Density functional theory characterization and design of high-performance diarylamine-fluorene dyes with different π spacers for dye-sensitized solar cells
Density functional theory characterization and design of high-performance diarylamine-fluorene dyes with different π spacers for dye-sensitized solar cells
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DOI：
10.1039/c1jm13028e
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发表时间：
2012
影响因子：
--
通讯作者：
Ji Zhang;Hai-Bin Li;Shiling Sun;Y. Geng;Yong Wu;Z. Su
中科院分区：
文献类型：
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作者：
Ji Zhang;Hai-Bin Li;Shiling Sun;Y. Geng;Yong Wu;Z. Su
为了解释有机染料1和2在染料敏化太阳能电池（DSSC）中能量转换效率的显著差异，采用密度泛函理论（DFT）和含时密度泛函理论（TDFT）计算了有机染料1和2与氧化钛结合前后的几何构型、电子结构和吸收光谱.这些使我们能够确定诸如与开路光电压（Voc）相关联的偶极矩之类的因素，并量化诸如光捕获效率、与短路光电流密度（Jsc）相关联的电子注入效率之类的参数。结果表明，与含噻唑间隔基的2相比，含噻吩间隔基的1能使吸收光谱发生红移，增强振子强度，提高电子注入驱动力，从而导致更大的Jsc，与实验数据吻合较好.至于Voc，我们的研究结果强调，除了一般强调的垂直偶极矩的染料指向从半导体表面向外，从染料到半导体的光注入电子的数量也是至关重要的，以获得高性能的染料与高Voc。在验证了量子化学方法的可靠性后，我们设计了另外四种具有不同π间隔基的染料来筛选更有效的有机染料。幸运的是，以1为参考，我们发现染料4与噻吩并噻吩间隔显示出增强的Jsc和Voc，这表明它将是一种更有效的用于DSSC的二芳胺-芴基有机染料，这将在新的有机染料的设计和合成中发挥理论指导作用。
To rationalize the marked difference in the energy conversion efficiency of dye sensitized solar cells (DSSCs) based on organic dyes 1 and 2 different only in their π spacer, density functional theory (DFT) and time-dependent DFT calculations of the geometries, electronic structures and absorption spectra of the organic dyes before and after binding to titanium oxide were carried out. These enable us to determine factors such as dipole moments associated with the open-circuit photovoltage (Voc), and to quantify parameters such as the light harvesting efficiency, the electron injection efficiency associated with the short-circuit photocurrent density (Jsc). The results reveal that compared to 2 with a thiazole spacer, 1 with a thiophene spacer could cause a red shift of the absorption spectrum, increase the oscillator strength and improve the driving force for electron injection, thus leading to the larger Jsc, in good agreement with experimental data. As for Voc, our results stress that apart from the generally emphasized vertical dipole moment of the dyes pointing outward from the semiconductor surface, the number of photoinjected electrons from the dye to the semiconductor is also crucial to obtain high performance dyes with high Voc. After justifying the reliability of the quantum-chemical methods, we designed another four dyes with different π spacers to screen more efficient organic dyes. Fortunately, taking 1 as reference, we find that dye 4 with a thienothiophene spacer displays an enhanced Jsc and Voc, indicating that it will be a more efficient diarylamine-fluorene-based organic dye used in DSSCs, which will play a theoretical guiding role in the design and synthesis of new organic dyes.