Sequential Deposition of Diluted Aqueous SnO₂ Dispersion for Perovskite Solar Cells

Pylnev M., Nishikubo R., Ishiwari F., et al. Sequential Deposition of Diluted Aqueous SnO₂ Dispersion for Perovskite Solar Cells. Solar RRL 8, 2400415 (2024); https://doi.org/10.1002/solr.202400415.The widespread use of tin dioxide (SnO₂) thin films as electron transport layer (ETL) of perovskite solar cells (PSCs) has been facilitated by commercial SnO₂ nanocolloid dispersion. Nevertheless, challenges such as nanoparticle agglomeration have emerged, impacting film quality and interface properties critical for PSC performance. Herein, the efficacy of sequential, multistep spin-coating of repeatedly diluted SnO₂ aqueous suspension as a simple and effective approach to enhance ETL properties is explored. Through systematic experiments using dynamic light scattering, cyclic voltammetry, optical spectroscopy, and photoconductivity, it is demonstrated that the sequential deposition significantly improves the flatness and coverage of SnO₂, leading to improved electron transport and transfer from a perovskite layer. Such a synergetic effect enables to fabricate lead iodide PSC (FAPbI₃, FA: formamidinium) with a power conversion efficiency of 22.99% compared to 20.48% for the conventional 1-step SnO₂ layer. The findings underscore the potential of sequential SnO₂ deposition as a promising technique for robust SnO₂ films of photoelectric conversion devices

Photo-Responsive Hydrogen-Bonded Molecular Networks Capable of Retaining Crystalline Periodicity after Isomerization

Kasuya K., Oketani R., Matsuda S., et al. Photo-Responsive Hydrogen-Bonded Molecular Networks Capable of Retaining Crystalline Periodicity after Isomerization. Angewandte Chemie - International Edition 63, e202404700 (2024); https://doi.org/10.1002/anie.202404700.The molecular conformation, crystalline morphology, and properties of photochromic organic crystals can be controlled through photoirradiation, making them promising candidates for functional organic materials. However, photochromic porous molecular crystals with a networked framework structure are rare due to the difficulty in maintaining space that allows for photo-induced molecular motion in the crystalline state. This study describes a photo-responsive single crystal based on hydrogen-bonded (H-bonded) network of dihydrodimethylbenzo[e]pyrene derivative 4BDHP. A crystal composed of H-bonded undulate layers, 4BDHP-2, underwent photo-isomerization in the crystalline state due to loose stacking of the layers. Particularly, enantio-pure crystal (S,S)-4BDHP-2 allowed to reveal the structure of the photoisomerized crystal, in which the closed form (4BDHP) and open form (4CPD) were arranged alternately with keeping crystalline periodicity, although side reactions were also implied. The present proof-of-concept system of a photochromic framework that retains crystalline periodicity after photo-isomerization may provide new light-driven porous functional materials

Porous honeycomb self-assembled monolayers : tripodal adsorption and hidden chirality of carboxylate anchored triptycenes on Ag

S.D. and M.Z thank the Helmholtz Zentrum Berlin for the allocation of synchrotron radiation beamtime at BESSY II and financial support. The work was financially supported by the German Research Foundation (Deutsche Forschungsgemeinschaft; DFG) via grant ZH 63/39-1 (S.D. and M.Z.), EPSRC (doctoral training grant, R.O.d.l.M.), and CREST (Japan Science and Technology Agency; JST) via grant JPMJCR18I4 (T.F.) and also supported in part by “Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials” from MEXT, Japan. The authors acknowledge financial support through the Austrian Science Fund (FWF): P28051-N36.Molecules with tripodal anchoring to substrates represent a versatile platform for the fabrication of robust self-assembled monolayers (SAMs), complementing the conventional monopodal approach. In this context, we studied the adsorption of 1,8,13-tricarboxytriptycene (Trip-CA) on Ag(111), mimicked by a bilayer of silver atoms underpotentially deposited on Au. While tripodal SAMs frequently suffer from poor structural quality and inhomogeneous bonding configurations, the triptycene scaffold featuring three carboxylic acid anchoring groups yields highly crystalline SAM structures. A pronounced polymorphism is observed, with the formation of distinctly different structures depending on preparation conditions. Besides hexagonal molecular arrangements, the occurrence of a honeycomb structure is particularly intriguing as such an open structure is unusual for SAMs consisting of upright-standing molecules. Advanced spectroscopic tools reveal an equivalent bonding of all carboxylic acid anchoring groups. Notably, density functional theory calculations predict a chiral arrangement of the molecules in the honeycomb network, which, surprisingly, is not apparent in experimental scanning tunneling microscopy (STM) images. This seeming discrepancy between theory and experiment can be resolved by considering the details of the actual electronic structure of the adsorbate layer. The presented results represent an exemplary showcase for the intricacy of interpreting STM images of complex molecular films. They are also further evidence for the potential of triptycenes as basic building blocks for generating well-defined layers with unusual structural motifs.Publisher PDFPeer reviewe

3,11-Diaminodibenzo[a,j]phenazine: Synthesis, Properties, and Applications to Tröger's Base-Forming Ladder Polymerization

This is the accepted version of the following article: Izumi S., Inoue K., Nitta Y., et al. 3,11-Diaminodibenzo[a,j]phenazine: Synthesis, Properties, and Applications to Tröger's Base-Forming Ladder Polymerization. Chemistry - A European Journal 29, e202202702 (2023), which has been published in final form at https://doi.org/10.1002/chem.202202702. This article may be used for non-commercialpurposes in accordance with the Wiley Self-ArchivingPolicy. [https://authorservices.wiley.com/author-resources/Journal-Authors/licensing/self-archiving.html]A new class of diamino-substituted π-extended phenazine compound was synthesized, and its photophysical properties were investigated. The U-shaped diaminophenazine displayed photoluminescence in solution with moderate quantum yield. The diamino aromatic compound was found applicable to the poly-condensation with formaldehyde to form Tröger's base ladder polymer. The obtained microporous ladder polymer features high CO2 adsorption selectivity against N2, most likely due to the presence of basic nitrogen atoms in the phenazine rings

Rotaxanes with Dynamic Mechanical Chirality: Systematic Studies on Synthesis, Optical Resolution, Racemization, and Chiral-Prochiral Interconversion

Dynamic mechanical chirality of [2]rotaxane consisting of a Cs symmetric wheel and a C2v symmetric axle is discussed via the synthesis, optical resolution, racemization, and chiral-prochiral interconversion. This [2]rotaxane is achiral and/or prochiral when its wheel locates at the center of the axle, but becomes chiral when the wheel moves from the center of the axle. These were proved by the experiments on the optical resolution and racemization. The racemization energy of the optically resolved enantiomers was controlled by the bulkiness of the central substituents on the axle. Furthermore, the chiral-prochiral interconversion was achieved by relative positional control of the com-ponents. The present systematic studies will provide new insight into mechanically chiral interlocked compounds as well as the utility as dynamic chiral sources