2D CdSe/CdS Core–Shell Nanoplatelets for High-Performance Photodetectors

Atomically precise two-dimensional (2D) cadmium chalcogenide nanoplatelets (NPLs) have increased interest in optoelectronic applications. In this work, we highlight the influence of the reaction growth time on the structural and photophysical properties, carrier dynamics, and photodetection properties of NPLs. The coexistence of the wurtzite (WZ) and zinc blende (ZB) polymorphs in ∼5:3 ratio is found in CdSe/CdS core/shell (CS) NPLs from the Rietveld analysis of X-ray diffraction (XRD) patterns. The tuning of photoluminescence emission from green to red and 12 times enhancement of the decay time in CdSe/CdS CS NPLs have been achieved by increasing the growth time. Femtosecond transient absorption spectroscopic analysis reveals the increase in rise time from 500 to 900 fs, and the overall bleach recovery dynamics get slower with the growth time. In the CdSe/CdS CS NPLs-based photodetector device, the photo-to-dark current intensity ratio is ∼600 with a fast photoresponse time of ∼100 ms. The maximum photoresponsivity in the visible region is around ∼113 mA/W with a very high detectivity of ∼2.1 × 1013 Jones. Analysis reveals that these solution-processed CdSe/CdS CS NPLs-based photodetectors are promising for next-generation optoelectronic applications.