EE 413

LIGHT-EMITTING DIODE
(LED)

DELMENDO, CIARA MAE GRACE B.

SANTOS, JOHN CARLO F.

2022
LED

INTRODUCTION
❑ A Light-Emitting Diode (LED) is essentially a PN junction
opto-semiconductor that emits a monochromatic (single
color) light when operated in a forward biased direction
❑ It is a semiconductor device that emits light when current
passes through it. When the particles (electrons and
holes) within the semiconductor material carry the
electric current, it produces light.

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INVENTION AND DEVELOPMENT
● 1906 - Henry Joseph Round first reported
“electroluminescence” while experimenting with Silicon
Carbide (SiC)
● 1927 - Oleg Vladimirovich Losev first investigated
and proposed the first LED theory.
● 1955 – Rubin Braunstein of the Radio Corporation of
America first reported on infrared emission from
Gallium Arsenide (GaAs) and other others
semiconductor alloys.
● 1962 - Nick Holonyak Jr. of General Electric Company
invented the first practical light-emitting diode
operating in the red portion of the visible spectrum.
INVENTION AND DEVELOPMENT
● 1976 – Thomas P. Pearsall invented the first LED that
has high efficiency and high brightness. At that time,
semiconductor materials were introduced, which was
suitable for optical fiber communications.
● Throughout the later 1960s and 1970s, further
invention and development produced additional
colors and enabled LEDs to become a readily
available commercial product. `
LIGHT-EMITTING DIODE ANATOMY
HOW LED WORKS?
 HOW LED WORKS?

LEDs are solid-state When certain The heart of LEDs,

semiconductor elements are often called a “die” or
devices. A combined in specific “chip,” is composed of
semiconductor is a configurations and two semiconductor
material with a electrical current is layers – an n-type layer
varying ability to passed through them, that provides electrons
conduct electrical photons (light) and and a p-type layer that
current. heat are produced. provides holes for the
electrons to fall into.
HOW LED WORKS?
HOW LED WORKS?
❑ When a sufficient voltage is applied
to the chip across the leads of the
LED and the current starts to flow,
electrons in the n region have
sufficient energy to move across the
junction into the p region.
❑ Once in the p region the electrons are
immediately attracted to the positive
charges due to the mutual Coulomb
forces of attraction between opposite
electric charges. When an electron
moves sufficiently close to a positive
charge in the p region, the two
charges “recombine”.
HOW LED WORKS?
❑ When the electron and holes
recombine, photons (light) are
created. The photons are emitted in a
narrow spectrum around the energy
band gap of the semiconductor
material, corresponding to visible and
near-UV wavelengths
❑ The color-emitted light of LEDs
depends on the chemical composition
and dominant wavelength of the
semiconducting material used.
 LED

COLOR

❑ The color-emitted light of LEDs depends on the chemical

composition and dominant wavelength of the semiconducting
material used.
❑ LED development began with infrared and red devices made
with GaAs. Advances in materials science have made possible
the production of devices with even shorter wavelengths,
producing light in a variety of colors.

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MAIN N AND P-TYPE DOPANTS USED
 COLOR
Tri-Color LEDs
❏ The most popular type of
tri-color LED has a red
and a green LED
combined in one package
with three leads.
 COLOR
Bi-Color LEDs
❏ A bi-color LED has two
LEDs wired in ‘inverse
parallel’ (one forwards,
one backwards)
combined in one package
with two leads. Only one
of the LEDs can be lit at
one time.
 COLOR
White LED
❏ White light can be formed and produced by the three
colored lights (Red, Green, and Blue) and combine them.
Blue LED
❏ A fluorescent chemical present in the bulb is used to convert
the white light into blue light. The chemical is called Gallium
Nitride. Blue LED is considered the best light to possess
antibacterial properties.
 COLOR
Red LED
❏ The material used for red LED lights is called Gallium
Arsenide Phosphorus (GaAsP)
Green LED
❏ Some manufacturers use phosphor material on the blue
light to convert it into green light. The phosphor materials
are used to convert the high energy spectrum into low
energy.
 COLOR

RGB LED
❏ RGB (Red, Green, and Blue) LED is a combination of the
three different basic colors LED. Other colors are formed
from these three basic colors only. The brightness and
intensity of these three colors can be changed to produce a
different color.
COLOR PRODUCING INORGANIC SEMICONDUCTOR MATERIALS
SIZES, SHAPES AND VIEWING ANGLES

❏ The ‘standard’ LED has a round

cross-section of 5 mm diameter
(T-1 ¾ lamp) “bullet shape”.
❏ LEDs also vary in their viewing
angle (beam of light spreads
out). Standard LEDs have a
viewing angle of 60° but others
have a narrow beam of 30° or
less.
SIZES, SHAPES AND VIEWING ANGLES

