PDF(Pubmed)
Abstract：
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.
摘要：
提高染料敏化太阳能电池的整体效率的主要挑战是提高小分子受体的光电特性。这项工作主要研究了作为受体部分掺入到新设计的一系列D-A-A染料中的腈中的共轭作用。密度泛函理论用于专门研究腈中的单双和单三共轭如何改变这些染料的光学和电子性质。具有高度共轭腈单元的Cy-4c染料获得了最小的带隙（1.80eV），甚至小于强氰丙烯酸锚定基团(2.07eV)。在腈基中缺乏共轭的染料对LUMO没有贡献，而LUMO从供体延伸到共轭腈组分，促进分子内电荷转移并导致与膜表面的强结合。态密度分析显示，共轭腈通过在LUMO中的有效贡献对染料的电子性质有相当大的影响，超过了众所周知的强2,1,3-苯并噻二唑受体单元的作用。使用时间依赖性密度泛函理论（TD-DFT）研究了激发态性质和吸收光谱。腈单元中的共轭导致吸收带变宽，加强,向近红外区域移动。所提出的染料还显示出最佳的光伏性能;所有染料具有高的光捕获效率（LHE）值，特别是染料Cy-3b和Cy-4c的96%，具有最共轭的腈部分。共轭程度较高的染料具有较长的激发寿命值，通过在界面处引起稳定的电荷复合来促进电荷转移。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了新的见解。这可能导致太阳能电池极其有效的光敏剂的发展。
