Showing papers by "Kothandaraman Ramanujam published in 2020"
TL;DR: A series of (D-π)2-An-A based organic dyes containing a boron dipyrromethene (BODIPY) moiety as an ancillary acceptor (An) derivative were chosen, and the effect of donor moieties (diarylamine, carbazole, azepine, and dibenzazepine) was investigated to understand their photophysical and photoelectrochemical properties by employing density functional theory (DFT) and time-dependent DFT as mentioned in this paper.
Abstract: A series of (D-π)2–An–A based organic dyes containing a boron dipyrromethene (BODIPY) moiety as an ancillary acceptor (An) derivative were chosen, and the effect of donor moieties (diarylamine, carbazole, azepine, and dibenzazepine) was investigated to understand their photophysical and photoelectrochemical properties by employing density functional theory (DFT) and time-dependent DFT. It is experimentally proved that BODIPY enhances light-harvesting in the red and near IR regions of visible light. Electron density distribution analysis was performed for all the dyes to confirm the intramolecular charge transfer, envisioned from the simulated absorption spectra of the dyes. Carbazole donor-based dyes exhibited the lowest reorganization energy. A dye attached to the TiO2(1 0 1) surface was modeled to estimate the adsorption energy of the dyes. The density of states analysis revealed that the absence of defect states in the bandgap of TiO2 facilitates smooth electron transfer from the excited state of the dye to the conduction band of TiO2. Considering the lowest unoccupied molecular orbital (LUMO) energy level of the dyes and the conduction band energy level of TiO2, it is understood that all the dyes studied in this report are capable of electron injection upon photoexcitation. Considering the driving force for dye regeneration and the magnitude of reorganization energy, a carbazole donor-based dye (D2) would be the best performing dye in DSSCs. Previously, the power conversion efficiencies of the dyes have been reported, and the carbazole donor-based dye (D2) exhibited the highest efficiency among all the dyes. Our computational investigations are in good agreement with the experimental results.
18 citations
TL;DR: In this paper, cycloalkyl moieties were proposed to stop the participation in the resonance of the lone pair with the other two phenyl rings so that the available lone pair on N will be pumped towards acceptor to achieve an efficient intramolecular charge transfer.
Abstract: In this study, five dyes comprising different donor moieties were proposed with a new design approach. In the triphenylamine (TPA) moiety, the lone pair electron on N takes part in resonance with three phenyl rings. As a result, the donating ability of TPA decreases in TPA-based dyes and hence the intramolecular charge transfer (ICT). We have proposed cycloalkyl moieties in place of phenyl moieties to stop the participation in the resonance of the lone pair with the other two phenyl rings so that the available lone pair on N will be pumped towards acceptor to achieve an efficient ICT. All dyes were subjected to density functional theory (DFT) and time-dependent DFT to evaluate their ground and excited-state properties. The projected density of state and natural bond orbital analyses were carried out to confirm the ICT from the donor to the acceptor moiety and also to comprehend the donating ability of the newly proposed donor moieties. The reorganization energy of the dyes was calculated to find out the conformational changes that occurred during photoexcitation. The dyes were attached to (1 0 1) anatase surface of TiO2 to understand the electron transfer from the excited-state of the dye to the conduction band of the TiO2. The adsorption energy of the dyes onto the (1 0 1) anatase surface of the TiO2 was also evaluated. The absence of defect states in the density of states spectrum indicated the smooth electron transfer at the dye/TiO2 interfaces.
15 citations
15 citations
TL;DR: In this article, the synthesis and conductive properties of a low molecular weight cyclic organoboron crystalline electrolyte was studied in anodic half-cell configuration of a Li ion secondary battery.