LED SHAPES
 LUMINOUS FLUX AND EFFICACY
❏ The luminous flux from a LED varies according to its color,
and depends on the current density the LED die can
manage.
❏ The efficacy of individual LEDs varies by material type,
packaging, radiation pattern, phosphors, and processing.
❏ The average commercial LED currently provides 32 lumens
per watt (lm/W), and new technologies promise to deliver
up to 100 lm/W.
❏ Around 1999, commercial LEDs capable of continuous use
at one watt of input power were introduced. These LEDs
used much larger semiconductor die sizes to handle the
large power input.
 LUMINOUS FLUX AND EFFICACY
❏ In 2002, 5-watt LEDs were available with efficiencies of 18-22
lumens per watt.
❏ In 2005, 10-watt units became available with efficiencies of 60
lumens per watt.
❏ These devices will produce about as much light as a common 50-
watt incandescent bulb, and will facilitate use of LEDs for general
illumination needs.
 LUMEN DEPRECIATION
❏ Lumen depreciation is the lighting attribute most often used
to determine the useful life (minimum maintained
illuminance level) of LED sources.
❏ 50,000 to 100,000-hour life is commonly attributed for LED.
The best LED achieved 70 percent of original light output at
50,000 hours of operation under standard use conditions.
❏ Factors affecting LED’s useful life:
❏ LED chip
❏ The design of heat dissipation
❏ Drive power
❏ Environment
 TYPES OF LED LIGHTS
1. Standard LED Lights

Best for: High-efficiency home and

business lighting.

Standard LED lights are basic bulbs

that have largely replaced traditional
incandescent lights as the most used
type of residential and business lighting.
 TYPES OF LED LIGHTS
2. Can LED Lights

Best for: Ceiling-mounted recessed

lighting.

Can LED lights are specifically

designed to fit into recessed lighting
sockets, which are commonly referred
to as cans.
 TYPES OF LED LIGHTS
3. Dimmable LED Lights

Best for: Adjusting the brightness of the

room.

Dimmable LED lights are a

relatively common option that gives the
user the ability to control the brightness
of the light with a compatible dimmer
switch.
 TYPES OF LED LIGHTS
4. Track LED Lights

Best for: Focused lighting with

compatible lighting tracks.

Intended for direction lighting,

work area task lighting, and
spotlighting decorative features of the
home, track LED lights need to be
installed on compatible lighting tracks.
 TYPES OF LED LIGHTS
5. Smart LED Lights

Best for: Mobile device control and

smart home compatibility.

Smart LED lights can integrate with

existing smart home systems, allowing
users to control the lights with voice
commands or through a mobile app.
 TYPES OF LED LIGHTS
6. Tube LED Lights

Best for: Professional applications in

office buildings, kitchens, and other
workspaces.

Many businesses are installing tube

LED lights as a replacement for
fluorescent lighting tubes because tube
LED lights are high-efficiency options
that come in a wide range of color
temperatures to suit any workspace.
 TYPES OF LED LIGHTS
7. Full-Spectrum LED Lights

Best for: Mood lighting, accent lighting

and customizable lighting.

Commonly referred to as RGB lights,

full-spectrum LED lights can produce a
broad range of color temperatures and
colored light.
 TYPES OF LED LIGHTS
8. LED Security Lights

Best for: Illuminating dark yards,

porches, and paths to the home.

Many LED security flood lights have

dusk-to-dawn sensors that detect the
ambient light level and automatically
turn on the light when it gets dark
enough outside.
 TYPES OF LED LIGHTS
9. Decorative LED Lights

Best for: Decorating for holidays and

adding to the aesthetic appeal of the
home.

There are a variety of decorative

LED light styles, depending on whether
you are looking for classy, modern, or
even holiday lighting.
 TYPES OF LED LIGHTS
10. LED Light Strips

Best for: Customizable accent lighting.

