Surface induced charge transfer in Cu_xIn_2-xS₃ nanostructures and their enhanced photoelectronic and photocatalytic performance

Ilanchezhiyan, P.,Mohan Kumar, G.,Xiao, Fu,Siva, C.,Yuldashev, Shavkat U.,Lee, D.J.,Jeon, H.C.,Kang, T.W. Elsevier 2019 Solar energy materials and solar cells Vol.191 No.-

<P><B>Abstract</B></P> <P>Multi-functional semiconducting nanostructures are gaining popularity for application in photoelectronics, energy storage devices and also in industrial and environmental remediation functions. In this regard, Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> nanostructures were investigated in detail for their photoelectrical and photocatalytic performance. Their physico-chemical characteristics were at first studied using X-ray diffraction, Raman, UV–vis absorbance, X-ray photoelectron spectroscopy and high resolution electron microscopic tools. Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> based flip chip Schottky diodes were demonstrated to attest their improved conductivity and enhanced photoelectrical performance. The photo switching capabilities of a type II <I>p-n</I> CdTe/Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> heterojunction was also investigated. In both the device configurations, the current-voltage (I-V) characteristics revealed the forward current and rectification ratio to improve under lower threshold voltages. The time-dependent photoresponse characteristics affirmed the stability of diodes, augmenting the improved/effective separation of photo generated electron hole pairs under illumination. Additionally, the photocatalytic performances of Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> nanostructures were inferred under visible light conditions through effective remediation of methylene blue (MB) dye molecules. The obtained results infer the Cu interaction in tetragonal lattice of Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> to promote the surface induced charge transfer mechanism in respective nanostructures, thereby enhancing their photoelectronic and photocatalytic functionalities.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> multi-functional nanostructures were fabricated by hydrothermal route. </LI> <LI> Cu interaction in tetragonal lattice of Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> promotes surface induced charge transfer. </LI> <LI> Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> diodes demonstrate improved conductivity/photoelectrical performance. </LI> <LI> Reproducible photo switching was studied along <I>p-n</I> CdTe/Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> heterojunction. </LI> <LI> Cu<SUB>x</SUB>In<SUB>2-x</SUB>S<SUB>3</SUB> nanostructures exhibit excellent photocatalytic performance under visible light. </LI> </UL> </P>

Interfacial charge transfer in ZnTe/ZnO nano arrayed heterostructures and their improved photoelectronic properties

Ilanchezhiyan, P.,Mohan Kumar, G.,Xiao, Fu,Madhankumar, A.,Siva, C.,Yuldashev, Shavkat U.,Cho, H.D.,Kang, T.W. North-Holland 2018 Solar Energy Materials and Solar Cells Vol. No.

<P><B>Abstract</B></P> <P>The demand for low-cost high efficient photoelectronic devices tends to drive the present need for investigations on advanced multi-functional semiconducting nanostructures. In this regard, the physico-chemical traits of sonochemically processed ZnTe nanostructures and hydrothermally grown ZnO nanostructures were studied using Raman, UV–vis absorbance, X-ray photoelectron spectroscopy and high resolution microscopic tools. The p-n ZnTe/ZnO heterojunctions were then fabricated via spin casting a colloidal ZnTe suspension on periodically aligned ZnO nanowires and investigated for their photoelectronic functionalities. The current-voltage (I-V) characteristics revealed an obvious rectifying behaviour with the forward current and rectification ratio getting improved on lowering the threshold voltages. The series resistance of the diodes were additionally studied using the dV/dlnI derivate plots. The stability of the diodes were also affirmed using their time-dependent photoresponse characteristics, which actually suggested the improved and effective separation of photo generated electron hole pairs across the interface. Finally, the ZnTe/ZnO heterojunction behaviour was assimilated using the electrochemical impedance spectroscopic (EIS) results that were studied individually for ZnTe and ZnO nanostructures and collectively across ZnTe/ZnO heterostructure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ZnTe integrated ZnO nanowire diodes revealed excellent rectifying behaviour/rectification ratio. </LI> <LI> Series resistance of diodes were studied using dV/dlnI derivate plots. </LI> <LI> Stability of devices were evidenced through their photoresponse characteristics. </LI> <LI> Electrochemical data revealed improved interfacial charge transfer along the heterostructure. </LI> </UL> </P>

A structural property study on the role of Sm ions in nano-textured Zn(1−x)Sm x O thin films for green emission

Ilanchezhiyan, P.,Mohan Kumar, G.,Suresh, S.,Kang, Tae Won,Jayavel, R. Springer-Verlag 2013 Journal of materials science. Materials in electro Vol.24 No.8

Ultrasonic-assisted synthesis of ZnTe nanostructures and their structural, electrochemical and photoelectrical properties

