No abstract

The existence of a defective area composed of nanocrystals and amorphous phases on a perovskite film inevitably causes nonradiative charge recombination and structural degradation in perovskite photovoltaics. In this study, a stoichiometric etching strategy for the top surface of a defective cesium lead halide perovskite is developed by using ionic liquids. The dissolution of the original defective area substantially exposes the underlying perovskite, which is a high‐quality surface with retained stoichiometry and lattice continuity. The ionic liquid molecules are adsorbed on the perovskite surface via Coulombic interactions and passivate the undercoordinated surface lead centers. Such a structural modulation considerably reduces the trap density of the perovskite devices and enables a record power conversion efficiency of 17.51% and an open‐circuit voltage of 1.37 V of the CsPbI2Br cell with a perovskite bandgap of 1.88 eV. This work provides a novel technical route to improve the efficiency and environmental resilience of perovskite‐based optoelectronic devices.

Using a concise synthetic strategy, a series of novel ladder-type BN-embedded heteroacenes were successfully synthesized. Their molecular skeletons render the versatile modification which is desirable for achieving unique physical properties. Organic light-emitting diode devices based on BN-embedded heteroacenes were subsequently fabricated, demonstrating their promising application as blue emitters.

No abstract

A machine learning (ML)-based multifunctional optical spectrum analysis technique is proposed to perform not only the conventional analysis functions but also the extended analysis functions, including center wavelength detection, optical signal-to-noise (OSNR) calculation, bandwidth recognition, as well as spectral distortion diagnosis. We have investigated four widely used ML algorithms, including support vector machine (SVM), artificial neural network, k-nearest neighbors, and decision tree. First, the wavelengths, OSNRs, and bandwidths of optical signals are processed by four ML methods based on the spectral data. The good performance and fast processing speed are obtained, especially for SVM, achieving the optimal accuracy (100%) and the least test time. For the need of the practical application, we also investigate the more complicated case, where wavelength, OSNR, and bandwidth are variable simultaneously so that the ML should analyze these three parameters comprehensively. Even in this case, the overall accuracy is still larger than 99.1%. In addition, the extended analysis functions are also studied to diagnose the spectral distortion caused by the cascaded filtering effect and off-center filtering effect. The number of cascaded filters and the offsets of filter shift and laser drift can be effectively estimated by the SVM with high average accuracy and low standard deviation, which are useful for failure detection and distortion recovery. This technique has the potential to be applied in the optical spectrum analyzer to implement the multifunctional spectrum analysis or in the optical performance monitor to execute the spectral distortion diagnosis.

Tuning the electron transport at the molecular scale is a key step in realizing functional electronic components for molecular electronics, and ongoing interest aims at achieving a higher modulation ratio for single‐molecular transistors. Here, a feasible strategy that connects the redox‐active moieties with conjugated chains is proposed to improve the electrochemical gating efficiency of molecular junctions in ionic liquid. Benefiting from the low energy barrier height between the Fermi level of the electrode and the frontier molecular orbitals, the conductance of C=C−Fc−Py is about one order of magnitude larger and the conductance on/off ratio shows 160 % improvement compared to that of C−C−Fc−Py at the equilibrium potential of Fc+/Fc. This work provides a new way to design high‐performance molecular devices.

The preparation of millimeter-sized poly(acrylamide-co-acrylic acid) hydrogel beads via inverse Pickering emulsion polymerization using starch-based nanoparticles (SNPs) as stabilizers is reported. Amphiphilic starch is fabricated by the introduction of butyl glycidyl ether groups and palmitate groups, and the hydrophobically modified SNPs are fabricated by a nanoprecipitation process. The obtained SNPs could adsorb at oil-water interfaces to stabilize an inverse Pickering emulsion, and the effects of oil/water volume fraction ratio and SNP concentration on emulsions are comprehensively studied. Poly(acrylamide-co-acrylic acid) hydrogel beads with a size of approximately 1 mm are obtained by inverse Pickering emulsion polymerization stabilized by SNPs. The morphology and structure of hydrogel beads are extensively investigated, which confirms that SNPs locate on the surface of hydrogel beads and act as emulsifiers and network structures present inside the beads. Polymerization is also detected to investigate the potential formation mechanism of hydrogel beads. The pHresponsive property of hydrogel beads and its potential application for drug delivery are also explored.emulsifier, formation mechanism, hydrogel beads, inverse Pickering polymerization, starchbased nanoparticles

a,x-Triethoxysilane terminated poly(dimethyl siloxane) (PDMS) oligomer, a,x-triethoxysilane terminated perfluoropolyether (PFPE) oligomer, and acrylic polyols were first synthesized via an addition reaction and free-radical polymerization. Then, crosslinked network coatings based on PFPE/PDMS/acrylic polyols for marine fouling-release applications were prepared by a condensation reaction. The structure of the crosslinked network coating was characterized by Fourier transform infrared spectroscopy. The chemical composition of the coating surface was characterized by X-ray photoelectron spectroscopy. The thermal properties, surface energy, mechanical properties, adhesion, and antiseawater immersion performance of the coatings were systematically studied. The antibiofouling properties of the crosslinked network coating were evaluated by laboratory biofouling assays with the bacteria Escherichia coli and the fouling diatom Navicula. The results from the preliminary study suggested that this crosslinked network coating had good adhesion and promising antifouling properties that were comparable to a silicone standard.