Abstract: Conduction mechanisms in solid polymer electrolytes of Li ion batteries have always been a concern due to their theoretical limitation in conductivity value. In an attempt to increase the ionic conductivity of solid state electrolytes, used in lithium ion secondary batteries (LiBs), we studied the synthesis and conductive properties of a low molecular weight cyclic organoboron crystalline electrolyte. This electrolyte was expected to show better electrochemical properties than solid polymer electrolytes. The electrolyte was doped with LiTFSI salt via two different methods viz. (1) facile grinding of the crystalline sample with lithium salt under a nitrogen atmosphere and (2) a conventional method of solvent dissolution and evaporation under vacuum. The electrochemical properties were studied under specific composition of Li salt. The presence of crystallinity in the electrolyte can be considered as an important factor behind the high ionic conductivity of an all solid electrolyte of this type. Charge–discharge properties of the cell using the electrolyte were investigated in anodic half-cell configuration.
10 citations
TL;DR: In this article, a series of tailored aryl acyclic (biphenyl, dye 1 and 2), cyclic (phenanthrene, dye 3 and 4) and methyl-substituted (dye 5) imidazole derivatives were synthesized and characterized for application in dye-sensitized solar cells (DSSCs).
Abstract: A series of systematically tailored aryl acyclic (biphenyl, dye 1 and 2), cyclic (phenanthrene, dye 3 and 4) and methyl-substituted (dye 5) imidazole derivatives were synthesized and characterized for application in dye-sensitized solar cells (DSSCs). The anisole ancillary donor was attached to the –NH position in the imidazole center to obtain dyes 2 and 4. Cyclic voltammetry and UV-visible studies of all the dyes indicate their suitability for DSSC applications. Among the as-synthesized dyes, dye 4 with a phenanthrene donor and anisole ancillary donor showed the highest power conversion efficiency (PCE) of 7.16% (JSC = 13.07 mA cm−2, VOC = 0.831 V, FF = 0.659). Dye 2 displayed the highest electron lifetime in the conduction band of the photoanode; hence, the open circuit voltage of the DSSC based on dye 2 was the highest among the studied dyes (0.865 V). By using a novel potential-assisted dye staining process, the dye loading on the photoanode was enhanced by 18% in 1 h, which in turn enhanced the PCE to 8.10%.
9 citations
TL;DR: In this article, two pyrene-carbazole dyes bearing single bond (PC1) and double bond spacer (PC2) linkers and cyano-acrylic acid as an acceptor were synthesized.
Abstract: Both carbazole and pyrene are electron-rich aromatic systems and are expected to be potential donors when used in a push–pull dye architecture in the field of DSSC technology. Herein, two novel pyrene–carbazole dyes bearing single bond (PC1) and double bond (PC2) linkers and cyano-acrylic acid as an acceptor were synthesized. The dye with a double bond spacer (PC2) in the presence of CDCA achieved an improved power conversion efficiency of 6.30% with a short circuit current of 11.59 mA cm−2, open circuit potential (VOC) of 0.80 V, and a fill factor of 0.68 under standard global AM 1.5G solar conditions. Cyclic voltammetry and density functional theory studies indicate that the incorporation of two donors improved the ease of oxidation of the dyes, which resulted in a high VOC. Despite having a rigid single bond, the charge transfer of the PC1 dye is found to be poor, which affected the photovoltaic performance. The dihedral angle measured at each joint of the optimized dye indicated that PC2 exhibits excellent intramolecular charge transfer due to the near planarity in the structure. Besides, the high electron lifetime in the excited state of PC2 makes it the best performer among the three dyes studied.
8 citations
30 Jun 2020
TL;DR: Synthesizing an active and stable ORR and oxygen evolution reaction (OER) electrocatalyst in cost effective way remains a challenge in fuel cells and rechargeable metal.
Abstract: Synthesizing an active and stable oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalyst in cost effective way remains a challenge in fuel cells and rechargeable metal-
6 citations
5 citations
TL;DR: In this paper, the 3MLCT state lifetimes of N719 and Z907 dyes were investigated with application of time-resolved absorption and emission, and the dynamics of the spectro-temporal data was determined with singlewavelength and global fitting.
