Understanding Causalities in Organic Photovoltaics Device Degradation in a Machine-Learning-Driven High-Throughput Platform.

Organic solar cells (OSCs) now approach power conversion efficiencies of 20%. However, in order to enter mass markets, problems in upscaling and operational lifetime have to be solved, both concerning the connection between processing conditions and active layer morphology. Morphological studies supporting the development of structure-process-property relations are time-consuming, complex, and expensive to undergo and for which statistics, needed to assess significance, are difficult to be collected. This work demonstrates that causal relationships between processing conditions, morphology, and stability can be obtained in a high-throughput method by combining low-cost automated experiments with data-driven analysis methods. An automatic spectral modeling feeds parametrized absorption data into a feature selection technique that is combined with Gaussian process regression to quantify deterministic relationships linking morphological features and processing conditions with device functionality. The effect of the active layer thickness and the morphological order is further modeled by drift-diffusion simulations and returns valuable insight into the underlying mechanisms for improving device stability by tuning the microstructure morphology with versatile approaches. Predicting microstructural features as a function of processing parameters is decisive know-how for the large-scale production of OSCs.

Tailoring the surface properties of tobacco mosaic virions by the integration of bacterially expressed mutant coat protein.

Due to its small dimensions and high stability, tobacco mosaic virus (TMV) is used as nano-scaffold frequently. Its surface can be engineered to meet specific needs for technical, medical or materials applications. However, not all technically desirable TMV coat protein (CP) mutants can be propagated in plants successfully, if they change the efficiency of virion assembly. In order to circumvent this problem, a novel wild type (wt) CP-assisted and RNA-directed assembly procedure was designed for a recalcitrant CP mutant: Although pure hexahistidine-tagged CP cannot form particles on its own with TMV RNA in vitro, it was integrated into full-length particles if blended with wt CP in different proportions. The resulting rods formed dense monolayers with short range alignment on silicon substrates, substantially different from the largely wavy patterns obtained with wt TMV. Since they also mediated efficient ZnO deposition under mild conditions, the approach has yielded a new class of biotemplates which are amenable to the formation of nanostructured hybrid materials with adjustable texture for various applications.