LEDs (light-emitting diodes) have a reputation for emitting a harsh blue light primarily due to the composition of their semiconductor materials and the emission spectrum of their light output. Here are a few reasons why LEDs can appear harsher in comparison to other types of lighting:
Dominance of blue light: LEDs are based on semiconductor materials that produce light when an electric current passes through them. The most commonly used semiconductors in LEDs are gallium nitride (GaN) and indium gallium nitride (InGaN). These materials naturally emit blue light. To create white light, LEDs often incorporate a phosphor coating that converts a portion of the blue light into other colors. However, the blue component can still be relatively dominant, giving the light a bluish tinge.
Higher color temperature: LEDs are available in a range of color temperatures, which refers to the perceived "warmth" or "coolness" of the light. LEDs with higher color temperatures (in the range of 5000K to 6500K) tend to have a bluish-white appearance, similar to daylight. This can contribute to the perception of harshness compared to warmer light sources, such as incandescent bulbs.
Limited spectral distribution: LED light output often consists of narrow spectral peaks rather than a continuous spectrum like natural light. The presence of sharp peaks, particularly in the blue region of the spectrum, can give the light a somewhat unnatural appearance.
It's worth noting that advancements in LED technology have led to improvements in color rendering and the development of warmer LED options. The introduction of phosphors with better color-mixing capabilities and the utilization of different semiconductor materials have helped address the issue of harsh blue light, making LED lighting more versatile and closer to natural light.