Controlled Growth of Monocrystalline Organo-Lead Halide Perovskite and Its Application in Photonic Devices.

Organo-lead halide perovskites (OHPs) have recently emerged as a new class of exceptional optoelectronic materials, which may find use in many applications, including solar cells, light emitting diodes, and photodetectors. More complex applications, such as lasers and electro-optic modulators, require the use of monocrystalline perovskite materials to reach their ultimate performance levels. Conventional methods for forming single crystals of OHPs like methylammonium lead bromide (MAPbBr ) afford limited control over the product morphology, rendering the assembly of defined microcavity nanostructures difficult.

On reverse Monte Carlo constraints and model reproduction.

Reverse Monte Carlo (RMC) simulations were performed to investigate the effectiveness of any combination of five experimentally motivated constraints on the reproduction of a test case, a ternary ab initio model. It was found that low energy structures fitting a variety of constraints commonly used in the RMC methodology could still provide an incorrect description of the chemical structural unit populations in multi-elemental systems. It is shown that the use of an elemental bond type constraint is an effective way to avoid this.

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity.

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail.

Binding and Packing in Two-Component Colloidal Quantum Dot Ligand Shells: Linear versus Branched Carboxylates.

In this work, we present a combined experimental and theoretical analysis of two-component ligand shells passivating CdSe quantum dots. Using nuclear magnetic resonance spectroscopy, we first show that exposing oleate-capped quantum dots to primary carboxylic acids results in a one-for-one exchange that preserves the overall ligand surface concentration. Exposure to straight-chain acids leads to a binary ligand shell that behaves as an ideal mixture and that has a composition matching the overall acid composition of the dispersion.

Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals.

A variety of deposition methods for two-dimensional crystals have been demonstrated; however, their wafer-scale deposition remains a challenge. Here we introduce a technique for depositing and patterning of wafer-scale two-dimensional metal chalcogenide compounds by transforming the native interfacial metal oxide layer of low melting point metal precursors (group III and IV) in liquid form. In an oxygen-containing atmosphere, these metals establish an atomically thin oxide layer in a self-limiting reaction.