Quantum Dots & Nanophosphors

Difference Between Quantum Dots (QDs) & Nanophosphors (NPs)

Both quantum dots and nanophosphors are luminescent nanocrystals made into nanozise particles. Quantum dots (QDs) are generally less than 10nm in size and they operate based on the quantum confinement effect whereby the QD bandgap and emission color are determined by the particle size. The smaller the particle size, the larger the bandgap and the higher the energy (the shorter the wavelength) of light produced by the QDs.

 

Luminescent quantum dots are made using semiconducting nanocrystals such as CdSe, ZnS, InP, CuInS2, ZnSe, PbSe, PbS, etc. Non-luminescent QDs are also common in some applications and they can be made using metallic and/or magnetic materials. In addition to QDs, nanocrystals can also be made into multi-dimensional shapes such as nanorods and tetrapods.

Nanophosphors (NPs) are luminescent nanocrystals that can vary in size between 50nm to hundreds of nanometers. The optical conversion properties of NPs are generally achieved through doping by small amounts of activating elements (activators). For example, a YAG:Ce nanophosphor is doped using cerium (Ce) as the activator. This enables the YAG particles to absorb high energy UV/blue light and convert it to lower energy yellow-green light or photons.

Doped quantum dots are a class of nanocrystal materials that can be made using colloidal QD processing techniques. This type of QDs have optical properties similar to nanophosphors. In doped QDs, the emission properties and color of the nanocrystal is determined by the dopant while the absorption properties.

Since QDs tend to have a narrower band emission compared to most bulk phosphors, hybrid phosphor-QD systems have also been implemented in some LED-based display applications.  Hence, the narrow spectral feature of QDs can lead to improvement in color gamut and saturation for electronic display technologies.