Morphological stability is crucially important for the long‐term stability of polymer solar cells (PSCs). Many high‐efficiency PSCs suffer from metastable morphology, resulting in severe device degradation. Here, a series of copolymers is developed by manipulating the content of chlorinated benzodithiophene‐4,8‐dione (T1‐Cl) via a random copolymerization approach. It is found that all the copolymers can self‐assemble into a fibril nanostructure in films. By altering the T1‐Cl content, the polymer crystallinity and fibril width can be effectively controlled. When blended with several nonfullerene acceptors, such as TTPTT‐4F, O‐INIC3, EH‐INIC3, and Y6, the optimized fibril interpenetrating morphology can not only favor charge transport, but also inhibit the unfavorable molecular diffusion and aggregation in active layers, leading to excellent morphological stability. The work demonstrates the importance of optimization of fibril network morphology in realizing high‐efficiency and ambient‐stable PSCs, and also provides new insights into the effect of chemical structure on the fibril network morphology and photovoltaic performance of PSCs.

Photo‐induced force microscopy (PiFM) is a new‐frontier technique that combines the advantages of atomic force microscopy with infrared spectroscopy and allows for the simultaneous acquisition of 3D topographic data with molecular chemical information at high spatial (~ 5 nm) and spectral (~ 1 cm−1) resolution at the nanoscale. This non‐destructive technique is time efficient as it requires only conventional mirror‐polishing and has fast mapping rates on the order of a few minutes that allow the study of dynamic processes via time series. Here, we review the method’s historical development, working principle, data acquisition, and evaluation, and provide a comparison with traditional geochemical methods. We review PiFM studies in the areas of materials science, chemistry and biology. In addition, we provide the first applications for geochemical samples including the visualization of faint growth zonation in zircons, the identification of fluid speciation in high‐pressure experimental samples, and of nanoscale organic phases in biominerals. We demonstrate that PiFM analysis is a time‐ and cost‐efficient technique combining high‐resolution surface imaging with molecular chemical information at the nanoscale and, thus, complements and expands traditional geochemical methods.

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Biominerals, such as nacreous bivalve shells, are important archives of environmental information. Most marine calcifiers form their shells from amorphous calcium carbonate, hypothesised to occur via particle attachment and stepwise crystallisation of metastable precursor phases. However, the mechanism of this transformation, including the incorporation of trace elements used for environmental reconstructions, are poorly constrained. Here, using shells of the Mediterranean mussel, we explore the formation of nacre from the meso- to the atomic scale. We use a combination of strontium pulse-chase labelling experiments in aquaculture and correlated micro- to sub-nanoscale analysis to show that nacre grows in a dynamic two-step process with extensional and space-filling growth components. Furthermore, we show that nacre crystallizes via localised dissolution and reprecipitation within nanogranules. Our findings elucidate how stepwise crystallization pathways affect trace element incorporation in natural biominerals, while preserving their intricate hierarchical ultrastructure.

Infrared photo-induced force microscopy (IR PiFM) was applied for imaging ultrathin sections of Norway spruce (Picea abies) at 800–1885 cm−1 with varying scanning steps from 0.6 to 30 nm. Cell wall sublayers were visualized in the low-resolution mode based on differences in their chemical composition. The spectra from the individual sublayers demonstrated differences in the orientation of cellulose elementary fibrils (EFs) and in the content and structure of lignin. The high-resolution images revealed 5–20 nm wide lignin-free areas in the S1 layer. Full spectra collected from a non-lignified spot and at a short distance apart from it verified an abrupt change in the lignin content and the presence of tangentially oriented EFs. Line scans across the lignin-free areas corresponded to a spatial resolution of ≤ 5 nm. The ability of IR PiFM to resolve structures based on their chemical composition differentiates it from transmission electron microscopy that can reach a similar spatial resolution in imaging ultrathin wood sections. In comparison with Raman imaging, IR PiFM can acquire chemical images with ≥ 50 times higher spatial resolution. IR PiFM is also a surface-sensitive technique that is important for reaching the high spatial resolution in anisotropic samples like the cell wall. All these features make IR PiFM a highly promising technique for analyzing the recalcitrant nature of lignocellulosic biomass for its conversion into various materials and chemicals. Graphic abstract