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Context <p>Three novel <i>D</i>‑π<sub>1</sub>‑π<sub>2</sub>‑<i>A</i> organic dyes with polyheterocyclic <i>π</i><sub>2</sub>‑bridges and cyano‑modified acceptors were designed to amplify the polarity contrast between the terminal groups. Density functional theory (DFT) calculations were used to characterize the energy levels, absorption spectra, and intramolecular charge transfer (ICT) characteristics, with a focus on the regulatory effects of different electron‑withdrawing substituents on electron injection, dye regeneration, and charge recombination at the dye@TiO<sub>2</sub> interface. Simulation results indicate that SGT-149-3 exhibits the best photovoltaic performance, which can be attributed to two key structural optimizations: the replacement of the <i>π</i><sub>2</sub>-bridge with dithienothiophene and the rational modification of the acceptor with cyano group. The narrow energy gap leads to a significant redshift of 112.21&#xa0;nm in the absorption spectrum compared to the reference dye SGT-149. The enhanced ICT effect improves the separation efficiency of photogenerated carriers, while stronger covalent interactions with TiO<sub>2</sub> substrates and prolonged fluorescence lifetime suppress charge recombination. The short-circuit current density and photoelectric conversion efficiency of SGT-149-3 reach 28.53&#xa0;mA/cm<sup>2</sup> and 25.831%. Such exceptional photovoltaic parameters validate the latent application in photovoltaic devices. This work reveals the structure–property relationship between <i>π</i>-bridge engineering and acceptor modification, providing guidance for the rational design of high-efficiency dye-sensitized solar cells (DSSCs) sensitizers.</p> Methods <p>The ground-state geometries of all dye molecules were optimized at the B3LYP/6-311&#xa0;g(d,p) level of DFT. The excited-state properties were calculated using the CAM-B3LYP/6-311&#xa0;g(d,p) level of TD-DFT. For the dye@TiO<sub>2</sub> and dye@I systems, the 6-311&#xa0;g(d,p) basis set was used for light atoms (C, H, O, N, S), while the LANL2TZ(f) pseudopotential basis set was applied to Ti and I atoms. The geometries of these complexes were optimized at the B3LYP level. All the simulations were conducted in THF solution using the SMD solvent model. This study employed the Gaussian 16 software package as the core computational tool. Multiwfn_3.8 was used to analyze the <i>π</i>-electron delocalization and charge transfer characteristics.</p>

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Amplifying polarity contrast in D‑π1‑π2‑A dyes: Heterocyclic replacement combined with cyano modification for high-eficiency dye-sensitized solar cells

  • 期刊论文

  • 发表日期：

    2026年7月18日

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  • Jia Wei,
  • Jiadi Peng,
  • Kaidong Zhang,
  • Ruhang Zhang,
  • Linpo Yang,
  • Xingzhi Wu,
  • Yinglin Song

摘要

Context

Three novel D‑π1‑π2‑A organic dyes with polyheterocyclic π2‑bridges and cyano‑modified acceptors were designed to amplify the polarity contrast between the terminal groups. Density functional theory (DFT) calculations were used to characterize the energy levels, absorption spectra, and intramolecular charge transfer (ICT) characteristics, with a focus on the regulatory effects of different electron‑withdrawing substituents on electron injection, dye regeneration, and charge recombination at the dye@TiO2 interface. Simulation results indicate that SGT-149-3 exhibits the best photovoltaic performance, which can be attributed to two key structural optimizations: the replacement of the π2-bridge with dithienothiophene and the rational modification of the acceptor with cyano group. The narrow energy gap leads to a significant redshift of 112.21 nm in the absorption spectrum compared to the reference dye SGT-149. The enhanced ICT effect improves the separation efficiency of photogenerated carriers, while stronger covalent interactions with TiO2 substrates and prolonged fluorescence lifetime suppress charge recombination. The short-circuit current density and photoelectric conversion efficiency of SGT-149-3 reach 28.53 mA/cm2 and 25.831%. Such exceptional photovoltaic parameters validate the latent application in photovoltaic devices. This work reveals the structure–property relationship between π-bridge engineering and acceptor modification, providing guidance for the rational design of high-efficiency dye-sensitized solar cells (DSSCs) sensitizers.

Methods

The ground-state geometries of all dye molecules were optimized at the B3LYP/6-311 g(d,p) level of DFT. The excited-state properties were calculated using the CAM-B3LYP/6-311 g(d,p) level of TD-DFT. For the dye@TiO2 and dye@I systems, the 6-311 g(d,p) basis set was used for light atoms (C, H, O, N, S), while the LANL2TZ(f) pseudopotential basis set was applied to Ti and I atoms. The geometries of these complexes were optimized at the B3LYP level. All the simulations were conducted in THF solution using the SMD solvent model. This study employed the Gaussian 16 software package as the core computational tool. Multiwfn_3.8 was used to analyze the π-electron delocalization and charge transfer characteristics.