Spatially Correlated Flickering of All-inorganic Perovskite Microcrystals

All-inorganic halide perovskites, especially CsPbBr3 microcrystals, 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 behaviour can be observed in all-inorganic halide perovskites of comparable dimensions. Intriguingly, we witnessed multi-level 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 suggests that the flickering dynamics is strongly influenced by excitation power, excitation energy, and local environmental constituents. Under dry argon environment, a sharp reduction in the PL intensity is observed, indicating the formation of large number of nonradiative (NR) centers which quenches all the photogenerated carriers, suppressing overall emission intensity and PL flickering. The exposure of oxygen passivates these NR traps generated under argon, while humidity introduces metastable photoinduced NR traps (“special quenchers”) that govern the enhanced flickering behaviours. Our findings establish that spatiotemporally correlated intermittency is not limited to organometallic perovskites but extends to all-inorganic perovskite bulk emitters as well and provides new insights into the role of transient defects and atmospheric constituents in dictating emission stability.