<p>Azulene-core-based hole-transporting materials (HTMs) are emerging as stable, efficient candidates for perovskite solar cells (PSCs). This study introduces five novel HTMs (AZU1-AZU5) featuring a donor-π-acceptor (D-π-A) framework, combining an azulene core with dimethoxy triphenylamine (DMTPA) and modified acceptor groups. Quantum chemical approach using density functional theory and time-dependent DFT revealed that these materials possess well-aligned HOMO energy levels (-5.25 to -5.32&#xa0;eV), reduced exciton binding energies (0.10 to 0.20&#xa0;eV), and strong absorption in the visible region (λ<sub>max</sub> ≤ 539&#xa0;nm), enhancing their suitability for hole extraction in PSCs. Compared with the reference molecule AZU-OMeTPA, the designed HTMs exhibit lower hole reorganization energies (0.2108 to 0.2316&#xa0;eV) to ensure fast and efficient hole transport. Excited-state charge transfer characteristics, such as the amount of charge transfer q<sup>CT</sup>, charge density difference, charge transfer distance (D<sub>index</sub>), hole electron overlap (S<sub>±</sub>), H-index, t-index, and others, were evaluated alongside ionization potential and electron affinity. Among the studied HTMs, AZU3 showed the highest UV absorption in both gas and solvent phases. AZU5 exhibited the deepest fitting HOMO energy level (-5.31&#xa0;eV), lowest binding energies, lowest HOMO–LUMO energy gap (1.24&#xa0;eV), and highest dipole moments. The higher q<sup>CT</sup> (0.992), total amount of charge transfer (6.58e), and intrinsic charge transfer (93.02%) make AZU5 a stronger candidate for the enhanced charge transfer character. These findings highlight the impact of acceptor modifications on tuning HTM performance, offering a strategic pathway toward designing efficient HTMs for next-generation PSCs. Nevertheless, the present work is limited to computational predictions, and future experimental investigations are necessary to confirm the simulated trends and address potential device-level influences.</p>

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Molecular Engineering of Azulene-Core Based Efficient Hole-Transport Materials for Perovskite Solar Cells Following D-π-A Motif: A DFT Study

  • Nabeel Shahzad,
  • Rida Fatima,
  • Zahra Anum Mahboob,
  • Hanane Etabti,
  • Shahzad Ali Shahid Chatha,
  • Shahid Hussain,
  • Javed Iqbal

摘要

Azulene-core-based hole-transporting materials (HTMs) are emerging as stable, efficient candidates for perovskite solar cells (PSCs). This study introduces five novel HTMs (AZU1-AZU5) featuring a donor-π-acceptor (D-π-A) framework, combining an azulene core with dimethoxy triphenylamine (DMTPA) and modified acceptor groups. Quantum chemical approach using density functional theory and time-dependent DFT revealed that these materials possess well-aligned HOMO energy levels (-5.25 to -5.32 eV), reduced exciton binding energies (0.10 to 0.20 eV), and strong absorption in the visible region (λmax ≤ 539 nm), enhancing their suitability for hole extraction in PSCs. Compared with the reference molecule AZU-OMeTPA, the designed HTMs exhibit lower hole reorganization energies (0.2108 to 0.2316 eV) to ensure fast and efficient hole transport. Excited-state charge transfer characteristics, such as the amount of charge transfer qCT, charge density difference, charge transfer distance (Dindex), hole electron overlap (S±), H-index, t-index, and others, were evaluated alongside ionization potential and electron affinity. Among the studied HTMs, AZU3 showed the highest UV absorption in both gas and solvent phases. AZU5 exhibited the deepest fitting HOMO energy level (-5.31 eV), lowest binding energies, lowest HOMO–LUMO energy gap (1.24 eV), and highest dipole moments. The higher qCT (0.992), total amount of charge transfer (6.58e), and intrinsic charge transfer (93.02%) make AZU5 a stronger candidate for the enhanced charge transfer character. These findings highlight the impact of acceptor modifications on tuning HTM performance, offering a strategic pathway toward designing efficient HTMs for next-generation PSCs. Nevertheless, the present work is limited to computational predictions, and future experimental investigations are necessary to confirm the simulated trends and address potential device-level influences.