posted on 2024-02-19, 20:18authored byHye Seon Kim, Yeongcheol Kim, Seongwoo Cho, Sohee Jeong, Sung Nam Lim, Jung Hoon Song, Yongho Choa, Seunghyun Lee, Kyoungwon Park, Weon-Sik Chae, Ju Young Woo
Reaction
crude solutions of colloidal semiconductor nanocrystal
quantum dots (QDs) contain various impurities. To use QDs in optoelectronic
devices or store them, the impurities must be removed through purification
procedures. However, the purification steps often result in the creation
of electronic traps because surface ligands are partially removed
during purifications. Hence, maintaining the original quality of the
QDs after purification is very challenging. Herein, we present a strategy
to preserve the original quality of InP/ZnSe/ZnS QDs by engineering
the charge carrier wavefunctions. By introducing a thick ZnS shell
layer, we effectively confine the charge carrier wavefunctions inside
the InP/ZnSe/ZnS QDs because the thick ZnS layer acts as a large electronic
barrier. Consequently, we obtain high-quality InP/ZnSe/ZnS QDs with
a suppressed photoluminescence quantum yield (PL QY) drop, whereas
InP/ZnSe/ZnS QDs with thin ZnS shell layers experience a considerable
decrease in their PL QY after multiple purification steps. Time-resolved
photoluminescence and single dot spectroscopy studies demonstrate
that InP/ZnSe/ZnS QDs with a properly thick ZnS shell are significantly
less affected by surface traps due to the reduced leakage of charge
carriers. Theoretical understanding based on wavefunction calculations
also supports this observation. Our strategy offers a promising way
to maintain the optoelectronic properties of QDs during purification
procedures, thereby enhancing their potential for various applications.