This project involves exploring optoelectronic properties of various organic materials and donor-acceptor composites on time scales from picoseconds to many seconds after photoexcitation, and on spatial scales from bulk films to a single-molecule level. The goal of the project is to understand physical mechanisms of charge photogeneration, transport, trapping and recombination in high-performance organic electronic materials, to explore structure-property relationships, and to understand relationships between charge and energy transfer on a molecular level and device performance. We study materials in device structures (on the macroscopic level, using time-resolved photocurrent and photoluminescence measurements) AND quantify the photophysics of the same molecules (and how it depends on the local nanoenrivonment) on the single-molecule level using single-molecule fluorescence microscopy. Although we are mainly an experimental group, we do a considerable amount of numerical simulations. Examples of these are solving a coupled system of nonlinear differential equations to model time-resolved photocurrent dynamics and performing Monte Carlo simulations of molecular blinking and bleaching in single-molecule fluorescence experiments. In addition to traditional model material systems such as acene and acene-thiophene derivatives, we are also pursuing studies of non-traditional organic materials. Examples of these include stable, sustainable pigments derived from wood-eating fungi, in collaboration with OSU Forestry.
In this project, we develop an optical tweezer trapping force measurement-based method to probe charge carrier and exciton dynamics of organic semiconductors at nanoscales, depending on the local nanoenvironment.
In this project, we quantify response of native (wild) bees to visual stimuli with various fluorescence and reflection spectra. Field studies are combined with optical characterization of bee traps and theoretical modeling.