Chitpakdee Chirawat, Jungsuttiwong Siriporn, Sudyoadsuk Taweesak, Promarak Vinich, Kungwan Nawee, Namuangruk Supawadee
National Nanotechnology Center (NANOTEC), National Science and Development Agency (NSTDA), Pathum Thani 12120, Thailand.
Center for Organic Electronics and Alternative Energy, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand.
Spectrochim Acta A Mol Biomol Spectrosc. 2017 Mar 5;174:7-16. doi: 10.1016/j.saa.2016.11.010. Epub 2016 Nov 12.
The effects of type and position of π-linker in carbazole-carbazole based dyes on their performance in dye-sensitized solar cells (DSSCs) were investigated by DFT and TDDFT methods. The calculated electronic energy level, electron density composition, charge injection and charge recombination properties were compared with those of the high performance CCT3A dye synthesized recently. It is found that that mixing a benzothiadizole (B) unit with two thiophene (T) units in the π-spacer can greatly shift absorption wavelength to near infrared region and enhance the light harvesting efficiency (LHE) resulting in increasing of short-circuit current density (J), whereas a thienothiophene unit does not affect those properties. However, a B should be not directly connected to the anchoring group of the dye because it brings electrolyte to the TiO surface which may increase charge recombination rate and consequently decrease open circuit voltage (V). This work shows how type and position of the π-linker affect the performance of DSSCs, and how to modulate those properties. We predicted that the designed dye derived from insertion of the B unit in between the two T units would have higher performance than CCT3A dye. The insight understanding from this study is useful for further design of higher performance dyes by molecular engineering.
采用密度泛函理论（DFT）和含时密度泛函理论（TDDFT）方法，研究了咔唑-咔唑基染料中π-连接体的类型和位置对其在染料敏化太阳能电池（DSSC）中性能的影响。将计算得到的电子能级、电子密度组成、电荷注入和电荷复合特性与最近合成的高性能CCT3A染料进行了比较。研究发现，在π-间隔基中混合一个苯并噻二唑（B）单元和两个噻吩（T）单元可以使吸收波长大幅移至近红外区域，并提高光捕获效率（LHE），从而导致短路电流密度（J）增加，而噻吩并噻吩单元不会影响这些性能。然而，B不应直接连接到染料的锚定基团上，因为它会将电解质带到TiO表面，这可能会增加电荷复合率，从而降低开路电压（V）。这项工作展示了π-连接体的类型和位置如何影响DSSC的性能，以及如何调节这些性能。我们预测，通过在两个T单元之间插入B单元而设计的染料将具有比CCT3A染料更高的性能。这项研究的深入理解有助于通过分子工程进一步设计高性能染料。
