Dipak V. Shinde

Layer-by-layer deposition and photovoltaic property of Ru-based metal–organic frameworks

In the present work, thin films of ruthenium based metal–organic frameworks are synthesized using a layer-by-layer (LbL) technique and the film is characterized using XRD, FE-SEM, UV/visible spectroscopy, cyclic voltammetry and photoluminance spectroscopy. Further, the feasibility of the MOF film as a sensitizer in a solar cell is investigated. The HOMO–LUMO level of the frameworks is estimated and is found to be suitable to allow the use of the frameworks as a sensitizer for TiO2. When TiO2 mesoporous film is sensitized with the LBL thin film of the frameworks and a Gratzel type liquid junction solar cell is constructed, it demonstrates the cell performance of Isc = 2.56 mA cm−2, Voc = 0.63 V, FF = 0.63, and Eff = 1.22%. Photoluminescence spectroscopy and electrochemical impedance spectroscopy show that iodine doping into the frameworks is essential to facilitate the photogenerated electron transfer from the frameworks to TiO2.

An ion exchange mediated shape-preserving strategy for constructing 1-D arrays of porous CoS1.0365 nanorods for electrocatalytic reduction of triiodide

Based on a coordination chemistry approach, the present work reports on the synthesis of thin films of various cobalt hydroxycarbonate nanostructures such as nanobeams, nanoneedles, and bending nanorods using three different cobalt precursors viz. Cl−, NO3− and CH3COO−. After pyrolysis in air, the hydroxycarbonate nanostructures are transferred into 1-D arrays of Co3O4 nanorods. The obtained 1-D Co3O4 nanostructures are then transformed into the corresponding analogous shaped 1-D arrays of porous cobalt sulfide (CoS1.0365) nanostructures using a wet chemical transformation method based on an ion exchange approach. The nanostructured films before and after the ion exchange reaction are characterized using field emission electron scanning microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), and inductively coupled plasma mass spectroscopy (ICP-MS) measurements. As a proof-of-concept demonstration for the application, various shaped CoS1.0365 nanorod films synthesized are investigated as a Pt-free counter electrode in dye-sensitized-solar cells (DSSCs). The influence of three different counter anions of the cobalt precursors on the structural, textural, and morphological aspects, and thereby their influence on electronic and electrochemical properties, has been investigated. A correlation among electrical conductivity, charge transfer resistance and electrocatalytic performance of various CoS1.0365 nanorod films obtained from different cobalt precursors has been established. Among the various nanostructures, the thicker nanorod film synthesized using a chloride precursor has demonstrated the best electrocatalytic behavior toward triiodide reduction, which led to a short circuit current density of 18.04 mA cm−2 and energy conversion efficiency of 7.4% of the DSSC. This photovoltaic performance is highly competitive to a current density of 18.26 mA cm−2 and energy conversion efficiency of 7.7% exhibited by the standard Pt counter electrode.

A coordination chemistry approach for shape controlled synthesis of indium oxide nanostructures and their photoelectrochemical properties

Indium oxide (In2O3) is an important wide band-gap semiconductor having applications in a variety of optoelectronic devices. We report here on the low temperature solution deposition of In(OH)3 and In(SO4)(OH)·H2O architectures with various shapes such as cubes, maize corns and giant crystals. The In2O3 nanostructures are then obtained by solid state transformation of In(OH)3 and In(SO4)(OH)·H2O architectures. Shape control is achieved by controlling the local concentration of In3+ ions available for reaction by applying the principles of coordination chemistry, thereby obviating the need of any shape controlling agents. The phase and surface composition is obtained by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. The XPS is used to probe the defect structure of In2O3 architecture. Optical properties of the films, studied by UV-Vis absorption and photoluminescence (PL) spectroscopy measurements, show that the different morphologies have different band-gaps. Furthermore current–voltage characteristics of In2O3–CdSe photoelectrochemical cells are studied, which show that cube–CdSe samples display excellent photovoltaic behaviour, exhibiting a short circuit current density in excess of 10 mA cm−2. The charge transport properties of the In2O3–CdSe photoanodes are studied by impedance spectroscopy, which shows that cube–CdSe samples have lowest resistance to charge transfer.

CdS buffer-layer free highly efficient ZnO-CdSe photoelectrochemical cells

Highly reproducible, wet-chemically processed, CdS buffer-layer free ZnO-CdSe photoelectrochemical cells with 3.38% power conversion efficiency have been fabricated. An enhanced current density is observed due to increase in number of injected photoelectrons with CdSe nanoparticles loading time. Impedance spectroscopy results suggest that interfacial resistance is strongly dependant on CdSe nanoparticles loading time.

SnO2 nanowall-arrays coated with rutile-TiO2 nanoneedles for high performance dye-sensitized solar cells

A novel architecture of SnO(2) nanowall-arrays coated with rutile-TiO(2) nanoneedles is fabricated for the first time and envisaged in dye-sensitized solar cells. Devices constructed using these architectures showed a power conversion efficiency of 4.12%, which is the highest among the SnO(2) nanostructures grown on conducting substrates by wet chemical methods.

