In
this research, photovoltaic properties of the indoloquinoxaline-based
dyes QX22–QX25 as the (D)2-A−π–A
structure were investigated dynamically and kinetically. In these
structures, two acceptors cyanoacrylic acid and 2-(1,1-dicyanomethylene)rhodanine,
CCRD, and two π-spacers furan and thiophene have been used.
Density functional theory (DFT), time-dependent DFT (TD-DFT), and
natural bond orbital (NBO) were used to evaluate the electronic structures
and excited state properties of these metal-free organic dyes. The
analysis of the dynamics/kinetics of the photovoltaic parameters of
the corresponding dye-sensitized solar cells (DSSCs) shows that each
moiety of the D−π–A system has a more specific
effect on one of the photovoltaic properties. On the basis of the
obtained results, linear correlations of the incident photon to current
conversion efficiency (IPCE) to the k
inj/ΔG
inj are stronger than that of
light harvesting efficiency (LHE). Moreover, a red shift in the absorption
spectra and a higher LHE in the DCRD-based dyes are observed. Although
thiophene-based dyes showed an improved exciton dissociation rate, R
d, QX22 and QX23 are the preferred candidates
to be applied in solar cells due to their optimized quantum chemistry
properties and maximum IPCE.
In this work, kinetics and dynamics of the functionality of indoloquinoxaline-based dye-sensitized solar cells (DSSCs), QX22− QX25, were investigated in gas and solvent media. Quantum chemistry properties of the dyes at the excited states show that each moiety of the (D) 2 −A−π−A system has a specific effect on the photovoltaic properties. Solvent effect analysis shows that among ethanol, toluene, tetrahydrofuran, and methylene dichloride, toluene is the preferred medium for intra-/intermolecular charge transfer, dynamically and kinetically. Moreover, the behavior of the light harvesting efficiency (LHE) and incident photon-to-current efficiency (IPCE) are not similar, due to a strong effect of the Gibbs energy of electron injection on the energy conversion efficiency. Finally, the dye composed of −COOH as the anchoring group and thiophene as the π-spacer is the best candidate to be applied in DSSC due to its better efficiency originated from a lower electrophilicity and electronic chemical potential.
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