The design of π-conjugated molecules and polymers has driven the increase in efficiency of bulk heterojunction organic photovoltaic devices from <1% to over 12%. The pathways to generation of free charge carriers are still being uncovered. By focusing on blends of conjugated polymers with fullerenes, recent work has highlighted the impact of the design of donor–acceptor polymers on optoelectronic properties and phase-separated morphologies. This morphology of the active layer is largely controlled by processing conditions, such as use of processing additives. Developing a deep understanding of the impact of polymer chemistry and processing at the laboratory scale is key to translating the technology of organic photovoltaics from the research scale to large-area modules.

The growth kinetics of gold nanoparticles (NPs) during the reduction of HAuBr4 by hydrazine in the reverse micelles of oxyethylated surfactant Tergitol NP 4 was studied in situ by UV–vis spectroscopy. Kinetic mechanism includes the steps of slow, continuous nucleation and fast, autocatalytic surface growth. Both steps are under kinetic control of the precursor reduction. The rate of nucleation is limited by reaction in the droplets of the aqueous phase forming the cores of reverse micelles, and growth rate is limited by the reaction on the surface of gold NPs growing inside the micelles. The chemical mechanism of reduction of halogenated forms of gold AuX4 – by hydrazine is the same in the case of X = Cl, Br and includes the equilibria of formation and redox decomposition of the intermediate complexes AuIII(N2H4)X3 and AuI(N2H4)X. The initial form of AuX4 – (X = Cl, Br) does not affect the size of the final NPs synthesized in micellar solution of oxyethylated surfactant.

The emergence of methyl-ammonium lead halide (MAPbX3) perovskites motivates the identification of unique properties giving rise to exceptional bulk transport properties, and identifying future materials with similar properties. Here, we propose that this “defect tolerance” emerges from fundamental electronic-structure properties, including the orbital character of the conduction and valence band extrema, the charge-carrier effective masses, and the static dielectric constant. We use MaterialsProject.org searches and detailed electronic-structure calculations to demonstrate these properties in other materials than MAPbX3. This framework of materials discovery may be applied more broadly, to accelerate discovery of new semiconductors based on emerging understanding of recent successes.

A new theoretical model is proposed to describe the mechanical properties of bimodal nanocrystalline (BNC) materials. This composite model is comprised of coarse grains evenly distributed in the nanocrystalline (NC) matrix. In this study, we have studied the effect of grain size distribution on the constitutive behavior of BNC materials. During the plastic deformation, effects of nanocracks and dislocation emission from crack tips on the constitutive behavior of BNC materials are also analyzed. Numerical calculations have been carried out according to the model, and it is found that the nanocracks make a positive effect on the strain hardening, and the results show that this model can describe the enhanced strength and strain hardening of BNC materials successfully. The prediction of the bimodal Cu–Ag material is in good agreement with the experimental results.

Electronically active block polymers based on π-conjugated macromolecules have been investigated for applications where nanostructured electrodes are of prime import; however, controlling the nanoscale order of these materials has proven challenging. Here, we demonstrate that diblock copolymers that utilize a non-conjugated radical polymer moiety as the electronically active block assemble into ordered thin-film nanostructures. Specifically, the diblock copolymer polydimethylsiloxane-b-poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PDMS–PTMA) was synthesized via atom transfer radical polymerization to generate polymers with readily controlled molecular properties. Importantly, solvent annealing of the PDMS–PTMA thin films led to well-defined nanostructures with domain spacings of the order of ~30–40 nm.

Depolymerizable polymers are stimuli-responsive materials triggered to depolymerize rapidly and completely into their constituent monomers on command. Applications include triggerable vehicles for controlled release, restructurable materials, disappearing or sacrificial composites, and lithographic resists. Owing to their widespread utility, significant efforts have aimed to prepare and explore depolymerizable polymers and their corresponding triggers. This “Prospective” highlights advances since their discovery over a half-century ago, discusses methods in their preparation, and presents recent developments in triggered depolymerization. It also surveys applications that harness these polymers’ unique properties, while offering insights into research directions that may contribute to progress in this dynamic field.

A model with which to predict the effect of coplanar electrode geometry on diffraction uniformity in photorefractive polymer display devices was developed. Assumptions made in the standard use cases are no longer valid in the regions of extreme electric fields present in this type of device. Using electric-field induced second-harmonic generation through multiphoton microscopy, the physical response in regions of internal electric fields which fall outside the standard regimes of validity were probed. Adjustments to the standard model were made and the results of the new model corroborated through holographic four-wave mixing measurements.

While conventional metallic glass (MG) is usually an alloy that contains at least two types of different elements, monatomic metallic glass (MMG) in body-centered cubic metals has recently been vitrified experimentally through ultrafast quenching. In this research, MMG in Ta was vitrified by molecular dynamics simulations and used as a model system to explore the atomistic mechanism of hardening in MG under cyclic loading well below the yield point. It was found that significant structural ordering was caused during the elastic cycling without accumulating apparent plastic strain, which ultimately led to the crystallization of MG that has been long conjectured but rarely directly proved before. It was also revealed that tensile stresses were more likely to induce structural ordering and crystallization in MG than compressive stresses.