Colloidal II-VI nanoplatelets (NPLs) are solution-processable two-dimensional (2D) quantum dots that have vast potential in high-performance optoelectronic applications, including light-emitting diodes, sensors, and lasers. Superior properties, such as ultrapure emission, giant oscillator strength transition, and directional dipoles, have been demonstrated in these NPLs, which can improve the efficiency of light-emitting diodes and lower the threshold of lasers. In this review, we present an overview of the current progress and propose perspectives on the most well-studied II-VI NPLs that are suitable for the optoelectronic applications. We emphasize that the control of the symmetrical shell growth of NPLs is critical for the practical utilization of the advantages of NPLs in these devices.

Charge carrier dynamics essentially determines the performance of various optoelectronic applications of colloidal semiconductor nanocrystals. Among them, two-dimensional nanoplatelets provide new adjustment freedom for their unique core/crown heterostructures. Herein, we demonstrate that by fine-tuning the core size and the lateral quantum confinement, the charge carrier transfer rate from the crown to the core can be varied by one order of magnitude in CdSe/CdSeS core/alloy-crown nanoplatelets. In addition, the transfer can be affected by a carrier blocking mechanism, i.e., the filled carriers hinder further possible transfer. Furthermore, we found that the biexciton interaction is oppositely affected by quantum confinement and electron delocalization, resulting in a non-monotonic variation of the biexciton binding energy with the emission wavelength. This work provides new observations and insights into the charge carrier transfer dynamics and exciton interactions in colloidal nanoplatelets and will promote their further applications in lasing, display, sensing, etc.