Imaging Dye Aggregation in MK-2, N3, N749, and SQ-2 dye···TiO2 Interfaces That Represent Dye-Sensitized Solar Cell Working Electrodes,ACS Applied Energy Materials

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Imaging Dye Aggregation in MK-2, N3, N749, and SQ-2 dye···TiO2 Interfaces That Represent Dye-Sensitized Solar Cell Working Electrodes
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2020-03-27 00:00:00 , DOI: 10.1021/acsaem.9b02001
Hao Chen _{1,

2} , Jacqueline M. Cole _{1,

2,

3,

4,

5} , Gavin B. G. Stenning ₃ , Angel Yanguas-Gil ₅ , Jeffrey W. Elam ₅ , Liliana Stan ₅ , Yun Gong ₁

Affiliation

Dye-sensitized solar cells (DSSCs) are a strong contender for next-generation photovoltaic technology with niche applications as solar-powered windows. The performance of a DSSC is particularly susceptible to the dye sensitizer, which is adsorbed onto the surface of a wide-band-gap semiconductor such as TiO₂, to form the working electrode. The nature by which such surfaces are sensitized stands to influence the resulting dye···TiO₂ interfacial structure and thence the operational performance of the DSSC working electrode. In particular, a nanoscopic understanding of the sensitization process would ultimately help to improve DSSC device function. In this study, atomic force microscopy (AFM) is used to image the nanoscopic formation of dye···TiO₂ interfacial structures. This employs, as case studies, four well-known DSSC dyes adsorbed onto amorphous TiO₂ substrates: two ruthenium-based dyes, N3 and the Black Dye (N749); and two organic dyes, the thiophenylcarbazole, MK-2, and the zwitterionic squaraine, SQ-2. We discover that all four dyes present some form of aggregation upon sensitization of TiO₂, whose spatial distributions show distinct nanoaggregate particle characteristics. These particle clusters of N749, N3, and MK-2 are found to assemble in lines of nanoaggregates, while clusters of SQ-2 dye chromophores distribute themselves randomly on the amorphous TiO₂ substrates. This nanoparticle structural assembly persists even when these dye···TiO₂ interfaces are fabricated using hundred-fold diluted dye sensitization concentrations. The formation of dye aggregates in N749 is further studied as a function of dye sensitization time. This tracks the pattern formation of aggregates of N749 and reveals that dye aggregation begins within the first hour and has completed within a 5 h period. The large expanse of dye nanoaggregates observed shows that dye···dye interactions are much more important than previously envisaged, while the nature of their spatial distribution can be related to different aggregation modes of the dye molecules. These nanostructural features will undoubtedly impact the performance of DSSCs.

中文翻译：

在代表染料敏化太阳能电池工作电极的MK-2，N3，N749和SQ-2染料···TiO ₂界面中成像染料聚集

染料敏化太阳能电池（DSSC）是下一代光伏技术的有力竞争者，其利基应用如太阳能窗户。DSSC的性能特别容易受到染料敏化剂的影响，该染料敏化剂被吸附到宽带隙半导体如TiO ₂的表面上以形成工作电极。这种表面被敏化的性质会影响所得的染料···TiO ₂界面结构，并因此影响DSSC工作电极的操作性能。特别地，对敏化过程的纳米理解最终将有助于改善DSSC装置的功能。在这项研究中，原子力显微镜（AFM）用于成像染料···TiO ₂的纳米形成界面结构。作为案例研究，它采用了四种吸附在无定形TiO ₂基材上的著名DSSC染料：两种钌基染料N3和黑染料（N749）；另一种是基于钌的染料。以及两种有机染料，硫代苯基咔唑MK-2和两性离子方酸SQ-2。我们发现，所有四种染料在TiO ₂敏化后均呈现某种形式的聚集，其空间分布显示出明显的纳米聚集颗粒特征。发现N749，N3和MK-2的这些粒子簇聚集在纳米聚集体的行中，而SQ-2染料生色团的簇随机地将自己分布在无定形TiO ₂基底上。即使这些染料···TiO ₂使用一百倍稀释的染料敏化浓度制造界面。进一步研究了N749中染料聚集体的形成与染料敏化时间的关系。这追踪了N749聚集体的模式形成，并揭示了染料聚集在第一个小时内开始，并在5小时内完成。观察到的大范围染料纳米聚集体表明，染料···染料相互作用比以前设想的要重要得多，而它们的空间分布性质可能与染料分子的不同聚集模式有关。这些纳米结构特征无疑将影响DSSC的性能。

更新日期：2020-03-27

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