Migration dynamics of excitons/biexcitons induced by a funnel-like nonuniform compression strain over organic polymers

Abstract

As a promising strategy, strain engineering has been employed on different semiconductor materials, aiming to modulate their photoelectric properties, thus innovate device applications. An interesting experimental result is the directional exciton migration induced by creating some local nonuniform strains in materials, such as “exciton funneling.” In this Letter, to clarify the dynamical mechanism and the impacting factors, we theoretically investigate the migration dynamics of excitons/biexcitons along organic polymers induced by a funnel-like nonuniform compression strain. First, the migration dynamics of an exciton/biexciton are separately demonstrated right after the strain created. It is found that both of them will migrate toward the strain center with the speeds up to 7–10 nm/ps, comparable with the experimental observations in a bending ZnO microwire, where the difference between the exciton and biexciton migration dynamics is also emphasized. We attribute the present exciton/biexciton migration mechanism to the strain-induced gradient of the exciton/biexciton creation energy along polymers. Furthermore, some typical factors impacting the exciton migration dynamics are considered, such as the strain gradient, the initial ratio of the exciton located in the strain region, the electron-lattice interaction, etc. Finally, based on these findings, we briefly discuss the possible results about the strain-modulated luminescence of organic polymers.