Discrete hopping model of exciton transport in disordered media

Abstract

A model of dispersive exciton transport has been developed for a medium with exciton energy levels randomly distributed in both space and energy scale. For a boxcar density of states of excitons an analytical solution is given describing the exciton density as a function of time and the proximity to the exciton quenching interfaces. The model parameters, such as exciton lifetime, effective number of exciton energy levels within inhomogeneously broadened density of states, and hopping distance and hopping rate constants, could be determined using time-resolved photoluminescence data. The developed model is verified via comparison with experimental data on the time-dependent photoluminescence decay of the conjugated polymer MEH-PPV and on the spectrum of internal quantum efficiency of the heterojunction photovoltaic device based on the $\mathrm{MEH}\text{−}\mathrm{PPV}∕\mathrm{Ti}{\mathrm{O}}_2$ nanostructure.