QLEDs

QLEDs, or quantum dot light-emitting diodes, are devices that use semiconductor quantum dots as the emissive material to generate light. Emission wavelength is determined by dot size due to quantum confinement, enabling highly saturated colors and narrow spectral bandwidth. QLEDs can exist in two related forms: true electroluminescent quantum dot LEDs, where quantum dots form the emissive layer in a diode structure, and quantum dot-enhanced LCDs, where quantum dot films are used to convert backlight light into color.

A typical QLED device stack includes an anode, hole-transport layer, a quantum dot emission layer, an electron-transport layer, and a cathode. When a current is applied, electrons and holes are injected and recombine within the quantum dots, producing photons. Quantum dots are often synthesized as core-shell nanocrystals to improve brightness, stability, and quantum yield. Materials commonly used include cadmium-based CdSe/CdS dots, as well as cadmium-free options such as InP-based dots and perovskite QDs, the latter still under development for stability and longevity.

Advantages of QLED technology include narrow emission spectra with high color purity, potential for wide color gamuts, and the possibility of solution-based, low-cost processing. Challenges involve device stability, particularly for blue emission, long-term operational lifetime, encapsulation to prevent degradation, and environmental concerns over toxic elements in some quantum dots. In consumer electronics, many products marketed as QLEDs use quantum dot color conversion in LCD backlights rather than true emissive QLEDs, while true electroluminescent QLEDs remain primarily in the research and development stage.