Controlled Electrochemical Intercalation of Graphene/h-BN van der Waals Heterostructures.

Electrochemical intercalation is a powerful method for tuning the electronic properties of layered solids. In this work, we report an electrochemical strategy to controllably intercalate lithium ions into a series of van der Waals (vdW) heterostructures built by sandwiching graphene between hexagonal boron nitride (h-BN). We demonstrate that encapsulating graphene with h-BN eliminates parasitic surface side reactions while simultaneously creating a new heterointerface that permits intercalation between the atomically thin layers.

Single-crystal-to-single-crystal intercalation of a low-bandgap superatomic crystal.

The controlled introduction of impurities into the crystal lattice of solid-state compounds is a cornerstone of materials science. Intercalation, the insertion of guest atoms, ions or molecules between the atomic layers of a host structure, can produce novel electronic, magnetic and optical properties in many materials. Here we describe an intercalation compound in which the host [CoTe(PPr)][C], formed from the binary assembly of atomically precise molecular clusters, is a superatomic analogue of traditional layered atomic compounds.

Phonon Speed, Not Scattering, Differentiates Thermal Transport in Lead Halide Perovskites.

Thermal management plays a critical role in the design of solid state materials for energy conversion. Lead halide perovskites have emerged as promising candidates for photovoltaic, thermoelectric, and optoelectronic applications, but their thermal properties are still poorly understood. Here, we report on the thermal conductivity, elastic modulus, and sound speed of a series of lead halide perovskites MAPbX (X = Cl, Br, I), CsPbBr, and FAPbBr (MA = methylammonium, FA = formamidinium).

Unbalanced Hole and Electron Diffusion in Lead Bromide Perovskites.

We use scanning photocurrent microscopy and time-resolved microwave conductivity to measure the diffusion of holes and electrons in a series of lead bromide perovskite single crystals, APbBr, with A = methylammonium (MA), formamidinium (FA), and Cs. We find that the diffusion length of holes (L ∼ 10-50 μm) is on average an order of magnitude longer than that of electrons (L ∼ 1-5 μm), regardless of the A-type cation or applied bias. Furthermore, we observe a weak dependence of L across the A-cation series MA > FA > Cs.

Influence of annulene ratio on the electrochemical and spectroscopic properties of methano[10]annulene-thiophene random copolymers.

We describe a series of copolymerization studies whereby the nonbenzenoid aromatic methano[10]annulene is incorporated into three different types of random copolymers, two based on polythiophenes (from bithiophene and terthiophene monomers) and one based on poly(ethylene dioxythiophene). Copolymers where the annulene component was in the majority had optical and electrochemical behaviors reminiscent of the annulene homopolymer. In contrast, we found that the annulene influenced polymer electronics at very low feed ratios where the commercial comonomer was in the majority.