Ilanchezhiyan, P.,Mohan Kumar, G.,Xiao, Fu,Poongothai, S.,Madhan Kumar, A.,Siva, C.,Yuldashev, Sh.U.,Lee, D.J.,Kwon, Y.H.,Kang, T.W. Elsevier 2017 Ultrasonics sonochemistry Vol.39 No.-

<P><B>Abstract</B></P> <P>Colloidal zinc telluride (ZnTe) nanostructures were successfully processed through a simple and facile ultrasonic (sonochemical) treatment for photoelectronic applications. The particle-like morphological features, phase and nature of valence state of various metal ions existing in ZnTe were examined using electron and X-ray photoelectron spectroscopic tools. Raman spectroscopic measurements revealed the dominance of exciton-phonon coupling and occurrence of TeO<SUB>2</SUB> traces in ZnTe through the corresponding vibrations. Optical bandgap of the ZnTe suspension was estimated to be around 2.15eV, authenticating the direct allowed transitions. The <I>p</I>-type electrical conductivity and charge carrier density of ZnTe were additionally estimated from the Bode, Nyquist and Mott-Schottky type impedance plots. The photoelectrical properties of ZnTe were investigated by fabricating <I>p</I>-ZnTe/<I>n</I>-Si heterostructures and studying their corresponding current-voltage characteristics under dark and white light illumination. The diodes revealed excellent rectifying behaviour with significant increase in reverse current under illumination. The stability of the devices were also affirmed through the time-dependent photoresponse characteristics, which actually suggested the improved and effective separation of photo generated electron hole pairs across the integrated heterojunctions. The obtained results also augment the potential of sonochemically processed ZnTe for application in photo detection and sensor related functions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanostructured ZnTe were ultrasonically processed for photoelectronics. </LI> <LI> Raman, XPS and electron microscopic tools affirmed their physico-chemical traits. </LI> <LI> Electrical properties were studied using Nyquist and Mott-Schottky plots. </LI> <LI> <I>I</I>-<I>V</I> studies augment the improved photo response in p-ZnTe/n-Si heterojunctions. </LI> </UL> </P>

Colloidal synthesis of Gd3+ doped ZrO2 based dielectrics and their structural and electrochemical property studies

Ilanchezhiyan, P.,Siva, C.,Kang, T. W.,Mohan Kumar, G. Springer Science + Business Media 2016 Journal of materials science Materials in electron Vol.27 No.6

<P>Solution processed wide band gap dielectrics have nowadays started to receive renewed interest for practical application in semiconductor electronics. In this regard, undoped and gadolinium (Gd) doped zirconia (ZrO2) nanocrystallites were colloidally processed and their potential for dielectric applications has been demonstrated. X-ray diffraction measurements revealed the effective crystallization of nanostructures and the successful substitution of Gd ions into the cubic ZrO2 matrix. The particulate-like characteristics of undoped and Gd doped ZrO2 nanostructures were examined through the electron microscopes, which hardly revealed any difference among them. The optical band gap of ZrO2 nanostructures was determined to be around 4.64-4.80 eV from the absorbance measurements. The potential of Gd doped ZrO2 nanostructures for dielectric functions were evaluated through electrochemical impedance spectroscopic measurements. The improved capacitance values estimated from the Nyquist plots suggests the potential of the investigated materials for low power and low voltage electronic applications.</P>

Photoswitching and photocatalytic functions of Sn_xCu_1−xS nanostructures

Ilanchezhiyan, P.,Kumar, G. Mohan,Siva, C.,Venkatasubbu, G. Devanand,Kang, T.W.,Kim, D.Y. Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.489 No.-

<P><B>Abstract</B></P> <P>Ultra-thin semiconducting nanostructures are garnering strategic importance in energy and environment remediation applications. In this regard, Sn<SUB>x</SUB>Cu<SUB>1−x</SUB>S nanostructures were processed through an eco-friendly chemical route and investigated in detail for photoswitching and photocatalytic functions. X-ray diffraction, FT-IR, Raman, UV–vis absorbance and high-resolution microscopic tools were initially used to examine the physico-chemical traits of Sn<SUB>x</SUB>Cu<SUB>1−x</SUB>S nanostructures. Ambiguous evidence for the substitution of Sn ions in place of Cu ions was attained through X-ray photoelectron spectroscopy. The photocatalytic performance of Sn<SUB>x</SUB>Cu<SUB>1−x</SUB>S systems was investigated through effective remediation of organic dye molecules under visible light. Scavenger based photocatalytic experiments were additionally carried out to infer the degradation mechanism. Type II <I>p-n</I> Sn<SUB>x</SUB>Cu<SUB>1−x</SUB>S/In<SUB>2</SUB>S<SUB>3</SUB> heterojunction diodes were also demonstrated for the first time with improved electrical conductivity and photoelectrical performances. The rectification ratio, forward current values and photo switching capabilities of these diodes were noted to improve in the Current vs. Voltage (I-V) and Current vs. Time (I-T) curves as a function of Sn composition and applied bias potential. The excellent photo switching stability augments the photo generated carriers to be effectively separated along the p-n junctions. The enhanced photoelectronic and photocatalytic functionalities in Sn<SUB>x</SUB>Cu<SUB>1−x</SUB>S has finally been reasoned to the improved charge transfer kinetics in the respective architectures, resulting from the effective Sn interaction in hexagonal host lattice.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sn<SUB>x</SUB>Cu<SUB>1−x</SUB>S nanostructures were fabricated by hydrothermal route. </LI> <LI> The nanostructures exhibited excellent photocatalytic activity under visible light. </LI> <LI> Sn interaction in hexagonal host lattice promoted their photocatalytic performance. </LI> <LI> p-Sn<SUB>x</SUB>Cu<SUB>1−x</SUB>S/n-In<SUB>2</SUB>S<SUB>3</SUB> diodes demonstrated improved photoswitching performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Tunable UV-visible absorption of SnS2layered quantum dots produced by liquid phase exfoliation

