LEDs for Solid‐State Lighting

A light-emitting diode (LED) is one kind of semiconductor that can emit light. A diode is the simplest solid-state device in electronics. This chapter reviews the historical development of LEDs. The light sources on earth may be classified into two main categories: hot light sources and cold light sources. The presence of the blue light LED implied the completion of the visible light spectrum and the feasibility of implementing white light illumination using LEDs with color mixing schemes. LEDs can cover the whole visible light spectrum with various kinds of semiconductor compounds. The most cost-effective method for generating white light is to use a blue light LED to excite yellow phosphor. LED lighting modules were developed and used to replace the fluorescent light tubes on the trains for saloon interior lighting. The chapter provides certain examples to illustrate the applications of LEDs for general lighting.