Performance Regulation of Thieno[3,2-b]benzothiophene π-Spacer-Based D-π-A Organic Dyes for Dye-Sensitized Solar Cell Applications: Insights From Computational Study

Abstract

Dye-sensitized solar cells (DSSCs) have been widely investigated; however, the development of promising dye sensitizers is still appealing. In this work, we perform a detailed theoretical search for high-efficiency D-π-A organic dyes using density functional theory and time-dependent density functional theory calculations. Specifically, we perform geometric optimization, and electronic structure and absorption spectra calculations for isolated dyes for two thieno[3,2-b]benzothiophene π-spacer-based D-π-A organic dyes SGT129 and SGT130, which show significant efficiency difference, before and after binding to a TiO2 semiconductor. The calculation results reveal that the coplanar configuration between the electron donor and the π-spacer can enhance electronic communication efficiently, thus facilitating intra-molecular charge transfer from the electron donor to the acceptor groups in SGT130. The absorption spectrum of SGT130 broadens and is red-shifted owing to the decreased bandgap. The higher light-harvesting efficiency, favorable intra-molecular charge transfer, larger shift of the conduction band edge in the TiO2 semiconductor, and slower charge recombination between the injected electrons in the TiO2 conduction band and the electrolyte explain the superior efficiency of SGT130 over that of SGT129. Using SGT130 as the reference dye, we further design four novel dyes 1–4 by modifying the π-spacer with electron-rich and electron-withdrawing moieties. Judging from the theoretical parameters influencing the short-circuit current and open-circuit voltage, we found that all dyes would perform better than SGT130 in terms of the favorable interfacial charge transfer (ICT) and light-harvesting efficiency, as well as the larger shift of the TiO2 conduction band edge. Our theoretical research is expected to provide valuable insights into the molecular modification of TBT-based D-π-A organic dyes for DSSC applications.

Second-Order Nonlinear Optical Switch Manipulation of Photosensitive Layer by an External Electric Field Coupled with Graphene Quantum Dots

“…In addition to the research breakthrough in the experimental aspect, the theoretical calculation of quantum chemistry has also been deeply explored. − Recently, Xie et al simulated the photochemical and photophysical parameters of two sensitizers with different bridging parts by theoretical means and found that the structure of the bridging part between the electron donor and the π-spacer had a great influence on the performance of the sensitizer and that the bridging part with a coplanar structure was more beneficial to the optical performance of DSSC. He and collaborators used Zn-porphyrin as a building block to explore the effect of the Zn-porphyrin insertion position on the performance of the sensitizer, and the results showed that Zn-porphyrin close to the acceptor group was more conducive to the electron transfer of DSSC and could significantly increase the short-circuit current density.…”

Tuning the Optoelectronic Properties of Cross Conjugated Small Molecules Using Benzodithiophene As a Core Unit With Favorable Photovoltaic Parameters

“…A high value of V OC depends on the greater difference between the bandgap energy of HOMO and LUMO by keeping the HOMO at a low energy level and LOMO at a high energy level [44][45][46][47]. The energy gap was calculated between HOMO of newly architecture cross conjugated donor molecules and LUMO of illustrious PC 61 BM acceptor material as shown in Fig.…”

Photoexcitation Processes in Oligomethine Cyanine Dyes for Dye-Sensitized Solar Cells—Synthesis and Computational Study

“…σ(λ) being the absorption cross section (in units of cm 2 /mol), obtained from the decadic extinction coefficient, ε(λ) (units of mol −1 •cm −1 ) by multiplication with 1000 cm 3 , and Γ is the number of moles of sensitizer per square centimetre of projected surface area of the film [10,77,78]. We note that the calculation of the short-circuit current density is not trivial, as the functions under the integral in Equation 6are not easily available.…”

“…We note that the calculation of the short-circuit current density is not trivial, as the functions under the integral in Equation 6are not easily available. The solar photon flux is accessible [79] and has recently been used [78], although in other reports, the solar photon flux was approximated based on Planck's blackbody radiation approximation [80,81]. One challenge is to determine theoretically the electron injection, dye regeneration and charge collection efficiencies.…”

“…The injection efficiency depends on the driving force, ∆G inj , with claims that for large values it tends to 1 [82]. In many cases, simplifying assumptions are made, for instance, claiming that the maximum photocurrent can be obtained if the efficiencies in Equation (6) were equal to 1 [78]. A more rigorous approach should take into account the various relaxation times of the processes involved [83,84].…”