Weaknesses of LEDs

Although LEDs bear several imperfections which need to be improved in the future, they possess many advantages over conventional incandescent lamps. As a next-generation light source, offering benefits such as its compact size, long lifespan, energy-efficiency, and durability, LEDs have aroused tremendous interest among different countries and regions. With the rapid advancement of LED industry all over the world, we believe that these imperfections of LEDs will be corrected in the foreseeable future.

1. Bad Color Revivification

The general color rendering index of LEDs has been relatively low in the past, and the color reversion of LEDs is does not compare to that of incandescent bulbs. We all know that the lighting quality of incandescent lamps is excellent (CRI 100%) while white LEDs provide color rendering indices between 70% and 85%, better for daylight (6,000 K) than for warm white (2,900 K) LEDs. However, with the improvement of phosphors and the technological upgrade of LED materials, some LEDs’ CRI has been enhanced to 90%.

2. Single LED’s Power is still Low

Due to the low power of a single LED, its luminance remains fairly low. Thus, more LEDs are required to be connected in parallel, such as in automobile backlights. More LEDs lead to higher cost, although the cost of a single LED is not high. At present, a single high-power LED is quite expensive yet its luminous intensity is just around 5,000 mcd.

3. Short Illumination Range

Although many methods have been developed to improve the brightness of the LED light source, it remains difficult to extend its illumination range. As LEDs emit scattered light, the illumination range is only tens of meters. Thus, LEDs are quite suitable for short-range lighting application. Nevertheless, with the development of new technology, LED’s illumination range is expected to expand gradually.

4. “Yellow Ring” Phenomenon

Due to the immature process of white light LEDs and the error when configure the reflective cup and lens, “Yellow Rings” that frequently appear in white light LEDs are difficult to eliminate. In recent years, blended phosphor has been adopted to generate ideal white light with high CRI.

Take the blue light LED for example, it activates the mixture of YAG phosphor and green or red phosphor to generate white light. If the blue light LED, after activating YAG phosphor, emits white light with a “yellow ring”, green light (wavelength 500nm～530nm) phosphor may be added to counteract the unwanted yellow light. Similarly, if the blue light LED, after activating YAG phosphor, emits white light with a “blue ring”, red light phosphor without sulfide may be added to counteract the unwanted blue light. These methods can regulate not only the color coordinates but also the color temperature of LEDs, without affecting the lifespan of the LEDs.

5. Heat Dissipation

Heat generated by the acting light emitting chip for the LED must be absorbed to maintain normal working temperature to prevent over-heating or damaging the chip. Industry players strive to develop more efficient heat-dissipating materials.