Theoretical Study of the Effect of π-Bridge on Optical and Electronic Properties of Carbazole-Based Sensitizers for DSSCs

Abstract

Eight novel metal-free organic sensitizers were proposed for dye-sensitized solar cells (DSSCs), theoretically calculated and studied via density functional theory with D-π-A structure. These proposals were formed to study the effect of novel π-bridges, using carbazole as the donor group and cyanoacrylic acid as the anchorage group. Through the M06/6-31G(d) level of theory, ground state geometry optimization, vibrational frequencies, the highest occupied molecular orbital, the lowest unoccupied molecular orbital, and their energy levels were calculated. Further, chemical reactivity parameters were obtained and analyzed, such as chemical hardness (η), electrophilicity index (ω), electroaccepting power (ω+) and electrodonating power (ω-). Free energy of electron injection (ΔGinj) and light-harvesting efficiency (LHE) also were calculated and discussed. On the other hand, absorption wavelengths, oscillator strengths, and electron transitions were calculated through time-dependent density functional theory with the M06-2X/6-31G(d) level of theory. In conclusion, the inclusion of thiophene groups and the Si heteroatom in the π-bridge improved charge transfer, chemical stability, and other optoelectronic properties of carbazole-based dyes.

Electronic and optical properties’ tuning of phenoxazine-based D-A2-π-A1 organic dyes for dye-sensitized solar cells. DFT/TDDFT investigations

“…This gave access to the easy calculation of molecular orbital and energies. The chemical reactivity parameters such as chemical hardness, electrophilicity index, electrodonating power, and electroaccepting power were calculated using DFT conceptual as reported by Delgado-Montiel [ 43 , 44 ]. The UV-Vis spectra of the geometries were evaluated using TD-DFT with B3LYP and 6-31G∗∗ theory [ 23 , 45 ] using conductor like polarizable continuum solvation model in the gas phase; which is considered sufficient for the prediction of absorption spectra [ 46 , 47 ].…”

Directional Exciton Migration in Benzoimidazole-Based Metal–Organic Frameworks

“…This difference in delocalization may contribute to the 100 nm shift in the absorption and emission spectra. Such a large spectral shift was also observed in other fluorophores with heteroaromatic rings . The effect of specific linker-solvent interactions (i.e., hydrogen-bond formation) on the optical properties were analyzed through the Laplacian bond order (LBO), which directly reflects the strength of a particular interaction between two atoms .…”

“…Such a large spectral shift was also observed in other fluorophores with heteroaromatic rings. 35 The effect of specific linker-solvent interactions (i.e., hydrogen-bond formation) on the optical properties were analyzed through the Laplacian bond order (LBO), which directly reflects the strength of a particular interaction between two atoms. 36 The LBO changes in Figure 2d show a decrease in the bond strength going from water to methanol and acetonitrile for H 2 BI and H 2 TD linkers.…”

Rational Design of Broadly Absorbing Boron Dipyrromethene-Carbazole Dyads for Dye-Sensitized Solar Cells: A DFT Study

“…Montiel et al designed metal-free organic dyes with carbazole as the donor unit and cyanoacrylic acid as the acceptor groups. They introduced various π bridges and performed a theoretical study on the electronic properties of the dyes . Velayudhan et al.…”

“…They introduced various π bridges and performed a theoretical study on the electronic properties of the dyes. 16 Velayudhan et al performed a computational study on the photoelectrochemical properties of a series of designed dyes with butadiene unit as the π spacer and cyanoacrylic acid group as the acceptor. They focused on the influence of various electron-rich nitrogen-donating groups on the performance of the dyes.…”