Panikar Sathyaseelan Archana

High performance dye-sensitized solar cells with record open circuit voltage using tin oxide nanoflowers developed by electrospinning

Flower shaped nanostructures of an architypical transparent conducting oxide, SnO2, have been synthesized by an electrospinning technique for the first time by precisely controlling the precursor concentration in a polymeric solution. The flowers were made up of nanofibrils of diameter ∼70–100 nm, which in turn consisted of linear arrays of single crystalline nanoparticles of size 20–30 nm. Mott–Schottkey analysis shows that flowers have an order of magnitude higher electron density compared with the fibers despite their chemical similarity. Dye-sensitized solar cells fabricated using the flowers showed a record open circuit voltage of ∼700 mV and have one of the highest photoconversion efficiencies so far achieved with SnO2 and the iodide/triiodide electrolyte. The photoaction spectra and impedance spectroscopic measurements show that the flowers are characterized by a higher electron lifetime, owing to their enhanced crystallinity, compared to the conventional fibrous structure.

NanoCOT: Low-Cost Nanostructured Electrode Containing Carbon, Oxygen, and Titanium for Efficient Oxygen Evolution Reaction.

Developing high-efficiency, durable, and low-cost catalysts based on earth-abundant elements for the oxygen evolution reaction (OER) is essential for renewable energy conversion and energy storage devices. In this study, we report a highly active nanostructured electrode, NanoCOT, which contains carbon, oxygen, and titanium, for efficient OER in alkaline solution. The NanoCOT electrode is synthesized from carbon transformation of TiO2 in an atmosphere of methane, hydrogen, and nitrogen at a high temperature. The NanoCOT exhibits enhanced OER catalytic activity in alkaline solution, providing a current density of 1.33 mA/cm(2) at an overpotential of 0.42 V. This OER current density of a NanoCOT electrode is about 4 times higher than an oxidized Ir electrode and 15 times higher than a Pt electrode because of its nanostructured high surface area and favorable OER kinetics. The enhanced catalytic activity of NanoCOT is attributed to the presence of a continuous energy band of the titanium oxide electrode with predominantly reduced defect states of Ti (e.g., Ti(1+), Ti(2+), and Ti(3+)) formed by chemical reduction with hydrogen and carbon. The OER performance of NanoCOT can also be further enhanced by decreasing its overpotential by 150 mV at a current density of 1.0 mA/cm(2) after coating its surface electrophoretically with 2.0 nm IrOx nanoparticles.

Near band-edge electron diffusion in electrospun Nb-doped anatase TiO2 nanofibers probed by electrochemical impedance spectroscopy

Charge transport through Nb-doped anatase TiO2 nanofibers (diameter ∼100 nm) developed by electrospinning is studied under the framework of hopping transport using electrochemical impedance spectroscopy measurements. It is observed that the Fermi level of TiO2 rise close to its conduction band and result in a band-edge type diffusion mechanism even at low bias voltages when 2 at % Nb atoms replaces the Ti atoms in the anatase lattice. The Nb-doped anatase electrospun nanofibers showed high chemical capacitance, high effective diffusion coefficient, and lower transport resistance compared to the undoped samples and conventional nanoparticles (25 nm).

Functional films of polymer-nanocomposites by electrospinning for advanced electronics, clean energy conversion, and storage

An approach for making functional films of polymer – nanocomposites under the framework of nanotechnology is presented. In this methodology, nanowires of an inorganic functional material are dispersed in a functional polymeric medium and the resultant solution is developed into solid films by electrospinning technique. The final structure is a nanofibrous film – each nanofiber contains a percolating network of inorganic nanowires. The nanowires reduce the percolation threshold compared to those nanoparticles and maintain the flexibility and/or light weight of the polymers and nanomaterials. This methodology has been tested for a number of material architectures for electronic and energy devices.

Electrospun TiO 2 nanorods assembly sensitized by mercaptosuccinic acid-capped CdS quantum dots for solar cells: Subtitle as needed (paper subtitle)

CdS quantum dots (QDs) capped with mercaptosuccinic acid (MSA) as the surface passivating ligand were anchored to electrospun TiO2 nanorod surfaces using the terminal carboxylic acid groups present on MSA. The as-synthesized materials and the dye-sensitized solar cells were characterized by spectroscopy, microscopy and photocurrent measurements, respectively. Best solar cells fabricated by the method showed an efficiency of 0.07%. We believe that the simple, one-pot fabrication of the QDs and their assembly into solar cells are significant steps in QD-sensitized solar cell research.