Substituent effects on the croconate dyes in dye sensitized solar cell applications: a density functional theory study

Chitumalla, Ramesh Kumar,Lim, Manho,Gao, Xingfa,Jang, Joonkyung Springer-Verlag 2015 Journal of molecular modeling Vol.21 No.11

Density functional theory study on ruthenium dyes and dye@TiO₂ assemblies for dye sensitized solar cell applications

Chitumalla, Ramesh Kumar,Jang, Joonkyung Elsevier Science B.V., Amsterdam. 2018 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.159 No.-

<P><B>Abstract</B></P> <P>Cyclometalated ruthenium dyes improve significantly the performance of dye sensitized solar cells (DSSCs) based on conventional ruthenium dyes. Here, this study examined four thiocyanate-free cyclometalated ruthenium dyes using the density functional theory (DFT). The geometrical, electronic structural, and photophysical propertiesof the dyes and the dyes tethered to a TiO<SUB>2</SUB> surface were examined in both the presence and absence of an acetonitrile solvent. The Kohn-Sham eigenvalues of the molecular orbitals of the dyes were destabilized by <I>ca</I>. 2 eV in the presence of the solvent. The absorption peaks did not change significantly in position but hyperchromic shifts of more than two-fold occurred. When adsorbed on a TiO<SUB>2</SUB> surface, the dyes showed redshifted absorption of approximately 20 nm. To the best of our knowledge, a systematic and comprehensive first-principles investigation on cyclometalated ruthenium dyes in vacuum, solvent, and tethered to TiO<SUB>2</SUB> has been carried out for the first time.</P> <P><B>Highlights</B></P> <P> <UL> <LI> DFT study on cyclometalated Ru dyes in gas phase, solution, and on TiO<SUB>2</SUB>. </LI> <LI> Investigation of solvent effect on dyes and dye-sensitized TiO<SUB>2</SUB>. </LI> <LI> Destabilization of molecular orbitals of the dyes by 2 eV upon solvation. </LI> <LI> Dyes showed more than twofold hyperchromic shift in absorption in the solvent. </LI> <LI> Upon adsorption on TiO<SUB>2</SUB>, the dyes have shown a redshift of 20 nm in the absorption. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The dye interaction with solvent causes significant variations in their physical and chemical properties. The solvent in dye sensitized solar cells strongly affects the device efficiency and stability. The present study investigates the effect of acetonitrile solvent on the structural, electrochemical, and optical properties of four cyclometalated ruthenium dyes and dye@TiO<SUB>2</SUB> assemblies employing DFT/TDDFT and periodic-DFT methods. This study also investigates how anchoring of the dye on TiO<SUB>2</SUB> surface affects their electrochemical and photophysical behavior.</P> <P>[DISPLAY OMISSION]</P>

Effects of Cyclometalation on the Panchromatic Ruthenium Sensitizer for DSSC Applications

Ramesh Kumar Chitumalla,장준경 대한화학회 2017 Bulletin of the Korean Chemical Society Vol.38 No.10

Ruthenium sensitizers are promising materials for dye sensitized solar cells (DSSCs) and the concept of cyclometalation has been proposed to advance their performance. Density functional theory (DFT) simulations were performed to elucidate the electronic structure, electrochemical, and optical behavior of a cyclometalated ruthenium dye. The cyclometalated sensitizer has superior electrochemical properties (HOMO, LUMO, and bandgap) compared to its non-cyclometalated sensitizer. Upon cyclometalation, a remarkable improvement in the absorption across the UV–Visible and near-infrared regime has been observed. Furthermore, from the electron density contours of frontier molecular orbitals of dye attached TiO2, the charge transfer and sensitizing properties of the cyclometalated complex are superior to the corresponding non-cyclometalated ruthenium sensitizer. The density of states revealed the strong electronic coupling, which facilitates an effective electron injection into the semiconductor.

