Quantum dots are semiconductor particles that have a radius between 1 and 10 nm. Due to their semiconductor structure, when they are excited, they emit light in a narrow range of frequencies which is adjusted by changing the diameter of the particle. Quantum dots with shorter diameter emit shorter wavelength light (blue), and those with a greater diameter longer wavelength light (red). Quantum dots are used for LED (Light Emitting Diode) lighting, but not as much as in screen making technologies. Currently, their most famous application is in QLED (Quantum dot Light Emitting Diode) LCD (Liquid Crystal Display) TVs, where they significantly increase colour spectrum. In addition, their application is on the rise in production of tablet and mobile screens, and the most famous companies that use them are Amazon, LG, Samsung and Sony. Medical applications are still being investigated and are expected to be used in photodynamic therapy for cancer treatment. Application of quantum dots is not widespread as could be because the compounds contain cadmium, declared as a dangerous substance. Today, alternatives are compounds that do not contain cadmium.