From Exciton to Tetraexciton: Final-State Doublets and 1P Addition Energies in a Weakly Confined Perovskite Quantum Dot.

Multiexciton photophysics in quantum dots remains understood mainly through the biexciton, while higher multiexcitons have remained obscured by rapid Auger decay and spectral congestion. Here we use time-resolved photoluminescence to resolve the multiexciton ladder in weakly confined 18 nm CsPbBr3 perovskite quantum dots, from the exciton through at least the tetraexciton. The exciton and biexciton emit as single transitions, whereas the triexciton and tetraexciton each appear as doublets. These doublets reveal distinct correlated final states, while the evolution from 3X to 4X exposes 1P addition energies that are not simply linearly additive. The higher multiexciton ladder therefore does not follow a rigid shell-filling sequence but evolves with exciton number through occupation-dependent many-body interactions. In this weakly confined regime, the higher manifold is best viewed as a correlated, lattice-dressed artificial atom whose internal structure becomes directly visible only at the triexciton and tetraexciton levels.