White LED Phosphor Technology Analysis

This publication has been discontinued on September 5, 2011.

Introduction

Abstract

Light Emitting Diode (LED) is a semiconductor that emits light when electrical current flows through the diode, causing electrons and holes to meet at the same part of the semiconductor, called the junction. When the electrons fill the holes, energy is released in the form of light. Currently, white LED is being incorporated into a variety of applications including flat panel display (FPD) backlights, automotive lamps, general lighting, etc. and its use is growing.

White LEDs have several advantages over incandescent and fluorescent lighting. One advantage is the lack of mercury, a poisonous material that is harmful to the environment and banned by the RoHS directive. Although fluorescent lighting has been used for its power saving benefits, almost all fluorescent tubes require the use of mercury. Another benefit of LEDs is the solid-state nature making the light emitting semiconductor very durable and with a long lifetime of up to 100,000 hours. An epoxy resin is used for the LED enclosure that allows the most amount of light to escape from the semiconductor, focuses the light and protects the LED semiconductor from external elements making the LED virtually indestructible. In comparison, fluorescent lighting generally is limited to 50,000 hours while candescent lighting is significantly shorter and both are easily susceptible to physical damage. LED-based lighting is expected to supplant both incandescent and fluorescent lighting in the future.

There are generally two semiconductor materials that are used to manufacture LEDs: gallium nitride (GaN) and indium gallium nitride (InGaN). GaN transistors are used for its ability to work in hot temperatures and high voltages. InGaN is a semiconductor material that is the result of a mixture of GaN and indium nitride (InN). InGaN can also be used in high temperature settings.

The white LED package can be manufactured using a single LED chip or multiple LED chips. In a single LED chip package, there are two methods of generating white light. White light can be generated by using a blue LED chip and applying a yellow phosphor or by using a ultra-violet (UV) LED chip. For multiple LED chip packages, two or three LED chips can be used to generate white light. For instance, in a three LED chip package design, a red LED chip, a green LED chip and a blue LED chip can be used to generate white light.

Table of Contents

1. Introduction

• 1.1 Outline
• 1.2 Investigating Methods
• 1.3 What is a Phosphor?
• 1.4 Developmental Process of Phosphor

2. Fluorescence of a White LED Phosphor

• 2.1 Principle of Fluorescence
• 2.2 Efficiency of a Phosphor
  • 2.2.1 Selection of an Active Material
  • 2.2.2 Selection of the Matrix
  • 2.2.3 Selection of Sensitizer
  • 2.2.4 Energy Transmission in a Phosphor
  • 2.2.5 Human' s Color Perception
  • 2.2.6 Colors of a Phosphor
• 2.3 Synthesis Technology for a Phosphor
  • 2.3.1 Solid-phase Reaction
  • 2.3.2 Liquid-phase Reaction
  • 2.3.3 Gas-phase Reaction
  • 2.3.3.1 Spray Pyrolysis Deposition
  • 2.3.3.2 Ultrasonic Spray Pyrolysis Deposition
  • 2.3.4 Characteristics of fluorescence
  • 2.3.5 Characteristics of fluorescent ion (active agent)

3. Manufacture of White Phosphor

• 3.1 Manufacturing Method
• 3.2 Conditions for White LED Phosphor
• 3.3 Evaluation of a Phosphor
• 3.4 Trend of Development
  • 3.4.1 Development Trend of Blue LED Phosphor
  • 3.4.2 Development Trend of UV LED Phosphor

4 Development and Potentiality of a New Phosphor

• 4.1 Quantum Dot Phosphor
• 4.2 Hybrid Phosphor
• 4.3 Requirements for a New Phosphor
  • 4.3.1 Evaluation of White LED Light Element
  • 4.3.2 Evaluation Items for Reliability of a Phosphor
• 4.4. Potential Application of White LED

Related Reports