Research

Gaining a fundamental understanding of the quantum dynamics of energy and charge transfer is key for any scalable technology based on next-generation photovoltaic and optoelectronic materials. However, the eventual fate of excitons and charge carriers on longer timescales is also what determines carrier transport and device efficiency. Thus it becomes vital to not only answer questions of fundamental interest, such as the mechanism of energy and charge transfer on femtosecond timescales, but also to address questions of applied interest, such as tracking the eventual fate of exciton and charge carriers in a device to understand and control the loss mechanisms.

We develop advanced spectroscopy and imaging tools, and theoretical models to probe emerging materials such as organic polymers and singlet fission materials, inorganic perovskites, and layered 2D materials. We are also interested in probing natural photosynthetic proteins in order to guide the design of artificial photovoltaic materials. We strongly believe that exploring questions such as whether quantum coherences or vibronic mixing can enhance function in natural and artificial light harvesting systems can have a defining impact on the design of efficient photovoltaic materials.

Fundamental Perspective

Our group develops state-of-the-art coherent multidimensional spectroscopic techniques (click to know more about the technique) and theoretical models to understand ultrafast vibrational-electronic motions which initiate energy and charge delocalization on the nanoscale in natural and artificial light-harvesting systems. Such techniques have the ability to probe matter through controlled interactions with femtosecond pulses along multiple spectral dimensions on the sub-micron lengthscales. Recent examples can be found in under corresponding Research Verticals. Such techniques are relevant for understanding and controlling the electron-phonon couplings that delocalize energy and change. Theoretical impetus of our group is to develop toy models of energy and charge delocalization through numerically exact approaches. We use such Hamiltonians to simulate and better understand our experimental spectra.

Applied Perspective

We are very interested in applying our optical devices to devise better sensing and imaging tools. As an example, combining spectroscopy and imaging tools allows us to image carrier loss mechanisms on a device level. One can then answer extremely relevant questions such as whether grain boundaries and specific morphologies introduce carrier loss mechanisms through mid-bandgap states, whether increased polaronic character at grain boundaries assists in charge dissociation, and whether specific spin coating methods inhibit trap formation in photovoltaic thin films. 

Please go over our recent publications for a flavor of the experimental and theoretical work carried out in the group.