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[Display omitted] • A novel NSGDs/TiO 2 S-scheme heterojunction was successfully constructed. • TiO 2 possesses an urchin-like morphology with open mesoporous structure. • NSGDs offers better light absorption and photo-induced charge carriers' separation. • S-scheme heterojunction exhibits excellent photoactivity for toluene removal. In this study, we have considered a range of metal-free organic dyes with benzimidazole incorporated quinoline donors (BZQ) were designed with the configuration of Donor-Donor-π spacer-Acceptor (D-D-π-A). The impact of various π-spacer groups on their performance in dye-sensitized solar cells (DSSCs) was analyzed. The utilization of density functional theory (DFT) and time-dependent DFT (TD-DFT) methods has been employed in the examination of various aspects of electronic and absorption properties. The electronic absorption spectrum exhibits a red shift when the π spacer is increased, at the same time the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) was reduced. Theoretical calculations of these dyes demonstrated that altering the π-spacer group can result in several beneficial effects on the photovoltaic performance. [ABSTRACT FROM AUTHOR]

The geometries, electrostatic potential, Mulliken charge analysis, Natural Bond Orbital analysis and polarizabilities of propyl-para-hydroxybenzoate were calculated using B3LYP functional with 6-311++G(d,p) basis set. The calculated geometries are well matched with the experimental values. The Mullliken atomic charge analysis shows that the eventual charges are contained in the molecule. The NBO analysis explains the intramolecular charge transfer in the PHB molecule. The bonding features of the molecule were analyzed with the aid of Hirshfeld surface analysis. The frontier molecular orbital analysis showed the charge transfer obtained within the molecule. The calculated hyperpolarizability of the PHB molecule was 6.977E −30 esu and it was 8.9 times that of standard urea molecule. [ABSTRACT FROM AUTHOR]

The metal free organic sensitizers for dye sensitized solar cells (DSSC) have been developed from carbazole donor based on D-π-A architecture. From the structural modifications, the optical and electronic properties of the dyes were tuned. In the present investigation series of carbazole donor based metal free dyes were studied using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The optimized geometry, frontier molecular orbitals, energy levels and electronic absorption spectra were studied. The natural bond orbital analysis (NBO) gives the net electron transfer from the donor to acceptor. The electrochemical properties and light harvesting efficiency of the designed dye sensitizers were calculated. The π spacer increase induced the absorption peak and red shift was noted. The life time was increased by adding phenyl ring in the donor side. Based on theoretical calculations designed dye molecules are evaluated for DSSC application. Image 1 • Carbazole based novel dyes were designed through molecular engineering. • The π spacer effect was explored. • The π spacer increases lead to a red shift in the absorption peak. • The lifetime of sensitizers was tuned by substituting additional donor. [ABSTRACT FROM AUTHOR]

The structural and electronic properties of newly designed organic dyes have been examined by means of density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The ground state molecular structures of the designed dyes are fully optimized by DFT calculation in the gas phase. Electronic absorption characteristics are predicted by the TD-DFT calculation. The calculated electronic absorbance spectrum shows red shift if the donor is doubled. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy gap were decreased. The electronic and optical properties of the donor modified sensitizers were investigated by DFT and TD-DFT methods for dye sensitized solar cell (DSSC) application. [ABSTRACT FROM AUTHOR]

Twenty eight bi-anchored triphenylamine (TH-1 to TH-14) and phenyl modified triphenylamine (PH-TH-1 to PH-TH-14) based metal free organic dyes are designed for DSSC application. The electronic effect of different π-bridge configurations in donor-π-bridge-acceptor (D-π-A) 2 structure was theoretically simulated and verified using density functional theory (DFT) and time dependent density functional theory (TD-DFT). The triphenylamine and phenyl modified triphenylamine groups are used as donor and cyanoacrylic acid group is used as acceptor. Thiophene and cyanovinyl groups are used as π-bridge. The ground state molecular structure was optimized by density functional theory and the electronic absorption spectra were calculated by time dependent density functional theory. The light harvesting efficiency (LHE), dye regeneration energy (ΔG reg ) and electron injection energy (ΔG inject ) are determined by computational examination. It is observed that, when the number of π-bridge increases, the band gap of the dye decreases. Also the absorption maximum and molar extinction coefficient of the dyes are increased. Theoretical result shows that the thiophene-cyanovinyl and thiophene-thiophene-cyanovinyl–cyanovinyl configurations give broader and red shifted absorption spectrum compared to other configurations. Also the results of phenyl modified triphenylamine (PH-TH) dyes clearly show better absorption and dye regeneration energy compared to TH dyes. [ABSTRACT FROM AUTHOR]

The influence of different donor groups in quinoline based novel sensitizers for dye sensitized solar cell (DSSC) applications is analyzed by using density functional theory (DFT) and time dependent density functional theory (TD-DFT). Quinoline and donor functionalized quinoline based novel organic sensitizers have been designed with different π-spacers for DSSC applications. The ground state molecular structure of novel organic sensitizers is fully optimized by DFT calculation in both gas and chloroform phases. Electronic absorption characteristics are predicted by the TD-DFT calculation in both gas and chloroform phases. The polarizable continuum model is used for solvent phase optimization. The net electron transfer from the donor to acceptor is calculated from natural bond orbital (NBO) analysis. The injection energy and dye regeneration energy values are also calculated. Different donor groups are substituted in quinoline, and these substituted quinoline donors are used as the donor group. Cyanovinyl and thiophene groups act as π-spacers and cyanoacrylic acid acts as an acceptor. DFT and TD-DFT studies of the quinoline and donor functionalized quinoline sensitizers show that the coumarin based and N-hexyltetrahydroquinoline donors are more efficient for DSSC application. [ABSTRACT FROM AUTHOR]