Compared with zero‐dimensional quantum dots and one‐dimensional nanorods, two‐dimensional nanoplatelets exhibit many unique optical properties. Due to strong quantum confinement in only one direction and the large lateral size, the CdSe nanoplatelets show large exciton binding energy, giant oscillator strength, narrow emission, large absorption cross‐section, and large optical gain. In this review, the development of synthesis technology of nanoplatelets is first briefly introduced. Subsequently, the optical properties of CdSe nanoplatelets and their heterostructures are reviewed, including absorption and photoluminescence, carrier dynamics, optical gain, and nonlinear properties. These optical properties are affected by size, material and structure. At last, the main applications of CdSe nanoplatelets in recent years are introduced, including light‐emitting diodes, lasers, light harvesting, photocatalysis, and sensing. image

The GaAsSb-based quantum well plays a very important role in optoelectronic devices due to its excellent wavelength tunability. When the dimension reduces, the quantum confinement effect will take place and the quantum well in nanowires will show many interesting characteristics. GaAsSb-based quantum-well nanowires are of contemporary interest. However, the properties of the quasi-type-II structure in a single quantum well nanowire have been rarely investigated. Here, we grow GaAs/GaAs_0.92Sb_0.08/GaAs coaxial single quantum-well nanowires and discussed their power-dependent and temperature-dependent photoluminescence. We find that due to the small band offset of conduction bands, both type-I like and type-II like emission exist in our nanowires. When electrons obtain enough thermal energy through collisions or surrounding environment, they will overcome the barrier and diffuse to the GaAs conduction band, which contributes to the type-II like recombination. These results show the optical property of the quasi-type-II quantum well in nanowires, which can pave the way toward future nanoscale quantum well devices.