  Transient microscopy is of vital importance in understanding the dynamics of
optical excited states in optoelectronic materials, as it allows for a direct
visualization of the movement of energy carriers in space and time. Important
information on the influence of trap-states can be obtained using this
technique, typically observed as a slow-down of the energy transport as
carriers are trapped at defect sites. To date, however, studies of the
trap-state dynamics have been mostly limited to phenomenological descriptions
of the early time-dynamics. In this report, we show how long-acquisition-time
transient photoluminescence microscopy can be used to provide a detailed map of
the trap-state landscape in 2D perovskites, in particular when used in
combination with transient spectroscopy. We reveal anomalous spatial dynamics
of excitons in 2D perovskites, which cannot be explained with existing models
for trap limited exciton transport that only account for a single trap type.
Instead, using a continuous diffusion model and performing Brownian dynamics
simulations, we show that this behavior can be explained by accounting for a
distinct distribution of traps in this material. Our results highlight the
value of transient microscopy as a complementary tool to more common transient
spectroscopy techniques in the characterization of the excited state dynamics
in semiconductors.
