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Monday, August 03, 2015
3:00 PM - 4:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Colloquium

Understanding the Nature of Excitons in Organic Semiconductors from First Principles Theory

Sahar Sharifzadeh
Boston University

Design of new organic materials for efficient optoelectronics relies on understanding their excited-state electronic structure, which is significantly influenced by both chemistry and solid-state morphology. While many organic materials have varying degrees of disorder, crystalline films with long-range order provide an opportunity to understand many fundamental physical properties relevant to electronics. Here, we will present first-principles many-body perturbation theory calculations of prototypical bulk organic semiconductors, aimed at understanding the influence of solid-state structure on the nature of optical excitations (excitons). Analysis of the electron-hole correlation function, computed within the GW and Bethe-Salpeter equation approach, allows us to quantify the extent and degree of charge transfer of the solid-state exciton. For rubrene and pentacene crystals, we predict that the solid-state exciton is highly sensitive to strain and changes in inter-molecular orientation induced by functionalization. These results indicate that the nature of excitons in organic semiconductors can be controlled by tuning solid-­‐state morphology, suggesting a new strategy for the design of optoelectronic materials.

Host: Sergei Tretiak