Lighting Systems based on LEDs LED components

Although they have invaded our daily lives in less than a decade, Light Emitting Diodes (LEDs) are the fruit of a slow and chaotic evolution, as much the result of chance, intellectual curiosity and scientific and technological research. From their first observation in 1907 to the advent of efficient LED lighting in the late 2010s, their development has been the result of a series of innovations, mainly in the fields of materials science and semiconductor physics. Essentially monochromatic, LEDs have also been able to enter the lighting field and produce white light through various technological solutions, the main one being a "blue LED + phosphor" combination.

Every stage in the manufacture of an LED is a real technological challenge. Whether it's the production of substrates, dopants, integration, realization, resistance to thermal, electrical or mechanical stress at chip level, at component level or its integration into a system, electrical connections (bonding) or its encapsulant, each interface, each material and each function (blue light emission by the chip, phosphor excitation and white light emission, diffusion and protection by the encapsulant...) constitute stages in their own right in the development of an LED.

The research and implementation of LED energy management is without doubt the most fundamental critical point in the study of LEDs, since an increase in heat induces not only a drop in energy efficiency, but also a considerable drop in lifetime.

Since the 1990s, all the efforts made in this field have contributed to increasing the robustness, reliability, lifetime and luminous efficacy of LEDs, while at the same time implementing processes that make mass production possible with considerable levels of reproducibility.

Furthermore, the semiconductor industry, and therefore also the LED industry, is inexorably moving towards the impasse of an unresolvable equation, where the production of raw materials (notably gallium and indium) remains considerably lower than current needs. Short-term projections only confirm this impending shortage, with China holding a virtual monopoly in terms of both resources and manufacturing.

After an introduction to the fundamentals of LEDs, preceded by a brief history, this article looks at the LED from the point of view of the component, materials and encapsulation, before introducing the notions of efficiency and techniques for producing white light from this intrinsically monochromatic component.

The concept, standards and definitions of LED lifetime are also discussed.

Lastly, in parallel with the development and improvement of existing technology, notably with Photonic Crystals (PCs), other...