Spatially correlated photoluminescence blinking and flickering of hybrid-halide perovskite micro-rods

Abstract

Temporally stochastic, abrupt photoluminescence (PL) intermittency (blinking) has been long recognized to be characteristic of single quantum-emitters as intensity fluctuations average out over the ensemble. While there are a few rare examples of PL blinking in spatially extended (~μm) yet quantum-confined (1 or 2-D) nanostructures, such phenomenon is in general spatiotemporally uncorrelated. However, recent investigations on organo-metal iodide perovskite nano-/micro-rods have revealed that blinking is plausible even in larger structures. Here, we report abrupt and discrete PL instability of entire individual methylammonium lead bromide (MAPbBr3) single-crystal rods of dimensions between 1 and 2 μm. Intriguingly, similar to bulk polycrystalline disks of MAPbBr3, these dimensionally unconfined micro-rods exhibit spatially-synchronous multi-level PL intermittency, on top of a slow time-varying base emission intensity. Here, we find two dominant intermittency characteristics, one of which is more abrupt (discrete) while the other is relatively gradual, designated as "blinking" and "flickering" respectively. One of the two intermittency behaviors is found to dominate in each micro-rod in the ensemble; however, both flickering and blinking have an extremely high spatial correlation of intensity fluctuations at short distances (<~1 μm). As opposed to micro rods which mostly “blink”, the tendency of spatially homogeneous intermittency is relatively less for micro rods which mostly “flicker”, especially over longer distances, as revealed by a correlation analysis used to quantify the extent of spatiotemporally concerted PL intermittency. We propose that the observed blinking and flickering behaviors owe to transient non-radiative traps; measurements on the same crystals under varied photoexcitation powers and under controlled atmospheric conditions suggest the existence of two distinct non-radiative traps with varying quenching efficiency, which leads to the observed diversity in the PL intermittency of entire MAPbBr3 crystals.