Investigation of Trion Emission in CdSe/CdSeS Core/Crown Nanoplatelets

Quasi-two-dimensional CdSe nanoplatelets (NPLs) exhibit promising potential for optoelectronic device applications due to their unique optical properties, particularly trion emission. However, the origin of the trion emission in CdSe NPLs remains unclear. In this study, the steady-state optical properties of CdSe NPLs with different CdSeS crown widths have been investigated. At low temperature, the trion emission intensity decreases with the increase of the CdSeS crown width. Using n-butylamine to remove cadmium oleate from NPLs, it is confirmed that holes in CdSe NPLs are captured by cadmium vacancies, leading to a charge imbalance and trion emission. At room temperature, thermal energy (26 meV) facilitates the escape of holes, eliminating the trion emission and shortening the fluorescence lifetime with the increase in CdSeS crown width. This work clarifies the origin of trion emission in CdSe NPLs and offers insights into the design of optoelectronic devices based on trion emission.