@article {43878, title = {Mixed-stack charge transfer crystals of pillar[5]quinone and tetrathiafulvalene exhibiting ferroelectric features}, journal = {Chemistry- A European Journal }, volume = {23}, year = {2017}, month = {SEP}, chapter = {12630-12635}, abstract = {

Ferroelectric materials find extensive applications in the fabrication of compact memory devices and ultra-sensitive multifunctional detectors. Face-to-face alternate stacking of electron donors and acceptors effectuate long-range unidirectional ordering of charge-transfer (CT) dipoles, promising tunable ferroelectricity. Herein we report a new TTF-quinone system-an emerald green CT complex consisting pillar[5]quinone (P5Q) and tetrathiafulvalene (TTF). The CT crystals, as determined by single crystal synchrotron X-ray diffraction, adopt a 1:1 mixed-stack arrangement of donor and acceptor with alternating dimers of TTF and 1,4-dioxane encapsulated P5Q. The TTF-P5Q.dioxane crystal possesses a macroscopic polarization axis giving rise to ferroelectricity at room temperature. The CT complex manifests ferroelectric features such as optical polarization rotation, temperature-dependent phase transition and piezoelectric response in single crystals. Ferroelectric behavior observed in P5Q-based CT complex widens the scope for further work on this structurally intriguing and readily accessible cyclic pentaquinone.

}, keywords = {Acceptor, Charge-transfer complexes, Chemistry, Conductors, DDQ, Donor, ferroelectric, Macrocycles, Organic Metals, Pi-interaction, Pillar[5]quinone, salts, Transfer Complexes, Transport}, issn = {0947-6539}, doi = {10.1002/chem.201702577}, author = {Shivakumar, Kilingaru I. and Swathi, Kadaba and Goudappagouda and Das, Tamal C. and Kumar, Ashwani and Makde, Ravindra D. and Vanka, Kumar and Narayan, Kavassery S. and Babu, Sukumaran Santhosh and Sanjayan, Gangadhar J.} } @article {48941, title = {Steric and electronic effect in unsymmetrical squaraine dyes for dye-sensitized solar cells}, journal = {Journal of physical chemistry C }, volume = {127}, year = {2023}, month = {NOV}, pages = {22473-22488}, type = {Journal Article}, abstract = {

Functionalizing the light harvesting sensitizers with additional electron-donating or -withdrawing groups is a potential approach to modulate the photophysical and electrochemical properties which in-turn optimizes the driving force associated with the charge injection and dye-regeneration processes at the dye-TiO2/electrolyte interface and the photovoltaic device performance in dye-sensitized solar cells (DSSCs). Furthermore, modulated electronic levels of the dyes provide an opportunity to reduce the overpotential associated with the dye-regeneration process and make the dye-TiO2 interface compatible with various electrolytes. Furthermore, an in-built steric feature by means of introducing linear/branched alkyl groups in the sensitizer is important in controlling the aggregation of dyes on the TiO2 surface. Hence, to integrate both steric and electronic properties, a series of alkyl group-wrapped unsymmetrical squaraine dyes (SQ-X) with electron-donating and -withdrawing groups have been designed, synthesized, and utilized for DSSC device fabrication. These dyes are functionalized with alkyl groups at both sp(3)-C and N-atoms of the indoline donor moiety at the nonanchoring side to have a similar steric feature. Photophysical and electrochemical studies revealed that the HOMO and LUMO energy levels of the SQ-X series of dyes have been modulated systematically with sufficient driving forces for both charge injection and dye-regeneration processes with iodolyte (I-/I-3(-)) electrolyte. In the presence of electron-donating groups in SQ-X (where X = -NPh2 and -OMe), the HOMO energy levels are less positive than SQ-H, whereas the presence of electron-withdrawing groups such as -CO2Me, -CN, and -NO2 pushed the HOMO energy levels toward more positive potentials. Enhanced photovoltaic performances have been obtained for the dyes containing electron-donating groups, where the dye with the -NPh2 group showed a maximum of eta 7.03\% (V-OC 708 mV, J(SC) 13.16 mA cm(-2), and ff 78\%). The dye with the strong electron-withdrawing group -NO2 showed an efficiency of 1.49\% (V-OC = 634 mV, J(SC) = 3.13 mA cm(-2), and ff 75\%). As the dyes with the electron-withdrawing group possess deep positive HOMO energy levels, the DSSC device characterization has been investigated with the Cu+/2+ redox shuttle. The reduced device performance of electron-withdrawing-group-containing dyes is due to the unfavored charge distribution in the LUMO compared to the presence of electron-donating-group-containing dyes, and it was supported by the difference in the charge injection efficiency.

}, keywords = {cobalt, Donor, Dynamics, Organic dyes}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.3c05222}, author = {Nawghare, Indrajeet S. and Singh, Ambarish Kumar and Maibam, Ashakiran and Krishnamurty, Sailaja and Krishnamoorthy, Kothandam and Nithyanandhan, Jayaraj} }