Supramolecular Engineering for Formamidinium‐Based Layered 2D Perovskite Solar Cells: Structural Complexity and Dynamics Revealed by Solid‐State NMR Spectroscopy

Perovskite solar cells are one of the most promising photovoltaic technologies, although their molecular level design and stability toward environmental factors remain a challenge. Layered 2D Ruddlesden–Popper perovskite phases feature an organic spacer bilayer that enhances their environmental stability. Here, the concept of supramolecular engineering of 2D perovskite materials is demonstrated in the case of formamidinium (FA) containing A₂FA_n?1Pb_nI_3n+1 formulations by employing (adamantan‐1‐yl)methanammonium (A) spacers exhibiting propensity for strong Van der Waals interactions complemented by structural adaptability. The molecular design translates into desirable structural features and phases with different compositions and dimensionalities, identified uniquely at the atomic level by solid‐state NMR spectroscopy. For A₂FA₂Pb₃I₁₀, efficiencies exceeding 7% in mesoscopic device architectures without any additional treatment or use of antisolvents for ambient temperature film deposition are achieved. This performance improvement over the state‐of‐the‐art FA‐based 2D perovskites is accompanied by high operational stability under humid ambient conditions, which illustrates the utility of the approach in perovskite solar cells and sets the basis for advanced supramolecular design in the future.     

Modeling the membrane environment has implications for membrane protein structure and function: Influenza A M2 protein

The M2 protein, a proton channel, from Influenza A has been structurally characterized by X‐ray diffraction and by solution and solid‐state NMR spectroscopy in a variety of membrane mimetic environments. These structures show substantial backbone differences even though they all present a left‐handed tetrameric helical bundle for the transmembrane domain. Variations in the helix tilt influence drug binding and the chemistry of the histidine tetrad responsible for acid activation, proton selectivity and transport. Some of the major structural differences do not arise from the lack of precision, but instead can be traced to the influences of the membrane mimetic environments. The structure in lipid bilayers displays unique chemistry for the histidine tetrad, which binds two protons cooperatively to form a pair of imidazole‐imidazolium dimers. The resulting interhistidine hydrogen bonds contribute to a three orders of magnitude enhancement in tetramer stability. Integration with computation has provided detailed understanding of the functional mechanism for proton selectivity, conductance and gating of this important drug target.