Jolly Bhadra

A BHJ-thin-film/liquid-electrolyte based electrochemical-sensor for visible light-detection

The current study presents a new type of inexpensive and very sensitive bulk heterojunction (BHJ) organic photo-sensor (OPS) configuration that incorporates a layer of liquid electrolyte into the conventional BHJ photodiode arrangement. Initially, a P3HT:PCBM blend based photo-anode was deposited onto ITO substrates using spin coating. Then the semiconductor coated photo-anode was attached to a Pt/ITO counter electrode. A 40 µm gap between photo-anode and counter electrode was filled with a liquid (iodine based) HI-30 electrolyte. Various electrical parameters including ideality factor, series and shunt resistance were extracted from the current–voltage characteristics under dark and light conditions. The value of mobility measured under dark conditions was found to be 25.58 × 10−6 m2 V−1 s−1. In addition, the samples were found to have a series and shunt resistance of 133.33 Ω and 74.70 kΩ, respectively. Under illumination, the fabricated photodiodes exhibited a linear current–irradiance relationship, with a rapid response time, when exposed to transient light, thus making the newly proposed hybrid BHJ photo-diode configuration a potential alternative to the conventional photo-sensors.

Flexible thermo-electrochemical cells using Iodolyte HI-30 for conversion of low-grade heat to electrical energy

In this research work, we investigated the flexible thermo-electro chemical cells (TECs) for the conversion of low-grade heat into electrical energy in the temperature range of 20–70 °C. The TECs were fabricated using 30 mM iodide/tri-iodide (Iodolyte HI-30) in acetonitrile as a redox couple. A TEC consists of a carbon/Iodolyte HI-30/carbon structure. The cell contains a flexible polymer tube, filled with the electrolyte, whereas the openings of the tube have been sealed using carbon electrodes. Gradients of temperature (ΔT) up to 50 °C have been created. The Seebeck voltages and short-circuit currents (Isc) were found to be 8–17 mV and 100–425 μA, respectively, in the 20–70 °C temperature range. It was found that the TECs could provide sufficient power to drive low-power electronic devices and could be used for measurement of temperature gradients as well. Furthermore, this work identifies the directions for realizing flexible thermo-electric cells that can be potentially used for several applications in the medical segment where, besides electrical and mechanical stability, flexibility is paramount.

Polyaniline/Polystyrene Blends: In-Depth Analysis of the Effect of Sulfonic Acid Dopant Concentration on AC Conductivity Using Broadband Dielectric Spectroscopy

This work presents an in-depth analysis of the alternating current (AC) conductivity of polyaniline-polystyrene (PANI-PS) blends doped with camphor sulfonic acid (CSA) and prepared using an in situ dispersion polymerization technique. We prepared the blends using fixed ratios of PS to PANI while varying the concentration of the CSA dopant. The AC conductivity of the blends was investigated using broadband dielectric spectroscopy. Increasing CSA resulted in a decrease in the AC conductivity of the blends. This behaviour was explained in terms of the availability of a lone pair of electrons of the NH groups in the polyaniline, which are typically attacked by the electron-withdrawing sulfonic acid groups of CSA. The conductivity is discussed in terms of changes in the dielectric permittivity storage ( ), loss ( ), and modulus ( ) of the blends over a wide range of temperatures. This is linked to the glass transition temperature of the PANI. Dielectric spectra at low frequencies indicated the presence of pronounced Maxwell-Wagner-Sillars (MWS) interfacial polarization, especially in samples with a low concentration of CSA. Electrical conduction activation energies for the blends were also calculated using the temperature dependence of the direct current (DC) conductivity at a low frequency ( ), which exhibit an Arrhenius behaviour with respect to temperature. Scanning electron microscopy revealed a fibrous morphology for the pure PANI, while the blends showed agglomeration with increasing CSA concentrations.