Anodically fabricated self-organized nanoporous tin oxide film as a supercapacitor electrode material

Self-organized nanoporous tin oxide films were fabricated by anodizing a tin substrate in an aqueous electrolyte containing oxalic or phosphoric acid. The films were characterized using FE-SEM, XRD, XPS, and TGA. In addition, the supercapacitive properties of the porous oxide films were measured using cyclic voltammetry and galvanostatic charge/discharge technique. The film demonstrated a maximum specific capacitance of 274 F g−1 with long life in electrochemical charge/discharge cycles.

Thickness of the hole transport layer in perovskite solar cells: performance versus reproducibility

We studied the effect of the hole transport layer (HTL) thickness on photovoltaic properties of meso-superstructured perovskite solar cells based on CH3NH3PbI3−xClx. We found that there is an interplay between photovoltaic performance and reproducibility: thinning the HTL increased performances of the devices but reduced their reproducibility.

Synthesis and enhancement of photocatalytic activities of ZnO by silver nanoparticles

Herein, we reports synthesis, characterization and photocatalytic degradation of Rhodamine B under natural sunlight using zinc oxide and Ag-ZnO composite. Zinc oxide nanoparticles were prepared by simple wet chemical method using ethanol-water mixture. Ag-ZnO composite was prepared in two steps by dispersing synthesized ZnO in silver nitrate solution and subsequently reducing it with Ocimum tenuiflorum leaves extract as bioreducing agent. The synthesized bare zinc oxide and Ag-ZnO composite was characterized by various techniques like XRD, DRS, FE-SEM, TEM, SAED, PSD, Zeta potentials, etc. Zinc oxide being wide band gap material can absorbs UV light from solar spectrum which is only 5% so is not efficient material for dye degradation under sunlight. The absorption of visible light was increased by preparing the Ag-ZnO composite. The enhancement in photocatalytic activities of Ag-ZnO composite was observed than bare ZnO. This enhancement is due to shift of absorption edge of ZnO in visible region and decrease in band gap.

Improved Photoelectrochemical Cell Performance of Tin Oxide with Functionalized Multiwalled Carbon Nanotubes-Cadmium Selenide Sensitizer.

Here we report functionalized multiwalled carbon nanotubes (f-MWCNTs)-CdSe nanocrystals (NCs) as photosensitizer in photoelectrochemical cells, where f-MWCNTs were uniformly coated with CdSe NCs onto SnO2 upright standing nanosheets by using a simple electrodeposition method. The resultant blended photoanodes demonstrate extraordinary electrochemical properties including higher Stern-Volmer constant, higher absorbance, and positive quenching, etc., caused by more accessibility of CdSe NCs compared with pristine SnO2-CdSe photoanode. Atomic and weight percent changes of carbon with f-MWCNTs blending concentrations were confirmed from the energy dispersive X-ray analysis. The morphology images show a uniform coverage of CdSe NCs over f-MWCNTs forming a core-shell type structure as a blend. Compared to pristine CdSe, photoanode with f-MWCNTs demonstrated a 257% increase in overall power conversion efficiency. Obtained results were corroborated by the electrochemical impedance analysis. Higher scattering, more accessibility, and hierarchical structure of SnO2-f-MWCNTs-blend-CdSe NCs photoanode is responsible for higher (a) electron mobility (6.89 × 10(-4) to 10.89 × 10(-4) cm(2) V(-1) S(1-)), (b) diffusion length (27 × 10(-6)),

A simple, room temperature, solid-state synthesis route for metal oxide nanostructures

In this work, we demonstrate an extremely simple but highly effective strategy for the synthesis of various functional metal oxides (MOs) such as ZnO, In2O3, Bi2O3, and SnO2 nanoparticles with various distinct shapes at room temperature via a solid-state reaction method. The method involves only mixing and stirring of the corresponding metal salt and NaOH together in the solid phase, which yields highly crystalline metal oxides within 5–10 min of reaction time. The obtained paste can be directly doctor-bladed onto a variety of substrates for photoelectrochemical applications. The crystal structure and surface composition of the MOs are obtained by X-ray diffraction patterns, energy dispersive analysis and X-ray photoelectron spectroscopy, respectively. The surface morphology is confirmed from the scanning electron microscopy surface photo-images. The surface area and pore size distribution are studied by the N2 adsorption method. As a proof-of-concept demonstration for the application, ZnO nanoplate structures are envisaged in DSSCs as photoanodes, which enables us to obtain excellent photovoltaic properties with a power conversion efficiency of 5%. The proposed method does not require a sophisticated instrumental setup or harsh conditions, and the method is easily scalable. Hence, it can be applied for the cost-effective and large-scale production of MO nanoparticles with high crystallinity.