Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies.
Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies.
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DOI：
10.3390/ijms17040487
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发表时间：
2016-04-01
影响因子：
5.6
通讯作者：
Müllen K
中科院分区：
文献类型：
--
作者：
El-Shishtawy RM;Elroby SA;Asiri AM;Müllen K
利用密度泛函理论（DFT）和时间相关密度泛函理论（TD-DFT）在B3LYP/6-311++G**水平上研究了对称和不对称正方形染料（SQD1-SQD4）的电子吸收光谱、基态几何和电子结构。计算出的基态几何形状揭示了这些染料中明显的共轭作用。采用6-311++G**基集的长距离校正时密度泛函Perdew， Burke and Ernzerhof （PBE, PBE1PBE (PBE0)）和Tao， Perdew, Staroverov, and Scuseria （TPSSh）交换泛函考察了光吸收特性。在光学数据和DFT基准计算的广泛比较中，发现6-311++G**基集的BEP泛函最适合描述电子吸收光谱。SQD1、SQD2、SQD3和SQD4的最低未占据分子轨道（LUMO）计算值分别为3.41、3.19、3.38和3.23 eV。这些值高于TiO2纳米粒子的LUMO能量（- 4.26 eV），表明在染料敏化太阳能电池（DSSCs）中，可能有电子从激发染料注入到TiO2的导带。此外，这些染料的芳香性计算结果与光学和几何上的数据一致，并以SQD4为最高芳香结构。基于优化后的分子几何形状、前沿轨道的相对位置和吸收最大值，我们提出这些染料是光伏DSSC器件的合适成分。
The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1–SQD4) were investigated using density functional theory (DFT) and time-dependent (TD-DFT) density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0)), and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh) with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO) were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (−4.26 eV) of the conduction band of TiO2 nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO2 in dye-sensitized solar cells (DSSCs). Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices.