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<p>The present study investigates how organic pigments adhere to the TiO₂ surface, which acts as a mesoporous film in dye-sensitized solar cells (DSSCs). The effect of this adhesion on the electronic band gap is of interest. In this regard, eight different density functionals were evaluated to identify the most appropriate computational method to accurately describe the electronic and optical properties of TiO₂ nanoparticles. The results obtained for the absorption maximum (λ<sub>max</sub>) and band gap energy (E<sub>g</sub>) were compared with valid experimental data and it was found that the LSDA functional provides results closely matching benchmark values. Then, geometric optimization and time-dependent density functional theory (TD-DFT) calculations were performed on the adsorption of Naphthoquinone on TiO₂. These calculations identified two stable structures with interaction energies of −&#xa0;0.49 and − 0.21&#xa0;eV (TN1 and TN2, respectively), in the gas phase. The study of the absorption of natural dyes Acacetin and Juglone on these surfaces also showed that Juglone acted as a stronger chemisorption agent, with its interaction energy (E<sub>int</sub>) being as low as −&#xa0;0.27&#xa0;eV and − 0.19&#xa0;eV a significant charge transfer (~ 291, and 267 |me|) occurred, resulting in a significant reduction of the band gap by 23.29% and 44.57% in the TN1J1 and TN2J1 complexes, respectively. Density of states analysis confirmed the presence of new frontier orbitals, contributing to the improved of electronic conductivity. The optical absorption spectra also showed a shift towards longer wavelengths and an increase in absorption intensity for the dye-TiO₂ complexes, especially the Juglone-containing structures (TN2J1) with an absorption intensity of 0.1023, which improved the visible light harvesting ability. Overall, the results demonstrate the remarkable effect of functionalizing TiO₂ with Naphthoquinone-based natural dyes and introduce Juglone as a promising sensitizer. It improves efficiency and stability of dye-sensitized solar cells by enhancing the photophysical and electronic mechanisms.</p>

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Refining dye-sensitized solar cells: molecular insights into organic dye adsorption and band gap engineering on TiO₂ substrates

  • 期刊论文

  • 发表日期：

    2026年1月30日

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  • Vahdat Rafee,
  • Alireza Razeghizadeh,
  • Nahid Rashidi,
  • Saeedeh Kamalinahad

摘要

The present study investigates how organic pigments adhere to the TiO₂ surface, which acts as a mesoporous film in dye-sensitized solar cells (DSSCs). The effect of this adhesion on the electronic band gap is of interest. In this regard, eight different density functionals were evaluated to identify the most appropriate computational method to accurately describe the electronic and optical properties of TiO₂ nanoparticles. The results obtained for the absorption maximum (λmax) and band gap energy (Eg) were compared with valid experimental data and it was found that the LSDA functional provides results closely matching benchmark values. Then, geometric optimization and time-dependent density functional theory (TD-DFT) calculations were performed on the adsorption of Naphthoquinone on TiO₂. These calculations identified two stable structures with interaction energies of − 0.49 and − 0.21 eV (TN1 and TN2, respectively), in the gas phase. The study of the absorption of natural dyes Acacetin and Juglone on these surfaces also showed that Juglone acted as a stronger chemisorption agent, with its interaction energy (Eint) being as low as − 0.27 eV and − 0.19 eV a significant charge transfer (~ 291, and 267 |me|) occurred, resulting in a significant reduction of the band gap by 23.29% and 44.57% in the TN1J1 and TN2J1 complexes, respectively. Density of states analysis confirmed the presence of new frontier orbitals, contributing to the improved of electronic conductivity. The optical absorption spectra also showed a shift towards longer wavelengths and an increase in absorption intensity for the dye-TiO₂ complexes, especially the Juglone-containing structures (TN2J1) with an absorption intensity of 0.1023, which improved the visible light harvesting ability. Overall, the results demonstrate the remarkable effect of functionalizing TiO₂ with Naphthoquinone-based natural dyes and introduce Juglone as a promising sensitizer. It improves efficiency and stability of dye-sensitized solar cells by enhancing the photophysical and electronic mechanisms.