Emissive TrapsLead to Asymmetric PhotoluminescenceLine Shape in Spheroidal CsPbBr₃ Quantum Dots

The morphology of quantum dots plays an important role in governing their photophysics. Here, we explore the photoluminescence of spheroidal CsPbBr₃ quantum dots synthesized via the room-temperature trioctylphosphine oxide/PbBr₂ method. Despite photoluminescence quantum yields nearing 100%, these spheroidal quantum dots exhibit an elongated red photoluminescence tail not observed in typical cubic quantum dots synthesized via hot injection. We explore the origins of this elongated red tail through structural and optical characterization including small-angle X-ray scattering, transmission electron microscopy and time-resolved, steady-state, and single quantum dot photoluminescence. From these measurements we conclude that the red tail originates from emissive traps. We show that treating spheroidal quantum dots with phenethylammonium bromide decreases the line shape asymmetry and increases passivation–consistent with emissive traps due to polar facets.