Institute of Heritage Science (ISPC), National Research Council (CNR), Via Cozzi 53, 20125 Milano, Italy.
Department of Chemistry, Materials and Chemical Engineering "G. Natta", Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano, Italy.
Anal Chem. 2022 Feb 15;94(6):2966-2972. doi: 10.1021/acs.analchem.1c05011. Epub 2022 Feb 1.
The dye distribution within a photo-electrode is a key parameter in determining the performances of dye-sensitized photon-to-electron conversion devices, such as dye-sensitized solar cells (DSSCs). A traditional, depth profiling investigation by destructive means including cross-sectional sampling is unsuitable for large quality control applications in manufacturing processes. Therefore, a non-destructive monitoring of the dye depth profile is required, which is the first step toward a non-destructive evaluation of the internal degradation of the device in the field. Here, we present a conceptual demonstration of the ability to monitor the dye depth profile within the light active layer of DSSCs by non-destructive means with high chemical specificity using a recently developed non-destructive/non-invasive Raman method, micro-spatially offset Raman spectroscopy (micro-SORS). Micro-SORS is able to probe through turbid materials, providing the molecular identification of compounds located under the surface, without the need of resorting to a cross-sectional analysis. The study was performed on the photo-electrode of DSSCs. This represents the first demonstration of the micro-SORS concept in the solar cell area as well as, more generally, the application of micro-SORS to the thinnest layer to date. A sample set has been prepared with varying concentrations of the dye and the thickness of the matrix consisting of a titanium dioxide layer. The results showed that micro-SORS can unequivocally discriminate between the homogeneous and inhomogeneous dye depth profiles. Moreover, micro-SORS outcomes have been compared with the results obtained with destructive time-of-flight secondary ion mass spectrometry measurements. The results of the two techniques are in good agreement, confirming the reliability of micro-SORS analysis. Therefore, this study is expected to pave the way for establishing a wider and more effective monitoring capability in this important field.
光电管内的染料分布是决定染料敏化光子到电子转换器件（如染料敏化太阳能电池（DSSC））性能的关键参数之一。传统的破坏性深度剖析方法，包括横截面取样，不适合大规模的制造过程中的质量控制应用。因此，需要对染料深度分布进行非破坏性监测，这是对器件内部在现场降解进行非破坏性评估的第一步。在这里，我们通过最近开发的非破坏性/非侵入性拉曼方法——微空间偏移拉曼光谱（micro-SORS），展示了通过非破坏性手段以高化学特异性监测 DSSC 光活性层内染料深度分布的能力。micro-SORS 能够穿透混浊材料，在无需进行横截面分析的情况下，对位于表面下的化合物进行分子识别。该研究在 DSSC 的光电管上进行。这代表了 micro-SORS 概念在太阳能电池领域的首次应用，更广泛地说，micro-SORS 迄今为止首次应用于最薄的层。已经制备了一组具有不同染料浓度和由二氧化钛层组成的基质厚度的样品。结果表明，micro-SORS 可以明确区分均匀和不均匀的染料深度分布。此外，还将 micro-SORS 的结果与破坏性飞行时间二次离子质谱测量的结果进行了比较。两种技术的结果非常吻合，证实了 micro-SORS 分析的可靠性。因此，这项研究有望为在这一重要领域建立更广泛和更有效的监测能力铺平道路。
