Defective Nature of CdSe Quantum Dots Embedded in Inorganic Matrices

Quantum dots (QDs) embedded in inorganic
matrices have been extensively
studied for their potential applications in lighting, displays, and
solar cells. While a significant amount of research studies focused
on their experimental fabrication, the origin of their relatively
low photoluminescence quantum yield has not been investigated yet,
although it severely hinders practical applications. In this study,
we use time-dependent density functional theory (TDDFT) to pinpoint
the nature of excited states of CdSe QDs embedded in various inorganic
matrices. The formation of undercoordinated Se atoms and nonbridging
oxygen atoms at the QD/glass interface is responsible for the localization
of a hole wave function, leading to the formation of low-energy excited
states with weak oscillator strength. These states provide pathways
for nonradiative processes and compete with radiative emission. The
photoluminescence performance is predicted for CdSe QDs in different
matrices and validated by experiments. The results of this study have
significant implications for understanding the underlying photophysics
of CdSe QDs embedded in inorganic matrices that would facilitate the
fabrication of highly luminescent glasses.