Chiral Pyrrolidine-Pyrazole Catalyzed Enantioselective Michael Addition: a Mechanistic Study by Computational Methods

Ramesh Kumar Chitumalla,Pavan Kumar Togapur,장준경 대한화학회 2016 Bulletin of the Korean Chemical Society Vol.37 No.10

Phenothiazine based blue emitter for light-emitting electrochemical cells

Shanmugasundaram, K.,Chitumalla, R.,Jang, J.,Choe, Y. Royal Society of Chemistry 2017 New journal of chemistry Vol.41 No.18

Computational studies of hole/electron transport in positional isomers of linear oligo-thienoacenes: Evaluation of internal reorganization energies using density functional theory

Thomas, A.,Chitumalla, R.K.,Puyad, A.L.,Mohan, K.V.,Jang, J. Elsevier Scientific Pub. Co 2016 Computational & theoretical chemistry Vol.1089 No.-

<P>The paper computationally investigates and compares the internal reorganization energies associated with the intermolecular transport of a hole and electron in a series of positional isomers of fused planar acenodithiophenes (S(n)a-c) with those of linear acenes (LA(n)). In particular, it is observed that, amongst the positional isomers, the para isomers (S(n)c) have got ultra-small reorganization energies than the other two positional isomers. The non-bonding character of frontier molecular orbitals (FMO) of these para isomers is the main reason for the existence of this phenomenon. Secondly, the nonbonding character in the FMO of these molecules is mediated by their open shell singlet biradical nature in ground state, as revealed by the Spin-flip time dependent density functional theory analysis. These aforementioned findings and characteristics of S(n)c series of molecules, strongly recommend that these molecules if synthesized will show high charge carrier mobility. Also we have revealed that biradicaloid nature of a molecule is new interesting design factor to achieve low reorganization energies. (C) 2016 Elsevier B.V. All rights reserved.</P>

Effectual binding of gallic acid with p-sulfonatocalix[4]arene: An experimental and theoretical interpretation

Saravanan, Chokalingam,Chitumalla, Ramesh Kumar,Ashwin, Bosco Christin Maria Arputham,Senthilkumaran, Marimuthu,Suresh, Palaniswamy,Jang, Joonkyung,Muthu Mareeswaran, Paulpandian Elsevier 2018 Journal of luminescence Vol.196 No.-

<P><B>Abstract</B></P> <P>The host-guest interaction of gallic acid (GA) with p-sulfonatocalix[4]arene (p-SC4) is studied using emission and excited state lifetime techniques. The quenching effect on the emission intensity and excited state lifetime is observed upon binding. The impact of oxidation potential upon binding is studied using cyclic voltammetric technique. The structural features and the mode of binding of GA with p-SC4 is examined using <SUP>1</SUP>H NMR and rotating frame overhauser effect spectroscopy (ROESY) techniques. The binding of GA with p-SC4 has also been examined by means of density functional theory simulations. The calculated interaction energy of GA with p-SC4 (22.15kcal/mol) indicates the strong binding nature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Formation of stable complex between GA and p-SC4 is studied in solution state. </LI> <LI> Quenching on emission intensity and lifetime of GA is observed upon addition of p-SC4. </LI> <LI> The downward potential shift is detected upon addition of GA on p-SC4 and vice versa. </LI> <LI> The <SUP>1</SUP>H NMR and ROESY spectral studies reveals that the GA is included into p-SC4. </LI> <LI> The theoretical simulations explains the intermolecular hydrogen bonding interactions between the GA and the p-SC4. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The comparative study of new carboxylated 1,3-indanedione sensitizers with standard cyanoacetic acid dyes using co-adsorbents in dye-sensitized solar cells

Jeong, Hyeonjun,Chitumalla, Ramesh Kumar,Kim, Dong Woo,Vattikuti, S.V. Prabhakar,Thogiti, Suresh,Cheruku, Rajesh,Kim, Jae Hong,Jang, Joonkyung,Koyyada, Ganesh,Jung, Jae Hak Elsevier 2019 Chemical physics letters Vol.715 No.-

<P><B>Abstract</B></P> <P>Two new carboxylated 1,3-indanedione sensitizers (MPhe-ind and BPhe-ind) were synthesized and their dye-sensitized solar cells (DSSC) performance were compared with the corresponding standard cyanoacetic acid sensitizers (MPhe-cn and BPhe-cn). The carboxylated 1,3-indanedione sensitizers have shown almost 100 nm enhanced absorption curves compared to the cyanoacetic acid dyes with an extended IPCE curve up to 800 nm. Despite greater absorption and electrochemical properties, the synthesized dyes showed moderate efficiencies (2.10% and 2.67%) than standard dyes. The low electron injection efficiency and recombination of carboxylated 1,3-indanedione might be responsible for low efficiency. Detailed investigation studies have been performed and complemented with the theoretical studies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The synthesized carboxylated 1,3-indanedione dyes DSSC performance were evaluated. </LI> <LI> The carboxylated 1,3-indanedione dyes showed 100 nm red-shifted absorption spectra. </LI> <LI> The IPCE of carboxylated 1,3-indanedione sensitizers have been extended upto 800 nm. </LI> <LI> The reasons for low efficiency of 1,3-indanedione sensitizers were discussed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The effect of carboxylated 1,3-indanedione anchoring group have been investigated and compared with standard cyanoacetic acid dyes for dye-sensitized solar cells application.</P> <P>[DISPLAY OMISSION]</P>

