D–A−π–A dyes differ from the traditional D−π–A framework having several merits in dye-sensitized solar cell (DSSC) applications. With regard to D−π–A dyes, D–A−π–A dyes red-shift absorption spectra and show particular photostability. Nevertheless, the effects of internal acceptor on the charge transfer (CT) probability are unclear. We employed density functional theory (DFT), time-dependent DFT (TD-DFT), and TD-DFT molecular dynamics (MD) simulations to investigate the effects of internal acceptor on the photophysical properties of D–A−π–A dyes on DSSCs. Our calculations show the absorption bands of D–A−π–A dyes with strong electron-withdrawing internal acceptors exhibiting significant characteristics of dual CT; the excited electron density is transferred to the internal and terminal acceptors simultaneously. Particularly, the internal acceptor traps a significant amount of electron density upon photoexcitation. The TD-DFT MD simulations at 300 K show that only a small amount of excited electron density is pushing and pulling between the internal acceptor and terminal acceptor moieties; the thermal energy is not high enough to drive the electron density from the internal acceptor to the terminal acceptor. Our study reveals the nature of CT bands of D–A−π–A dyes providing a theoretical basis for further rational engineering.

中文翻译：

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D–A–π–A有机增感剂中内部吸电子部分对DSSCs光物理性质的影响：计算研究

D–A–π–A染料不同于传统的D–A–π–A框架，在染料敏化太阳能电池（DSSC）应用中具有多个优点。关于D-π-A染料，D-A-π-A染料吸收了红移吸收光谱，并显示出特别的光稳定性。然而，尚不清楚内部受体对电荷转移（CT）概率的影响。我们采用密度泛函理论（DFT），时变DFT（TD-DFT）和TD-DFT分子动力学（MD）模拟来研究内部受体对D–A–π–A染料光物理性质的影响。 DSSC。我们的计算表明，具有强吸电子内受主的D–A–π–A染料的吸收带具有双重CT的显着特征；激发的电子密度同时转移到内部和末端受体上。特别，内部受光器在光激发时会捕获大量电子密度。TD-DFT MD在300 K时的模拟表明，只有少量的激发电子密度在内部受体和末端受体部分之间推拉。热能不够高，无法将电子密度从内部受体传递到末端受体。我们的研究揭示了D–A–π–A染料CT谱带的性质，为进一步合理的工程设计提供了理论基础。热能不够高，无法将电子密度从内部受体传递到末端受体。我们的研究揭示了D–A–π–A染料CT谱带的性质，为进一步合理的工程设计提供了理论基础。热能不够高，无法将电子密度从内部受体传递到末端受体。我们的研究揭示了D–A–π–A染料CT谱带的性质，为进一步合理的工程设计提供了理论基础。