QLED TV goes by its name using Quantum-Dot crystals as a Light-Emitting Diode in the backlight that controls the color output. Hence, it replaces the red, green, and blue color filters that the old TV used.
However, an aluminum compound is used by these crystals to make the dots more efficient at passing light through. This makes more accurate and wider contrast.
Samsung says that its QLED TV s use the new filters to display 100% coverage of the DCI/P3 color space. They are so bright that they operate on 4000 nits while a normal HDR operates on 1000 nits.