A Fascinating Behind-the-Scenes Look at Electroluminescent Quantum Dots

What are quantum dots? Quantum dots(QDs) are tiny particles in crystalline semiconductor materials, with sizes of a few nm, usually 2-10 nanometers in diameter. This is the size of a large molecule, although it’s smaller than DNA. They’re usually made up of hundreds or thousands of atoms in a rigid lattice. These semiconductor particles are magical particles and are the hottest topic discussed in the display technology field in a very long time. As they can emit light of a specific wavelength when an electric current is applied or exposed to light. Besides, this emission wavelength can be adjusted by changing the size, shape, material, or doping quantum dots. Typically, smaller quantum dots, such as 2-3 nm, can emit light with a shorter wavelength (blue-green spectrum region), while larger quantum dots, with 5-6 nm, can emit light with a longer wavelength (orange, red). In addition, their fluorescence lifetime is also related to their particle sizes. For larger quantum dots, their life cycle is longer because the electron-hole pairs can be captured at more closely spaced energy levels. Electroluminescent quantum dots QD light-emitting diodes (LEDs) are a kind of light-emitting device technology and is considered as the next generation of display technology after organic light-emitting diode display. As QD-LEDs are organic light-emitting diodes with high brightness, high efficiency, long life, flexibility, high quality and low processing cost. As QD-LEDs are suitable for manufacturing via the coating process, they are also expected to reduce the manufacturing cost for larger screens. A typical QD material is Cd-based QDs. Cd-based quantum-dot light-emitting diodes have been extensively explored for applications in display and lighting. Red, blue, and green? Quantum dots for light-emitting diodes have been regarded as one of the promising light sources in display applications due to their excellent color saturation, high brightness, spectral tunability and low processing cost. So far, the performance of red and green QD-LEDs has been significantly improved by optimizing the structure of QD materials and devices and further understanding of their luminescence mechanism. For instance, Creative Diagnostics DiagNano™ Cd-Based QDs can exhibit high external quantum efficiency (EQE), the EQEs of red- (R-), green- (G-), and blue- (B-) QLEDs are higher than 18%, 15% and 8%, respectively. To be more specific, the Red-emitting InP/ZnS quantum dots are stabilized with oleylamine in n-octane, PL 630±10 nm, FWHM (nm)~45 nm, Max EQE ~15%; green-emitting InP/ZnS quantum dots are stabilized with oleylamine in n-octane, PL 525±10 nm, FWHM (nm)~37 nm, Max EQE ~10%; and blue-emitting InP/ZnS quantum dots, stabilized with dodecanethiol in n-octane, PL 470±10 nm, FWHM (nm)<45 nm, Max EQE ~1%.