The goal of our group's research is to control and understand dynamic structural processes (such as phase transitions, self-assembly, and crystallization) in bulk and nanocrystalline inorganic materials, with the aim of enabling control over optoelectronic and other physico-chemical properties.

We often think of materials as static structures and seek to understand structure/property relationships only by looking at the structures at one point in time. However, the reality is that material structure is ever changing, from when we first synthesize it in the laboratory to when we incorporate it into a device (like a solar cell or battery) and then continually operate that device. In order to meet the increasing energy demands of our society in a sustainable way, we need to understand how structures change over time and how those structural changes impact optical and electronic properties.

As interdisciplinary scientists working in the areas of materials, physical, and inorganic chemistry, the Brumberg Group's approach to these fundamental problems is primarily motivated by the use of advanced characterization tools that allow us to gain access to important electronic and structural information.

Students in the group will learn both synthesis and spectroscopy, so that we can have precise control over the preparation of our own materials and so that students are aware of the many synthetic subtleties that can affect optoelectronic properties. This is especially important for nanocrystals (with organic ligands interfaced against an inorganic core) and other hybrid materials, where many processing steps that were previously believed to be relatively innocuous have recently been discovered to play critical roles on photophysical processes and the resulting device efficiencies.

Nanoparticle Nucleation and Growth Dynamics

Semiconductor nanocrystals feature a number of advantageous properties – such as solution processability, strong light absorption and emission, tunable band gaps, and efficient carrier transport – that make them promising candidates for optoelectronic applications. However, one of the major challenges associated with tailoring nanoparticle dynamics for ideal device performance is the mystery behind nanoparticle nucleation and growth pathways, which leads to difficulties in modulating nanoparticle structures and in associating nanoparticle structures with properties. As such, there is a pressing need to understand how to produce monodisperse NCs, finely tune NC shape, and inhibit defect formation, so that higher fidelity NCs can be produced both for fundamental optical studies and for incorporation in optoelectronic devices.

To this end, the Brumberg Group is employing in situ spectroscopy to monitor nanoparticle nucleation and growth mechanisms and determine how to optimize conditions to favor certain nanoparticle phases and morphologies, and how these correlate to improved carrier dynamics.

Phase Transitions in Low-Dimensional Inorganic Materials

Dynamic structural transitions are at the core of many challenges facing energy-related applications, ranging from the reduced performance of battery electrodes following repeated cycling to the poor environmental stability of perovskites in light, air, and humidity. In each of these examples, the inorganic lattice is the source of both a favorable electronic structure and good—yet not ideal—chemical stability.

Low-dimensional inorganic materials, in which the inorganic polyhedral connectivity is disrupted along one or more crystallographic axes, offer an ideal platform for understanding how to engineer optoelectronic materials that are stable in dynamic conditions. They offer many different phases for exploration, many of which feature distinct optoelectronic properties. However, while the properties of low-dimensional materials are relatively well understood under static, idealized conditions, there is a lack of understanding regarding how their photophysics evolve with dynamic changes to the lattice. By studying how both material structure and optoelectronic properties evolve over the course of structural transitions, we can gain insight into how to achieve materials that have both impressive photophysics and structural tolerance towards dynamic motion.