Low‐bandgap mixed tin–lead perovskite solar cells (PSCs) have been attracting increasing interest due to their appropriate bandgaps and promising application to build efficient all‐perovskite tandem cells, an effective way to break the Shockley–Queisser limit of single‐junction cells. Tin fluoride (SnF₂) has been widely used as a basis along with various strategies to improve the optoelectronic properties of low‐bandgap SnPb perovskites and efficient cells. However, fully understanding the roles of SnF₂ in both films and devices is still lacking and fundamentally desired. Here, the functions of SnF₂ in both low‐bandgap (FASnI₃)_0.6(MAPbI₃)_0.4 perovskite films and efficient devices are unveiled. SnF₂ regulates the growth mode of low‐bandgap SnPb perovskite films, leading to highly oriented topological growth and improved crystallinity. Meanwhile, SnF₂ prevents the oxidation of Sn²⁺ to Sn⁴⁺ and reduces Sn vacancies, leading to reduced background hole density and defects, and improved carrier lifetime, thus largely decreasing nonradiative recombination. Additionally, the F⁻ ion preferentially accumulates at hole transport layer/perovskite interface with high SnF₂ content, leading to more defects. This work provides in‐depth insights into the roles of SnF₂ additives in low‐bandgap SnPb films and devices, assisting in further investigations into multiple additives and approaches to obtain efficient low‐bandgap PSCs.

The extracellular matrix (ECM) is a complex, dynamic network present within all tissues and organs that not only acts as a mechanical support and anchorage point but can also direct fundamental cell behavior, function, and characteristics. Although the importance of the ECM is well established, the integration of well‐controlled ECMs into Organ‐on‐Chip (OoC) platforms remains challenging and the methods to modulate and assess ECM properties on OoCs remain underdeveloped. In this review, current state‐of‐the‐art design and assessment of in vitro ECM environments is discussed with a focus on their integration into OoCs. Among other things, synthetic and natural hydrogels, as well as polydimethylsiloxane (PDMS) used as substrates, coatings, or cell culture membranes are reviewed in terms of their ability to mimic the native ECM and their accessibility for characterization. The intricate interplay among materials, OoC architecture, and ECM characterization is critically discussed as it significantly complicates the design of ECM‐related studies, comparability between works, and reproducibility that can be achieved across research laboratories. Improving the biomimetic nature of OoCs by integrating properly considered ECMs would contribute to their further adoption as replacements for animal models, and precisely tailored ECM properties would promote the use of OoCs in mechanobiology.

Basic human functions such as breathing and digestion require mechanical stretching of cells and tissues. However, when it comes to laboratory experiments, the mechanical stretching that cells experience in the body is not often replicated, limiting the biomimetic nature of the studies and the relevance of results. Herein, we establish the importance of mechanical stretching during in vitro investigations by reviewing seminal works performed using cell-stretching platforms, highlighting important outcomes of these works as well as the engineering characteristics of the platforms used. Emphasis is placed on the compatibility of cell-stretching devices (CSDs) with live-cell imaging as well as their limitations and on the research advancements that could arise from live-cell imaging performed during cell stretching.