The impact of heteroatom substitution on cross-conjugation and its effect on the photovoltaic performance of DSSCs - a computational investigation of linear <i>vs.</i> cross-conjugated anchoring units

Paramasivam, Mahalingavelar,Chitumalla, Ramesh Kumar,Jang, Joonkyung,Youk, Ji Ho The Royal Society of Chemistry 2018 Physical chemistry chemical physics Vol.20 No.35

<P>The unusual bonding pattern and proximal heteroatom substitution in π-cross conjugation produced distinct changes in the energy levels and photophysical behaviour of the dyes. To seek an understanding of the origin of these fluctuations, we have carried out a detailed computational investigation on a series of D-π1-π2 (A1)-A2 structured dyes comprised of common donor-spacer (auxiliary acceptor) units but varied the anchoring parts. In this study, we introduced a novel dimethylamino substituted fluorene-based triarylamine donor unit and evaluated its donating strength. Based on the comparison of DFT computed energy levels with experimental results, we have proposed an orbital splitting pattern to explain the energy level and photophysical properties of the linear <I>vs.</I> cross-conjugated dyes with respect to the linking position of the anchoring unit and benzo[1,2,5]thiadiazole (BTD) substitution. The smallest HOMO-LUMO gap of B3 mainly originated from the weak overlap of the directionality mismatch of the orbital interaction imposed by cross-conjugation. The inefficient overlap in B3 can possibly influence the energy levels but failed to enhance the charge transfer transitions upon photoexcitation. On the other hand, β-heteroatom substitution in bridged dyes partially enhanced π-delocalization over the cross conjugation and produced a significant ICT absorption with an optoelectronic response in the NIR region. BTD acceptor substitution increased the HOMO-LUMO gap of the bridged dyes. NBO analysis was performed to corroborate our predictions. DOS-PDOS analysis of the dyes@TiO2 was employed to investigate the electron injection rate of linear <I>vs.</I> bridged dyes. The anchoring pattern and large torsional deviation of the carboxylate anchoring group upon TiO2 adsorption drastically decreased the photovoltaic performance of the bridged dyes. The results obtained from this study provided a detailed understanding of how to surmount the cross-conjugation with the aid of β-heteroatom substitution. These design guidelines would be helpful in developing novel NIR dyes with better hole mobility for various optoelectronic applications. Furthermore, π-delocalization over the cross-conjugation concept opens a new pathway in the field of functional molecular devices to increase the charge conductance over several orders of magnitude with a significant reduction of destructive quantum interference at the molecular junction.</P>

Density Functional Theory Study on the Cross-Linking of Mussel Adhesive Proteins

Matin, Mohammad A.,Chitumalla, Ramesh Kumar,Lim, Manho,Gao, Xingfa,Jang, Joonkyung American Chemical Society 2015 The Journal of physical chemistry B Vol.119 No.17

<P>The water-resistant adhesion of mussel adhesive proteins (MAPs) to a wet surface requires a cross-linking step, where the catecholic ligands of MAPs coordinate to various transition-metal ions. Fe(III), among the range of metal ions, induces particularly strong cross-linking. The molecular details underlying this cross-linking mediated by transition-metal ions are largely unknown. Of particular interest is the metal–ligand binding energy, which is the molecular origin of the mechanical properties of cross-linked MAPs. Using density functional theory, this study examined the structures and binding energies of various trivalent metal ions (Ti–Ga) forming coordination complexes with a polymeric ligand similar to a MAP. These binding energies were 1 order of magnitude larger than the physisorption energy of a catechol molecule on a metallic surface. On the other hand, the coordination strength of Fe(III) with the ligand was not particularly strong compared to the other metal ions studied. Therefore, the strong cross-linking in the presence of Fe(III) is ascribed to its additional ability as an oxidant to induce covalent cross-linking of the catecholic groups of MAPs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2015/jpcbfk.2015.119.issue-17/acs.jpcb.5b01152/production/images/medium/jp-2015-011524_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b01152'>ACS Electronic Supporting Info</A></P>