Unraveling the Growth Mechanism of Strongly Confined CsPbBr3 Perovskite Quantum Dots under Thermodynamic Equilibrium Control

Size-confined lead-halide perovskite quantum dots (PQDs) are promising materials for optoelectronic devices. Large quantities of PQDs with high ensemble uniformity are often needed for device fabrication. The thermodynamic-equilibrium-controlled synthesis can produce PQDs with good size and shape uniformity. Unfortunately, scaling up this synthesis often produces unwanted perovskite nanoplatelets (NPLs). To date, the PQD and NPL growth mechanism under thermodynamic equilibrium control remains unexplored. We discovered that the growth of size-confined CsPbBr3 PQDs is mediated by ultrasmall (∼2.4 nm) metastable nanoclusters. These nanoclusters can eventually grow into PQDs when sufficient Cs-precursors are provided. Otherwise, the unreacted nanoclusters will self-assemble and fuse into NPLs during the synthesis and/or PQD purification. By controlling the homogeneous growth of nanoclusters, strongly confined (≤5 nm) PQDs with high size uniformity can be produced at the gram scale.