02184nas a2200241   4500008004100000022001400041245015900055210006900214260005700283300000800340490000700348520129500355653000801650653003101658653001701689653002001706653001101726100002401737700002001761700001701781700002301798856012101821       2016                        eng d  a1610-294000aDoes the position of the electron-donating nitrogen atom in the ring system influence the efficiency of a dye-sensitized solar cell? A computational study0 aDoes the position of the electrondonating nitrogen atom in the r  a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcJUN  a1210 v223 a<p>We have reported a number of new metal-free organic dyes (2-6) that have cyclic asymmetric benzotripyrrole derivatives as donor groups with peripheral nitrogen atoms in the ring, fluorine and thiophene groups as pi-spacers, and a cyanoacrylic acid acceptor group. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were employed to examine the influence of the position of the donor nitrogen atom and pi-conjugation on solar cell performance. The calculated electron-injection driving force (Delta G(inject)), electron-regeneration driving force (Delta G(regen)), light-harvesting efficiency (LHE), dipole moment (mu(normal)), and number of electrons transferred (Delta q) indicate that dyes 3, 4, and 6 have significantly higher efficiencies than reference dye 1, which exhibits high efficiency. We also extended our comparison to some other reported dyes, 7-9, which have a donor nitrogen atom in the middle of the ring system. The computed results suggest that dye 6 possesses a higher incident photon to current conversion efficiency (IPCE) than reported dyes 7-9. Thus, the use of donor groups with peripheral nitrogen atoms appears to lead to more efficient dyes than those in which the nitrogen atom is present in the middle of the donor ring system.</p>10aDFT10aDye-sensitized solar cells10aOrganic dyes10aPosition effect10aTD-DFT1 aBiswas, Abul, Kalam1 aBarik, Sunirmal1 aDas, Amitava1 aGanguly, Bishwajit  uhttp://library.ncl.res.in/content/does-position-electron-donating-nitrogen-atom-ring-system-influence-efficiency-dye03452nas a2200253   4500008004100000022001400041245009600055210006900151260000800220300001600228490000800244520261200252653001102864653001002875653001302885653001702898100002802915700002702943700002202970700002602992700003003018700002703048856012303075       2023                        eng d  a1932-744700aSteric and electronic effect in unsymmetrical squaraine dyes for dye-sensitized solar cells0 aSteric and electronic effect in unsymmetrical squaraine dyes for  cNOV  a22473-224880 v1273 a<p>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.</p>
10acobalt10aDonor10aDynamics10aOrganic dyes1 aNawghare, Indrajeet, S.1 aSingh, Ambarish, Kumar1 aMaibam, Ashakiran1 aKrishnamurty, Sailaja1 aKrishnamoorthy, Kothandam1 aNithyanandhan, Jayaraj  uhttp://library.ncl.res.in/content/steric-and-electronic-effect-unsymmetrical-squaraine-dyes-dye-sensitized-solar-cells