Showing papers by "Kothandaraman Ramanujam published in 2021"

Electrode and Conductive Additive Compatibility Yielding Excellent Rate Capability and Long Cycle Life for Sustainable Organic Aqueous Zn-Ion Batteries

Abstract: Aqueous Zn-ion batteries have tremendous potential to penetrate the energy storage market, as an alternative to Li-ion batteries, given the high volumetric capacity of Zn (5853 mAh cm–3), cost-effe...

Molecular engineering of near-infrared active boron dipyrromethene moiety with various donors and acceptors for tuning the absorption behavior and electron injection of the resultant dyes

Abstract: Small molecules having an absorption band beyond 750 nm for DSSC applications are scarce in the literature. Derivatives of boron dipyrromethane (BODIPY) are popular fluorophores in life sciences and hence used in fluorescent microscopy for staining different intracellular organelles, and BODIPY-based dye molecules have been known for the strong absorption in the visible and near IR regions. A series of twelve (Donor-π-linker)2-Ancillary Acceptor-Acceptor ((D-π)2-An-A)) based metal-free organic dyes comprising BODIPY moiety as an ancillary acceptor (An) were designed to fine-tune the panchromatic behavior of BODIPY dyes. Based on the density-functional theory (DFT) and time-dependent DFT, the photophysical and photoelectrochemical properties of the dyes were investigated. To convey the objective of the work, several photovoltaic parameters, such as dye regeneration driving force (ΔGreg), reorganization energy (Λ), chemical reactivity parameters, dye adsorption energy ( E a d s ), and the density of states were calculated to justify the suitability of the dyes for the DSSCs application. This study identified six dyes with carbazole and phenothiazine-based donors as DSSC suitable panchromatic dyes.

Characteristics of an Indigenously Developed 1 KW Vanadium Redox Flow Battery Stack

Abstract: Efficient and high-power electrical energy storage is a key technology to harness renewable sources of energy. Vanadium redox flow battery (VRFB) systems have emerged as strong contenders for large-scale energy storage applications. The paper presents the characteristics of an indigenously developed 1 kW VRFB stack of two designs. The fabrication of stack was preceded by a large amount of cell-level studies; important characteristics of interest to a design engineer such as materials of construction, cell sizes, operating conditions, power, charge/discharge capacity, energy efficiency and cycling behaviour are reported here. The project aims to develop eventually a 5 kW/25 kWh redox flow battery system capable of drawing electrical power from solar PV panels or the main grid, as necessary, and deliver uninterrupted power to a community of mixed DC/AC users.

Computational study of 4,4′-dimethoxy triphenylamine donor linked with low band gap π-spacers by single and double bonds for DSSC applications

Abstract: In this work, ten metal-free organic dyes based on the 4,4′-dimethoxy triphenylamine donor and cyanoacrylic acid acceptor were designed and computationally studied for their potential in DSSC. The different π-spacers employed for the comparative study are benzothiadiazole (TC1), quinoxaline (TC2), benzotriazole (TC3), phenathrothiadiazole (TC4) and dihexylcyclopentadithiophene (TC5). The 4,4′-dimethoxy triphenylamine donor was paired with the π-spacers via single-bond/double-bond joints. This computational work mainly aims at determining the impact of the π-spacer on the geometrical and optoelectronic properties using the Density Functional Theory (DFT) and Time-Dependent-DFT approaches. Our studies revealed that all of the designed dyes have strong absorptions in the range of 560–700 nm with satisfactory oscillator strengths and light-harvesting efficiencies (LHE). Several other photovoltaic parameters, such as absorption maximum, driving force for dye regeneration (Greg), energy level alignment, chemical reactivity parameters, reorganization energy, and dye adsorption energy (Eads), were measured to determine the role of heterocyclic π-spacers in improving the efficiency of a solar cell. Based on the above parameters, the dye with benzothiadiazole spacer was identified to be the most promising candidate among those studied. These findings provide valuable hints for the fast screening of π-spacers for the efficient molecular engineering of organic sensitizers.

A computational approach on engineering short spacer for carbazole-based dyes for dye-sensitized solar cells

Abstract: Donor-π-linker-acceptor (D-π-A) push–pull dye molecules are most common in dye-sensitized solar cells (DSSCs) applications. Selection of dye molecules for DSSCs is based on their ability to absorb light in the visible spectrum. This can be done more efficiently by positioning the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) with respect to the conduction band of the semiconductor and the redox potential of the electrolyte, respectively. The photocurrent is manipulated by the extent of light absorption, planarity of the π-linker for efficient intramolecular charge transfer (ICT), oxidized dye reorganization energy (Λ) and dye regeneration driving force (ΔGreg). In a quest of achieving panchromatic absorption up to near-IR region, mostly electron-rich chromophores and their oligo form were used in the π-segment, but this approach led to poor ICT. In this computational analysis, we have explored the effect of electron-withdrawing (cyano (–CN)) and donating groups (methoxy (-OMe)) in three different π-segment length to understand the carbazole dyes’ suitability for DSSCs using onset wavelength (λonset), Λ, ICT and ΔGreg as the figure-of-merits.