesis route and sensing behavior of as synthesized WO<SUB>3</SUB> nanoplates revealed a promising candidate for the fabrication of the cost effective gas sensors.

Compact nanoarchitectures of lead selenide via successive ionic layer adsorption and reaction towards optoelectronic devices

Bhat, T. S.,Vanalakar, S. A.,Devan, R. S.,Mali, S. S.,Pawar, S. A.,Ma, Y. R.,Hong, C. K.,Kim, J. H.,Patil, P. S. Springer Science + Business Media 2016 Journal of materials science Materials in electron Vol.27 No.5

<P>Thin films of Lead Selenide (PbSe) having compact nanoarchitectures were synthesized by a facile and cost-efficient successive ionic layer adsorption and reaction (SILAR) technique. The structural, morphological, optical and compositional properties were studied using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), UV-vis spectrophotometer, and X-ray photoelectron spectroscopy (XPS) techniques. Moreover, the effect of SILAR cycles on the morphology of PbSe thin films was investigated. XRD patterns revealed the formation of crystalline PbSe with the cubic crystal structure. FESEM images show shape evolution from nanoparticulate to merged pyramidal-like structure with variation in size from similar to 200 to 430 nm. The optical direct band gap energy of PbSe were varies from 1.32 to 1.20 eV with the increase in deposition cycles. The HRTEM and SAED results show the crystalline nature of the sample which is in good agreement with the XRD. The electrical characterizations were performed in order to obtain the ohmic behavior in the metal-semiconductor interface. The deposited thin films show a good ohmic behavior.</P>