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In time-of-flight secondary ion mass spectrometry (ToF-SIMS), multivariate analysis (MVA) methods such as principal component analysis (PCA) are routinely employed to differentiate spectra. However, additional insights can often be gained by comparing processes, where each process is characterized by its own start and end spectra, such as when identical samples undergo slightly different treatments or when slightly different samples receive the same treatment. This study proposes a strategy to compare such processes by decomposing the loading vectors associated with them, which highlights differences in the relative behavior of the peaks. This strategy identifies key information beyond what is captured by the loading vectors or the end spectra alone. While PCA is widely used, partial least-squares discriminant analysis (PLS-DA) serves as a supervised alternative and is the preferred method for deriving process-related loading vectors when classes are narrowly separated. The effectiveness of the decomposition strategy is demonstrated using artificial spectra and applied to a ToF-SIMS materials science case study on the photodegradation of N719 dye, a common dye in photovoltaics, on a mesoporous TiO2 anode. The study revealed that the photodegradation process varies over time, and the resulting fragments have been identified accordingly. The proposed methodology, applicable to both labeled (supervised) and unlabeled (unsupervised) spectral data, can be seamlessly integrated into most modern mass spectrometry data analysis workflows to automatically generate a list of peaks whose relative behavior varies between two processes, and is particularly effective in identifying subtle differences between highly similar physicochemical processes. [ABSTRACT FROM AUTHOR]

In the field of photovoltaics (PV), an important trend is to increase the aesthetic and creative design aspects of solar cells towards more attractive and customized devices for integration in for instance architecture, e.g. building integrated photovoltaics (BIPV). Here we introduce the concept of "photovoltaic photographs", defined as semi-transparent solar cells (STSC) that are treated with a light-induced process to integrate an image in the photoactive layer, allowing creative applications such as photovoltaic photographs, paintings, posters, etc. Contrary to previously reported patterning processes used in emerging photovoltaics such as inkjet printing or methods where patterned transparent foils are assembled on top of the solar cells, the approach proposed here to obtain a patterned 2D-photoactive layer, is by using a direct photo-induced patterning process based on photobleaching of chromophores. Proof-of-principle demonstrators have been realized using dye-sensitized solar cells and the obtained insights can open the way to the exploration of combining this concept with other PV technologies. [Display omitted] • Semi-transparent solar cells with high-resolution image as photo-active layer. • Alternative patterning method via photo-induced process. • Proof-of-principle demonstrators of 9 × 9 cm 2 using dye-sensitized solar cells. • The process is easy to implement, scalable, and provides novel creative applications. • This methodology can possibly be transferred to other classes of emerging PV. [ABSTRACT FROM AUTHOR]