Fu, Xiao,Ilanchezhiyan, P.,Mohan Kumar, G.,Cho, Hak Dong,Zhang, Lei,Chan, A. Sattar,Lee, Dong J.,Panin, Gennady N.,Kang, Tae Won The Royal Society of Chemistry 2017 Nanoscale Vol.9 No.5

<P>4H-SnS2 layered crystals synthesized by a hydrothermal method were used to obtain via liquid phase exfoliation quantum dots (QDs), consisting of a single layer (SLQDs) or multiple layers (MLQDs). Systematic downshift of the peaks in the Raman spectra of crystals with a decrease in size was observed. The bandgap of layered QDs, estimated by UV-visible absorption spectroscopy and the tunneling current measurements using graphene probes, increases from 2.25 eV to 3.50 eV with decreasing size. 2-4 nm SLQDs, which are transparent in the visible region, show selective absorption and photosensitivity at wavelengths in the ultraviolet region of the spectrum while larger MLQDs (5-90 nm) exhibit a broad band absorption in the visible spectral region and the photoresponse under white light. The results show that the layered quantum dots obtained by liquid phase exfoliation exhibit wellcontrolled and regulated bandgap absorption in a wide tunable wavelength range. These novel layered quantum dots prepared using an inexpensive method of exfoliation and deposition from solution onto various substrates at room temperature can be used to create highly efficient visible-blind ultraviolet photodetectors and multiple bandgap solar cells.</P>

MWCNT/CdS nanobelt based hybrid structures and their enhanced photoelectrical performance

Lee, Dong Jin,Ilanchezhiyan, P.,Mohan Kumar, G.,Kwak, Dong Wook,Woo, Yong Deuk,Kim, Deuk Young,Kang, Tae Won Elsevier 2017 Chemical physics letters Vol.667 No.-

<P>In this work, we report on single CdS nanobelts (NB), Multi-walled carbon nanotube (MWCNT)/CdS NB and MWCNT: Cu/CdS NB based hybrid devices for photodetector applications. The electrical properties of the MWCNT: Cu/CdS NB devices tends to exhibit excellent photo to dark current ratio and a higher photoresponse of 7.5 times than that of pristine CdS device. The results also suggest MWCNT: Cu/CdS NB for potential application in photodetectors that require high photocurrent to dark current ratio and remarkable stability. (C) 2016 Elsevier B.V. All rights reserved.</P>

Electrical property studies on chemically processed polypyrolle/aluminum doped ZnO based hybrid heterostructures

Mohan Kumar, G.,Ilanchezhiyan, P.,Madhan Kumar, A.,Yuldashev, Sh.U.,Kang, T.W. Elsevier 2016 Chemical physics letters Vol.649 No.-

<P>A hybrid structure based on p-type polypyrolle (PPy) and n-type aluminum (Al) doped ZnO nanorods was successfully constructed. The effect of Al doping on material properties of wurtzite structured ZnO were studied using several analytical techniques. To establish the desired hybrid structure, pyrrole monomers were polymerized on hydrothermally grown Al doped ZnO nanorods by chemical polymerization. The current-voltage characteristics on the fabricated PPy/A1 doped ZnO heterostructures were found to exhibit excellent rectifying characteristics under dark and illumination conditions. The obtained results augment the prescribed architecture to be highly suitable for high-sensitivity optoelectronic applications. (C) 2016 Elsevier B.V. All rights reserved.</P>

Structural and magnetic property studies on low temperature chemically synthesised one-dimensional Zn1−xNixO nanorods

Mohan Kumar, G.,Ilanchezhiyan, P.,Poongothai, S.,Park, Jinsub,Jayavel, R. Springer-Verlag 2014 Journal of materials science Materials in electron Vol.25 No.3