Frenkel Biexciton binding and many-body contributions to exciton line-shapes
Eric Bittner, University of Houston
Frenkel excitons are primary photoexcitations in organic semiconductors and are unequivocally responsible for their optical properties. Biexcitons, i.e bound exciton pairs, are, moreover, critical intermediates because they are ubiquitous in many relevant photophysical processes that occur in these materials, including exciton bimolecular annihilation, which dictates the exciton population dynamics. Understanding the details of biexciton correlations is, thus, crucial to achieving a step-change in how we design and use this particular class of semiconductors. In my talk I shall discuss our recent work concerning exciton/exciton scattering and biexciton binding in low-dimensional semiconductor systems.
For the former, we use an approach employing Ito calculus to calculate response functions for systems in which the background population of excitations is non-stationary, leading to increasing dephasing times. For the latter, we use an extended Hubbard approach to study Frenkel biexcitons in molecular polyenes. We find that both J and H aggregate excitons can form bound states, but with very different binding characteristics.