We need to introduce the concept of quantum confinement. In modern QLED TVs, tiny particles called quantum dots (QDs) are used. These quantum dots are so small that they can control the behavior of electrons in a unique way. When an electric current passes through them, they emit light at very specific wavelengths, creating bright and pure colors. 

Quantum confinement occurs when a material is so small—typically on the scale of nanometers—that it restricts the motion of electrons to a very limited space. This confinement changes the energy levels of the electrons, causing them to behave differently than they would in a larger, bulk material.  

In a quantum dot, the size of the particle directly affects the color of the light it emits. This is because the energy difference between the electron levels in a confined space determines the wavelength (or color) of the light. Smaller quantum dots have more broadly spaced energy levels, emitting light with shorter wavelengths (toward the blue end of the spectrum). In larger quantum dots, the energy levels are more closely spaced, so they produce light with longer wavelengths (toward the red end).