The Wong Lab

In situ ultrafast spectroscopy of materials formation

Research

Overview

Photovoltaic and optoelectronic materials are often assembled from nanoscale building blocks, such as small organic molecules, quantum dots, or polymers. Different methods can be used to put these building blocks together, but one of the most common and cost-effective methods is deposition from a solution. As solvent evaporates, the individual building blocks get closer together, start to interact, and end up in particular physical arrangements, termed the material's 'mesostructure'. As components of a system couple together, these physical arrangement can result in disorder and defects, and the group of particles can exhibit collective phenomena which alter the behavior of excitons and carriers in unexpected ways. 

Research in our lab seeks to adapt time-resolved exciton spectroscopies to the measurement of nanoscale building blocks during their self-assembly into mesoscale architectures. We will measure the electronic structure and exciton dynamics in situ and in real-time as irreversible processes occur, such as crystallization, self-assembly and chemical bond formation. By measuring and comparing how exciton behavior changes during self-assembly using various solution deposition techniques, we will develop strategies to control self-assembly and create materials with designer excitonic properties. 

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The ultimate goal of our research is to establish the physical rules governing both the self-assembly of mesoscale structures and the emergence of collective photophysical properties during these processes. We aim to understand, predict and control the assembly of individual building blocks, and utilize the collective behavior of these mesoscale systems to provide tunable macroscopic functionality. 

Tools and Skills

We will measure electronic structure and exciton dynamics using non-linear, ultrafast spectroscopies such as transient absorption, transient grating, and 2D photon echo spectroscopy. These measurements will be performed using a femtosecond laser system, and controlled using home-built software. We will study a number of different chemical samples while they are evolving, using various methods of materials preparation and controlled degradation.

Students will gain experience in:

  • Operating and maintaining a femtosecond laser and optical amplifiers
  • Handling optics and optomechanics to build and control optical experiments
  • Writing software to control motorized components and data acquisition
  • Preparing thin-film materials using a number of different techniques
  • Working with chemicals relevant to photovoltaics and organic electronics
  • Analyzing data and designing simulations using high-level languages like Matlab