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Conjugated oligoelectrolytes (COEs) with phenylenevinylene (PV) repeat units are known to spontaneously intercalate into cell membranes. Twelve COEs, including seven structures reported here for the first time, were investigated for the relationship between their membrane disrupting properties and structural modifications, including the length of the PV backbone and the presence of either a tetraalkylammonium or a pyridinium ionic pendant group. Optical characteristics and interactions with cell membranes were determined using UV-Vis absorption and photoluminescence spectroscopies, and confocal microscopy. Toxicity tests on representative Gram-positive (Enterococcus faecalis) and Gram-negative (Escherichia coli) bacteria reveal generally greater toxicity to E. faecalis than to E. coli and indicate that shorter molecules have superior antimicrobial activity. Increased antimicrobial potency was observed in three-ring COEs appended with pyridinium ionic groups but not with COEs with four or five PV repeat units. Studies with mutants having cell envelope modifications indicate a possible charge based interaction with pyridinium-appended compounds. Fluorine substitutions on COE backbones result in structures that are less toxic to E. coli, while the addition of benzothiadiazole to COE backbones has no effect on increasing antimicrobial function. A weakly membrane-intercalating COE with only two PV repeat units allowed us to determine the synthetic limitations as a result of competition between solubility in aqueous media and association with cell membranes. We describe, for the first time, the most membrane disrupting structure achievable within two homologous series of COEs and that around a critical three-ring backbone length, structural modifications have the most effect on antimicrobial activity.

Metal halide perovskites (MHPs) have become a widely studied class of semiconductors for various optoelectronic devices. The possibility to tune their bandgap (Eg) over a broad spectral range from 1.2 eV to 3 eV by compositional engineering makes them particularly attractive for light emitting devices and multi‐junction solar cells. In this metadata study, data from Peer‐reviewed publications available in the Perovskite Database (www.perovskitedatabase.com) is used to evaluate the current state of Eg tuning in wideEg MHP semiconductors. Recent literature on wide Eg MHP semiconductors is examined and the data is extracted and uploaded onto the Perovskite Database. Beyond describing recent highlights and scientific breakthroughs, general trends are drawn from 45,000 individual experimental datasets of MHP solar cell devices. The historical evolution of MHP solar cells is recapitulated, and general conclusions are drawn about the current limits of device performance. Three dominant causes are identified and discussed for the degradation of performance relative to the Shockley‐Queisser (SQ) model's theoretical limit for single‐junction solar cells: 1) energetically mismatched selective transport materials for wide Eg MHPs, 2) lower optoelectronic quality of wide Eg MHP absorbers, and 3) dynamically evolving compositional heterogeneity due to light‐induced phase segregation phenomena. [ABSTRACT FROM AUTHOR]

Photo‐ and charge‐carrier‐induced ion migration is a major challenge when utilizing metal halide perovskite semiconductors for optoelectronic applications. For mixed iodide/bromide perovskites, the compositional instability due to light‐ or electrical bias induced phase‐segregation restricts the exploitation of the entire bandgap range. Previous experimental and theoretical work suggests that excited states or charge carriers trigger the process, but the exact mechanism is still under debate. To identify the mechanism and cause of light‐induced phase‐segregation phenomena, the full compositional range of methylammonium lead bromide/iodide samples are investigated, MAPb(BrxI1‐x)3 with x = 0...1, by simultaneous in situ X‐ray diffraction (XRD) and photoluminescence (PL) spectroscopy during illumination. The quantitative comparison of composition‐dependent in situ XRD and PL shows that at excitation densities of 1 sun, only the initial stage of photo‐segregation is rationalized with the previously established thermodynamic models. However, a progression of the phase segregation is observed that is rationalized by considering long‐lived accumulative photo‐induced material alterations. It is suggested that (additional) photo‐induced defects, possibly halide vacancies and interstitials, need to be considered to fully rationalize light‐induced phase segregation and anticipate the findings to provide crucial insight for the development of more sophisticated models. [ABSTRACT FROM AUTHOR]

Metal halide perovskites have received great attention in recent years, predominantly due to the high performance of perovskite solar cells. The versatility of the material, which allows the tunability of the bandgap, has led to its use in light‐emitting diodes, photo, and X‐ray detectors, among other optoelectronic device applications. Specifically in photodetectors, the tunability of the bandgap allows fabrication of spectrally selective devices. Utilizing a combinatorial inkjet printing approach, multiple perovskite compositions absorbing at specific wavelengths in a single printing step are fabricated. The drop‐on‐demand capabilities of inkjet printing enable the deposition of inks in a precise ratio to produce specific perovskite compositions in the printed thin film. By controlling the halide ratio in the compositions, a mixed halide gradient ranging from pure MAPbI3 via MAPbBr3 to MAPbCl3 is produced. The tunability in the absorption onset from 410 to 790 nm is demonstrated, covering the whole visible spectrum, with a precision of 8 nm steps for MAPb(BrxCl1−x)3 compositions. From this range of mixed halide perovskites, photodetectors which show spectral selectivity corresponding to the measured absorption onset are demonstrated, paving the way for use in a printed visible light spectrometer without the need for a dispersion element. [ABSTRACT FROM AUTHOR]

Irradiation-induced phase segregation in mixed methylammonium halide perovskite samples such as methylammonium lead bromide-iodide, MAPb(I x Br 1- x ) 3 , is being studied intensively because it limits the efficiency of wide band gap perovskite solar cells. It has been postulated that this phenomenon depends on the intrinsic ionic (in)homogeneity in samples already induced during film formation. A deeper understanding of the MAPb(I x Br 1- x ) 3 formation processes and the influence of the halide ratio, solvents, and the perovskite precursor composition as well as the influence of processing parameters during deposition, e.g., spin coating and annealing parameters, is still lacking. Here, we use a fiber optic-based optical in-situ setup to study the formation processes of the MAPb(I x Br 1- x ) 3 series on a subsecond time scale during spin coating and thermal annealing. In-situ UV-vis measurements during spin coating reveal the influence of different halide ratios, x , in the precursor solution on the preferential crystallization of the phase. Pure bromide samples directly form a perovskite phase, samples with high iodide content form a solvate intermediate phase, and samples with a mixed stoichiometry between 0.1 ≤ x ≤ 0.6 form both. This leads to a heterogeneous formation process via two competing reaction pathways, that leads to a heterogeneous mixture of phases, during spin coating and rationalizes the compositional heterogeneity of mixed bromide-iodide samples even after annealing.