Impacts of Dopant and Post-Synthetic Heat-Treatment on Carrier Relaxation of Cu²⁺-Doped CdSe Nanoplatelets

Doped II–VI semiconductor two-dimensional (2D) nanoplatelets (NPLs) are emergent optoelectronic materials due to one-dimensional strong quantum confinement. Here, we report the impact of Cu²⁺ dopant and post-synthetic heat treatment on structural modification and the ultrafast carrier relaxation of CdSe NPLs. Rietveld’s analysis reveals the isostructural atomic arrangements of Cu-doped CdSe NPLs, where dopant Cu atoms substitutionally replace Cd atoms. Significant photoluminescence quenching and the shortening of the decay time of CdSe NPLs are found in the presence of the Cu dopant. The influence of the dopant and post-synthetic heat treatment on the ultrafast relaxation processes and trap-mediated relaxation times is confirmed by the femtosecond transient absorption spectroscopy (fs-TAS) study because of the substitutional incorporation of Cu²⁺ ions in the CdSe lattice. These findings will pave the way to design doped semiconductor NPLs-based optoelectronic devices.