Abstract: Excited-state properties of two novel metal-free custom-made dyes D2d [(Z)-2-cyano-3-(4-((E)-2-(6-(4-methoxyphenyl)-9-octyl-9H-carbazol-3-yl)vinyl)phenyl)acrylic acid] and T-SB-C [(E)-2-cyano-3-(4-((E)-4-(diphenylamino)styryl)phenyl)acrylic acid] and two commercially available Ruthenium-based N719 and Z907 dyes were investigated with application of time-resolved absorption and emission. Singlet excited state lifetimes of D2d and T-SB-C were determined in acetonitrile and are 1.4 and 2.45 ns, respectively. The 3MLCT state lifetimes of N719 and Z907 dyes determined in methanol are 9.25 and 8.85 ns, respectively. Subsequently, photoexcited processes like electron injection and charge recombination were studied for those dyes adsorbed on the FTO/TiCl4/TiO2 photoanodes and fabricated via a conventional staining technique and innovative potential-assisted fast dye staining method. The dynamics of the spectro-temporal data was determined with application of single-wavelength and global fitting. All dye-TiO2 systems showed fast picosecond injection of excited electrons to the conduction band of the TiO2 layer and in complex multiphasic charge recombination processes. The dynamics of those processes is not altered by the dye adsorption method.
3 citations
TL;DR: In this paper, a dye-sensitized solar cells (DSSCs) made of dye stained TiO2 semiconductor photoanode was fabricated using a quick and novel electrosorption assisted dye-staining process.
2 citations
16 Nov 2020
TL;DR: In this paper, a hierarchical porous architecture was imparted to the TiO2 photoanode using size-selected (1.5 to 3 nm) carbon nanomaterials (CNMs).
Abstract: Dye-sensitized solar cells are economical and easy to fabricate in comparison to silicon-based solar cells. The visible light sensitizer dye is the main component of DSSCs, the performance of which can be enhanced if the TiO2 semiconductor is engineered to maximize the utilization of the dye together with its easy regeneration from its oxidized form. In this study, a hierarchical porous architecture was imparted to the TiO2 photoanode using size-selected (1.5 to 3 nm) carbon nanomaterials (CNMs). This porous structure enhanced the accessibility of the dye to the electrolyte. Using the N719 dye as a model system, the effect of the hierarchical porous structure was demonstrated. The inclusion of CNMs together with TiO2 enhanced the short circuit current density by 31% and power conversion efficiency (PCE) by 46% compared to the CNM-free DSSCs.
TL;DR: In this article, a modified glassy carbon electrode with a copper-1-amino-2-naphthol (AN−Cu2+) complex immobilized on a carboxyl-functionalized multiwalled carbon nanotube (f-MWCNT) was employed for the electrochemical detection of dissolved oxygen (DO) in 0.1 mol L−1 phosphate buffer solution.
Abstract: Herein, we account for a modified glassy carbon electrode with a copper-1-amino-2-naphthol (AN–Cu2+) complex immobilized on a carboxyl-functionalized multiwalled carbon nanotube (f-MWCNT) (GCE/f-MWCNT@AN–Cu2+). It is employed for the electrochemical detection of dissolved oxygen (DO) in 0.1 mol L−1 phosphate buffer solution (PBS). The oxygen reduction reaction was exclusively catalyzed by the AN coated f-MWCNT. Cu2+ was merely used to immobilize AN on the f-MWCNT to enhance the stability of the electrode. To prove the interaction between O2 and AN, a dilute solution of AN in pH 7 PBS was monitored by purging N2 and O2, and an intense turbidity was observed, with O2 indicating the adduct formation between AN and O2. The prepared sensor exhibits an excellent tolerance to interferents which are found in water samples along with oxygen. The Koutecky-Levich analysis confirms the four-electron reduction of O2. Moreover, reproducibility, stability, the limit of detection (LOD), and sensitivity of the modified electrode were found to show the capability of the proposed sensor for monitoring the DO content.