LED Modern Applications and Future Advancements

1. LED Modern Applications and Future Advancements Timothy Delf Jason Brownlee February 18, 2005 ECE 3611 Dr. Stanley G. Burns

2. Focus of Report LED Background Structure and Concepts Regarding LEDs Future Advancements & New Technology OLED White LEDs Problems Facing LED Advancements

3. Background Available in multiple wavelengths & colors Long life at 100,000 hours LED's are the light source with the longest life currently available in the world. LED's operate as 12 and 24-volt DC systems High luminescence efficiency Based on the general properties of a simple twin-element semiconductor diode LEDs don’t emit ultraviolet light, which degrades electrical components, and they emit minimal infrared light, the main component of heat

4. Background (Cont.) Extremely quick refresh rate Exceptionally wide color palette Potential for mind-boggling efficiency Numerous Applications (cell phones, signs, stereos, etc.)

5. Colors Available Red Amber Yellow Green Blue White If you have several points, steps, or key ideas use multiple slides. Determine if your audience is to understand a new idea, learn a process, or receive greater depth to a familiar concept. Back up each point with adequate explanation. As appropriate, supplement your presentation with technical support data in hard copy or on disc, e-mail, or the Internet. Develop each point adequately to communicate with your audience.If you have several points, steps, or key ideas use multiple slides. Determine if your audience is to understand a new idea, learn a process, or receive greater depth to a familiar concept. Back up each point with adequate explanation. As appropriate, supplement your presentation with technical support data in hard copy or on disc, e-mail, or the Internet. Develop each point adequately to communicate with your audience.

6. Structure and Concepts Regarding LEDs Heart of a light emitting diode is a semiconductor chip. The diode semiconductor contains several very thin layers of material that are sequentially deposited onto a supporting substrate. Diode chip is mounted in a reflector cup connected to a lead frame, and is bonded to the anode and cathode terminals of the frame through miniature bonding wires. Entire assembly is then encased in a solid epoxy dome lens

7. Structure and Concepts Regarding LEDs A diode comprises a N-type material bonded to P-type material, with electrodes on each end. Connecting the N-type side of the diode to the negative end of a circuit and the P-type side to the positive end eliminates depletion zone. Free electrons moving across a diode can fall into empty holes from the P-type layer. Creates Photons - basic units of light.

8. All diodes can produce “light” Most just don’t produce visible light Wavelength of the photon must be between 400 nm and 750 nm

9. Even if a diode does produce visible light it must also meet these requirements to be effective Must not absorb the photons emitted Instead release photons outward Plastic bulb to concentrate light

10. (a) Diode absorbs photons(b) LED reflects photons(c) Bulb holds photons at top

11. Future Advancements: OLED Organic light-emitting diode-- display device that sandwiches carbon-based films between two charged electrodes When voltage is applied to the OLED cell, the injected positive and negative charges recombine in the emissive layer and create electro luminescent light Beginning to replace LCD technology in handheld devices (PDA, Cell phone, etc)