Biexcitons in lead halide perovskite nanocrystals

Lead halide perovskite nanocrystals are the subject of great interest owing to the unique photophysical properties of perovskites combined with the controllable properties. The complex structure and anharmonic nature of perovskites make theoretical study challenging, and a number of experimental observations have defied analysis. For example, recent reports of exciton-exciton interactions in perovskite nanocrystals have reported a potential antibinding behavior. However, the large variance in the size of nanocrystals, spectral drift, and thermal broadening of spectral lines render these reports controversial. Using quasiparticle-based path integral molecular dynamics within the effective mass approximation, we have studied the interplay of anharmonic lattice degrees of freedom, dielectric confinement, and electronic correlation to understand the multiparticle excitations over a range of nanoparticle sizes. These detailed molecular models are compared with simplified harmonic models.