How LEDs Work: Summary

How LEDs Work: Overview

• LEDs (Light Emitting Diodes) operate on semiconductor principles, producing light through electron movement, not heat or fluorescence.

Semiconductor Basics

• Diodes are fundamental components that allow current to flow in one direction.
• Diodes consist of N-type (excess electrons) and P-type (deficit of electrons or holes) materials joined at a junction.
• Doping (adding impurities) creates N-type and P-type semiconductors.

Electron Movement and Light Production

• When forward-biased by connecting N-type to negative and P-type to positive, electrons are attracted to holes, creating a depletion zone.
• Light is emitted when electrons drop from a higher energy level to a lower one, releasing energy as photons.
• The energy gap (difference between levels) determines the photon energy and thus the light frequency (color).

Challenges in Light Extraction

• TIR (Total Internal Reflection) impedes light extraction from the LED die, requiring careful design.
• Early LED dies had poor light escape efficiency due to high refractive indices; improvements included varied die shapes and encapsulations.

Innovations for Better Efficiency

• Current technologies utilize photonic lattices to enhance light extraction by redirecting and diffracting light escaping the semiconductor.
• Recent developments have achieved light extraction efficiencies exceeding 70%.