Physics Department, Faculty of Science, Taibah University, Madinah 44256, Saudi Arabia.
Department of Physics, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 11623, Saudi Arabia.
Int J Mol Sci. 2024 Jun 28;25(13):7138. doi: 10.3390/ijms25137138.
A major challenge in improving the overall efficiency of dye-sensitized solar cells is improving the optoelectronic properties of small molecule acceptors. This work primarily investigated the effects of conjugation in nitriles incorporated as acceptor moieties into a newly designed series of D-A-A dyes. Density functional theory was employed to specifically study how single-double and single-triple conjugation in nitriles alters the optical and electronic properties of these dyes. The Cy-4c dye with a highly conjugated nitrile unit attained the smallest band gap (1.80 eV), even smaller than that of the strong cyanacrylic anchor group (2.07 eV). The dyes lacking conjugation in nitrile groups did not contribute to the LUMO, while LUMOs extended from donors to conjugated nitrile components, facilitating intramolecular charge transfer and causing a strong bind to the film surface. Density of state analysis revealed a considerable impact of conjugated nitrile on the electronic properties of dyes through an effective contribution in the LUMO, exceeding the role of the well-known strong 2,1,3-benzothiadiazole acceptor unit. The excited state properties and the absorption spectra were investigated using time-dependent density functional theory (TD-DFT). Conjugation in the nitrile unit caused the absorption band to broaden, strengthen, and shift toward the near-infrared region. The proposed dyes also showed optimum photovoltaic properties; all dyes possess high light-harvesting efficiency (LHE) values, specifically 96% for the dyes Cy-3b and Cy-4c, which had the most conjugated nitrile moieties. The dyes with higher degrees of conjugation had longer excitation lifetime values, which promote charge transfer by causing steady charge recombination at the interface. These findings may provide new insights into the structure of conjugated nitriles and their function as acceptor moieties in DSSCS, which may lead to the development of extremely effective photosensitizers for solar cells.
提高染料敏化太阳能电池整体效率的一个主要挑战是改善小分子受体的光电性能。这项工作主要研究了将腈作为受体部分引入一系列新设计的 D-A-A 染料中时的共轭对其光学和电子性质的影响。密度泛函理论专门用于研究腈中单键-双键和单键-三键共轭如何改变这些染料的光学和电子性质。带有高度共轭腈单元的 Cy-4c 染料获得了最小的带隙（1.80 eV），甚至比强氰基丙稀酸酯锚定基团（2.07 eV）还要小。缺乏腈基共轭的染料对 LUMO 没有贡献，而 LUMO 从供体扩展到共轭腈组成部分，促进了分子内电荷转移，并与膜表面产生强烈的结合。态密度分析表明，共轭腈通过在 LUMO 中有效贡献对染料的电子性质产生了相当大的影响，超过了著名的强 2,1,3-苯并噻二唑受体单元的作用。使用时间相关密度泛函理论（TD-DFT）研究了激发态性质和吸收光谱。腈单元的共轭导致吸收带变宽、增强并向近红外区域移动。所提出的染料还表现出最佳的光伏性能；所有染料都具有高光捕获效率（LHE）值，对于带有最多共轭腈部分的 Cy-3b 和 Cy-4c 染料，LHE 值高达 96%。具有更高共轭度的染料具有更长的激发寿命值，这通过在界面处稳定的电荷复合促进电荷转移。这些发现可能为共轭腈的结构及其在 DSSCS 中作为受体部分的功能提供新的见解，这可能导致开发出用于太阳能电池的极其有效的光敏剂。
