Surface Defects in Magic‐Sized (CdSe) 13 Clusters: A Combined Optical and Theoretical Approach

(CdSe) 13 magic‐sized clusters (MSCs) that consist of only 26 atoms represent an exciting class of materials at the boundary between molecules and quantum dots. At low temperatures, the characteristic photoluminescence (PL) shows signatures of the exciton bandgap emission at 3.65 eV, accompanied by a broad and redshifted emission at around 3.0 eV. Upon heating, the clusters reveal unique, energetically sharp PL features near the excitonic emission. For shedding light on the origin of these specific spectral fingerprints, density functional theory (DFT), time‐dependent DFT, and screened configuration interaction singles (SCIS) calculations are performed and compared with experimental data. The SCIS calculations identify excitonic fine structure states with strongly varying oscillator strengths, in excellent agreement with emissive states observed in time‐resolved PL experiments. Introduci…