Electronic structure and optical properties of surface defects in CdS quantum dots from many-body perturbation theory

The tunability of energy levels and optical properties of CdS quantum dots (QDs) renders them an excellent choice for applications in electronics and optical devices.However, a major factor limiting their performance is the low photoluminescence, which is often attributed to defect-induced trap states.Here, we leverage first-principles density functional theory and many-body perturbation theory to establish atomistic structure-property relationships for common surface defects in CdS QDs.Our results reveal distinct in-gap defect states in the electronic structure and how they modulate the optical properties of QDs in both the wurtzite and zinc blende polymorphs.Furthermore, we discuss how these in-gap defect states, also commonly known as trap states, can be effectively removed via surface passivation.Our work provides not only benchmark data for future experiments and calculations but also insights into defect-induced properties and surface passivation schemes.