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<p>In this work, four Zinc-porphyrin (ZnP)-based donor-π-acceptor (D-π-A) dyes, namely Dye-A, Dye-B, Dye-C, and Dye-D, incorporating a dicyclobuta[a, d]benzene acetylene linker are systematically investigated for dye-sensitized solar cell (DSSC) applications using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The designed structures exhibit favourable frontier molecular orbital alignment, with LUMO levels positioned above the TiO<sub>2</sub> conduction band and HOMO levels below the electrolyte redox potential, ensuring efficient electron injection and dye regeneration. The dyes show relatively small energy gaps (0.915–1.450&#xa0;eV), indicating good charge transfer capability. Excited-state analysis reveals that the first three dyes, Dye-A to Dye-C predominantly indicate local excitation transition with partial charge transfer character, whereas Dye-D demonstrates clear long-range charge transfer, supported by positive <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({t}_{\text{i}\text{n}\text{d}\text{e}\text{x}}\)</EquationSource> </InlineEquation>, higher <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({D}_{\text{i}\text{n}\text{d}\text{e}\text{x}}\)</EquationSource> </InlineEquation>, lower excitonic binding energy <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\({E}_{\text{b}}\)</EquationSource> </InlineEquation>, and a larger charge transfer length. Optical studies indicate absorption in the UV-visible region, with Dye-D showing a red-shifted absorption (470.778&#xa0;nm), suggesting enhanced light-harvesting ability. Photovoltaic analysis further confirms favourable electron injection (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\varDelta{G}_{\text{i}\text{n}\text{j}\text{e}\text{c}\text{t}}\:\)</EquationSource> </InlineEquation>= 5.793-6.200&#xa0;eV) and good light-harvesting efficiencies, particularly for dyes A, B and D. Overall, the results highlight Dye-D as a promising sensitizer due to its superior charge transfer characteristics and extended visible light absorption, while the study establishes the effectiveness of dicyclobuta[a, d]benzene acetylene linkers in improving DSSC performance.</p>

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Dicyclobuta[a, d]benzene-acetylene-bridged Zn-porphyrin donor-π-acceptor dyes: a DFT study for enhanced charge transfer in DSSCs

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • Barsha Pal,
  • Utpal Sarkar

摘要

In this work, four Zinc-porphyrin (ZnP)-based donor-π-acceptor (D-π-A) dyes, namely Dye-A, Dye-B, Dye-C, and Dye-D, incorporating a dicyclobuta[a, d]benzene acetylene linker are systematically investigated for dye-sensitized solar cell (DSSC) applications using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The designed structures exhibit favourable frontier molecular orbital alignment, with LUMO levels positioned above the TiO2 conduction band and HOMO levels below the electrolyte redox potential, ensuring efficient electron injection and dye regeneration. The dyes show relatively small energy gaps (0.915–1.450 eV), indicating good charge transfer capability. Excited-state analysis reveals that the first three dyes, Dye-A to Dye-C predominantly indicate local excitation transition with partial charge transfer character, whereas Dye-D demonstrates clear long-range charge transfer, supported by positive \({t}_{\text{i}\text{n}\text{d}\text{e}\text{x}}\) , higher \({D}_{\text{i}\text{n}\text{d}\text{e}\text{x}}\) , lower excitonic binding energy \({E}_{\text{b}}\) , and a larger charge transfer length. Optical studies indicate absorption in the UV-visible region, with Dye-D showing a red-shifted absorption (470.778 nm), suggesting enhanced light-harvesting ability. Photovoltaic analysis further confirms favourable electron injection ( \(\varDelta{G}_{\text{i}\text{n}\text{j}\text{e}\text{c}\text{t}}\:\) = 5.793-6.200 eV) and good light-harvesting efficiencies, particularly for dyes A, B and D. Overall, the results highlight Dye-D as a promising sensitizer due to its superior charge transfer characteristics and extended visible light absorption, while the study establishes the effectiveness of dicyclobuta[a, d]benzene acetylene linkers in improving DSSC performance.