We investigate at the theoretical (time-dependent) density functional theory level the influence of the nature of the anchoring group on the electronic and optical properties of oligothiophene dyes when adsorbed on ${\mathrm{Ti}\mathrm{O}}_2$ surface. The computed electronic structures point to a strong orbital hybridization between the dye and the substrate in the presence of the carboxylic acid and thiocarboxylic acid group, leading to a pronounced pinning effect of the lowest unoccupied molecular orbital (LUMO) level and faster electron injection. In contrast, phosphonic acid and catechol promote a weak electronic coupling between the two components and hence slower injection times. The simulated absorption spectra demonstrate that carboxylic and thiocarboxylic anchoring groups can induce a large redshift of the lowest optical transition of the dye upon adsorption due to a strong stabilization of the LUMO level triggered by the pinning effect while a small redshift prevails for phosphonic and catechol dyes. When pinning is active, the chain-size evolution of the lowest optical transition is also less sensitive to the conjugation length compared to the free dyes.

中文翻译：

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染料敏化太阳能电池中锚固基团性质对界面能级排列的影响：理论观点

我们在理论（随时间变化）的密度泛函理论水平上研究了锚定基团的性质对低聚噻吩染料吸附在电子和光学性质上的影响 ${钛\mathrm{Ø}}_2$表面。计算出的电子结构表明，在羧酸和硫代羧酸基团存在的情况下，染料与底物之间的轨道杂化很强，从而导致最低的未占据分子轨道（LUMO）水平和更快的电子注入而产生明显的钉扎效应。相反，膦酸和邻苯二酚会促进这两种组分之间的弱电子耦合，从而降低注射时间。模拟的吸收光谱表明，由于钉扎效应引起的LUMO能级的强稳定作用，羧基和硫代羧基固定基团在吸附时可诱导染料的最低光学跃迁发生大的红移，而膦酸和邻苯二酚染料普遍存在小红移。启用固定功能后，