Exciton fine structure in CdSe nanoplatelets using a quasi-two-dimensional screened configuration-interaction framework

We compute exciton binding energies and fine-structure splittings in CdSe nanoplatelets with two zincblende geometries and one wurtzite geometry, finding that the wurtzite structure exhibits the largest bright-bright splitting due to its intrinsic in-plane anisotropy, while the zincblende structures show smaller but finite splittings arising from atomistic symmetry breaking at edges and corners. These results are obtained using a theoretical framework that we developed, which combines DFT single-particle states with screened configuration interaction, a quasi-2D dielectric screening model, and an efficient Coulomb-cutoff scheme that eliminates periodic-image interactions and enables accurate Coulomb and exchange integrals at low computational cost. This methodology provides a transferable and practical route for studying excitons in CdSe nanoplatelets and other quasi-two-dimensional nanomaterials.