Spatially Correlated Flickering of All-Inorganic Perovskite Microrods

All-inorganic halide perovskites, especially CsPbBr₃ microrods, are often considered to be optically stable and less defect-prone compared to their organometallic counterparts. Nevertheless, reports of photoluminescence (PL) blinking in bulk perovskite systems till date are restricted to organometallic halide perovskite nano-/microrods, leaving it an open question whether similar intermittency behavior can be observed in all-inorganic halide perovskites of comparable dimensions. Intriguingly, we witnessed multilevel PL fluctuations (flickering) in individual green-emitting CsPbBr₃ microrods. Wide-field PL microscopy reveals that the intensity fluctuations are nearly identical along the microrod, owing to charge carrier migration and waveguide-assisted propagation. Our measurements on single microrod suggest that the flickering dynamics is strongly influenced by excitation power, excitation energy, and local environmental constituents. Under dry argon environment, a substantial reduction in the PL intensity is observed, indicating the formation of a large number of nonradiative (NR) traps, which quenches all the photogenerated carriers, suppressing overall emission intensity and PL flickering. The exposure of oxygen and moisture passivates these NR traps along with generation of a few photo-induced supertraps. Our findings establish that spatiotemporally correlated intermittency is not limited to organometallic perovskites but extends to all-inorganic perovskite bulk emitters as well, in presence of certain atmospheric constituents.