WHAT ARE PHOSPHORS?

Phosphors in general are materials that emit light upon absorbing incident energy. They have a broad range of light color emissions and can absorb and convert energy from various forms such as optical, electrical, even mechanical or thermal.

Phosphors for Lighting and Display Technologies

Phosphors are the most popular choice as color emitters and converters in most lighting and display technologies. In solid-state lighting (LED lamps), phosphors (also known as down-converters or luminophores) have been utilized to convert violet or blue light (usually from a semiconductor source) into colors of lower energy ranging from blue to red in the visible spectral region. They can also absorb and emit energy in the non-visible spectral regions such as ultraviolet and infrared.

Learn more about phosphor applications on PhosphorTech's Technology page.

Phosphor Excitaion and Emission

How are Phosphors Made?

Phosphors are usually made using a stable inert host material (typically oxides, nitrides, silicates, sulfides or selenides) doped in small quantities with activators (such as metal or rare earth ions), which create non-homogeneities or impurities in the crystal structure enabling the emission of light. These impurity centers capture the excitation energy and then release it in the form of light. The type and concentration of the dopant(s) generally determine the color of the emitted light.

Characteristics of LED Phosphors

Due to these desirable properties, phosphors also find applications in a variety of devices ranging from more traditional lighting systems to X-ray imaging and radiation scintillators/detectors.

Solid State Lighting (SSL) and White LEDs

Over the past 50 years, many types of phosphors have been developed to cater to the needs of various types of applications. Among all the various applications, the biggest recent impact of phosphors has been on the solid-state lighting (SSL) industry. Particularly, the use of phosphors with blue-emitting LEDs have recently led to the rapid development of highly efficient white LED lamps with high color rendition (CRI) and a wide range of color temperatures  (CCTs). These developments have helped push LED technology to be the next generation alternative to compact fluorescent lamps and the inefficient incandescent bulbs.

Learn more about solid state lighting applications on the PhosphorTech website.

Types of Phosphors

Some of the most common types of phosphors available are:

  1. Rare earth doped aluminates -  Y3Al5O12:Ce3+
  2. Rare earth  doped orthosilicates - (Ba,Sr,Ca)2SiO4:Eu
  3. Rare earth doped nitrides - (Sr,Ca)2Si5N8:Eu and (Sr,Ca)Si2O2N2:Eu
  4. Rare earth doped chlorosilicates - Ca(8-x)Eux(Mg,Mn)(SiO4)4Cl2
  5. Rare earth doped thiogallates - (Sr,Ca,Ba)Gax(S,Se)y:Eu
  6. Transition metal doped sulfo selenides - ZnSexS(1-x):Cu

While Ce and Eu are the most common dopants used in phosphors, other lanthanide ions such as Pr3+, Tb3+ and Er3+ can also be found in some compositions.

Product Development: Customizing Phosphors for Specific Applications

None of the above individual phosphors offer a complete solution for all LED configurations or color applications. All have their advantages and disadvantages. Phosphor material experts can help design and select combinations of the above materials in order to achieve the required luminous efficiency (lumens/watt or LPW), chromaticity coordinates (CIE), color rendering index (CRI), and color temperature (CCT) demanded by a given application.

Learn more about product development on the PhosphorTech website.

Research, Testing and Development with Phosphors

Phosphor material experts also help investigate the operational limits of these materials and develop techniques for processing and coating on LEDs or lamp fixture components in such a way as to improve both the phosphor and LED lamp performance under extreme operating conditions.

Learn more about research and development on the PhosphorTech website.

Phosphor Excitaion and Emission

For example, in LED devices, phosphors can be configured for use directly on 1) the blue/UV chip, 2) on the package, or 3) even remotely with the blue LED sources.