LED & Phosphor Technology Overview

White light LEDs are produced by coating phosphor powder on LED chips. There are three mainstream phosphor-based solutions for white light generation, but technical limitations still restrict their large-scale application in the general lighting industry.

1. Three White Light Implementation Solutions

1.1 Blue LED Chip + Yellow Phosphor

Blue LED chips are coated with yellow phosphor that can be excited by blue light. The blue light emitted by the chip and the yellow light emitted by the phosphor complement each other to form white light. This technology is monopolized by Nichia Corporation. Due to the discontinuous emission spectrum of Ce³⁺ ions in the phosphor, this solution has poor color rendering, cannot meet the requirements of low-color-temperature lighting, and has insufficient luminous efficiency, which needs to be improved by developing new high-efficiency phosphors.

1.2 Blue LED Chip + Green & Red Phosphors

White light is obtained by combining the blue light from the chip with the green and red light from the phosphors. This method provides better color rendering, but the effective conversion efficiency of the phosphors is low, especially the efficiency of red phosphors needs to be greatly improved.

1.3 UV/Purple LED Chip + Multi-color Phosphors

Long-wave ultraviolet (370nm-380nm) or purple light (380nm-410nm) emitted by LED chips excites RGB or multi-color phosphors to achieve white light output, with better color rendering. However, most high-efficiency red and green phosphors used in this method are sulfide-based materials, which have poor luminous stability and large light decay. Therefore, developing high-efficiency, low-light-decay phosphors for white LEDs has become an urgent task.

2. Phosphor Application in Color LEDs

Lanjin Optoelectronics is one of the earliest domestic institutions engaged in the research of high-efficiency and low-light-decay phosphors for LEDs. Recently, through joint research with our Taiwan partners, we have successfully developed a variety of color LEDs using phosphor technology.

The advantages of using phosphors to produce color LEDs are as follows:

• Improve Luminous Efficiency: Phosphors can convert high-efficiency LED light into target wavelengths to improve the luminous efficiency of low-efficiency bands. For example, phosphors provided by Lanjin Optoelectronics help Taiwan manufacturers produce high-efficiency "apple green" LEDs for mobile phone backlights, achieving good economic benefits.
• Reduce Production Waste: It is difficult to accurately control the luminous wavelength of LEDs, resulting in wasted products. Phosphors can convert these off-wavelength "waste products" into required colors for reuse.
• Optimize Light Color: Phosphors can make LED light softer or more vivid to meet different application needs.

At present, phosphors are most widely used in white LED fields. The application of phosphors in color LEDs is still in the initial stage, and Lanjin Optoelectronics will continue to carry out in-depth research and development to promote technological progress.