LED light strips often come with

adhesive backing, so they can be
attached to the wall, ceiling, floor,
computer desk, or any other clean, flat
surface that meets the manufacturer's
guidelines.
 TYPES OF LED LIGHTS
11. LED Flood Light

Best for: High power saving led lights

LED flood lights offer bright white light

that spread with broad angle. It is
useful to install in warehouses,
perimeters of houses, theaters,
playgrounds and stadiums
.
 LED LIGHT BULB

❏ An LED light bulb is a solid-state lighting (SSL) device that fits in

standard screw-in connections but uses LEDs (light-emitting
diodes) to produce light.
❏ LED light bulbs are a more environmentally friendly alternative to
incandescent bulbs. LED bulbs use a semiconductor device that
emits visible light when an electric current passes through it. That
property is known as electroluminescence.
LED LIGHT BULB
 LED LIGHT BULB

❏ Epoxy Resin- A material used which is durable without being quite

so fragile.
❏ LED die - More commonly known as an LED
chip, is a small block of compound
semiconductor material that has a p-n
junction (positive-negative junction)
sandwiched between oppositely doped
layers.
 LED LIGHT BULB

❏ Thermal transfer pads- They are primarily used in the LED to

adjust the temperature so that it won’t get damaged from the
negative impact of excessive heat.
❏ Heat sink - A piece of metal the LED chips sit on. Heat needs to be
conducted away from the LED and then cooled somehow – this is
where the heat sink comes in. They provide the path for heat to
travel from the LED light source to outside elements.
❏ Housing - is usually made with aluminum. The housing will still be
warm to the touch, but not as hot as halogen, incandescent or
fluorescent lighting.
 LED LIGHT BULB

❏ Base - LEDs are designed as a direct replacement for existing

light bulbs. They can also be found with any base that
traditional bulbs are available in. There are many types of lamp
bases:
 LED COMPARISON TABLES

LUMENS LED CFL INCANDESCENT

450 4-5 W 8-12 W 40 W

750-900 6-8 W 13-18 W 60 W

1100-1300 9-13 W 18-22 W 75-100 W

1600-1800 16-20 W 23-30 W 100 W

2600-2800 25-28 W 30-55 W 150 W

 ADVANTAGES OF USING LEDs
❏ Sizes
- LED comes in different sizes ranging from small to large. The
small LEDs can be easily attached to the PCB. Here, PCB
stands for Printed Circuited Board. The large LEDs are used in
households, industries, etc.

❏ Low energy consumption

- Light Emitting Diodes consumes around 75% less energy
than fluorescent and incandescent lights. It is because the
LEDs are composed of diode lights, while other lights are
composed of filament light. Diode light is much more
efficient than filament lights.
 ADVANTAGES OF USING LEDs
❏ Different colors
- LEDs can emit light of different colors without using any color
filters. The most common color of LEDs used is soft white and
bright white color light.

❏ Longer life
- The life of an LED can last upto ten years, depending on the
conditions and usage. It is a long-lasting product with 50 times
longer life than incandescent lights and ten times more than
fluorescent lights.
 ADVANTAGES OF USING LEDs
❏ Less prone to damage
- LEDs are solid-state devices that are very less prone to
damage with any external shock.

❏ High Intensity
- LEDs have a higher intensity than other types of lights, such as
fluorescent, halogen, and incandescent. The higher the current
or voltage passes through the LED circuitry, the higher the
LED's intensity will be. A resistor in series with LED is used to
prevent the LED from the large current.
 ADVANTAGES OF USING LEDs
❏ Directional
- Directional means that the LED emits the light in a single
direction; The incandescent and fluorescent light sources emit
light in all directions. The single or specific directional
capability of the LED saves energy and light.

❏ Cooling effect
- LED does not emit any radiant heat. It increases the cooling
load inside an LED.
 ADVANTAGES OF USING LEDs
❏ Improved Safety
- Improved safety of LEDs is one of the essential advantages. All
the light sources emit heat, which can sometimes be
hazardous. LEDs can effectively operate at low voltages. It
emits no forward heat or any polluting radiations. Hence, it is
safe to use an LED in households or projects.

❏ Different Shapes
- LED comes in different shape styles. We can select an LED as
per our requirements.
 ADVANTAGES OF USING LEDs
❏ Efficiency
- The efficiency of an LED is much greater than that of
incandescent and fluorescent lights. There is no effect of size,
color, and shape on the efficiency of an LED.
❏ Immediate Illumination
- Improved safety of LEDs is one of the essential advantages. All
the light sources emit heat, which can sometimes be
hazardous. LEDs can effectively operate at low voltages. It
emits no forward heat or any polluting radiations. Hence, it is
safe to use an LED in households or projects.\
❏ Reliability
- LEDs are much more reliable than other types of light sources.
LEDs can withstand vibrations, fluctuations and can also work
on colder temperatures. It is due to the absence of fragile parts
and filament in an LED.
 ADVANTAGES OF USING LEDs

❏ Reliability
- LEDs are much more reliable than other types of light sources.
LEDs can withstand vibrations, fluctuations and can also work
on colder temperatures. It is due to the absence of fragile parts
and filament in an LED.
 DISADVANTAGES OF USING LEDs

❏ High cost
- LED has a high cost as compared to other types of light
sources. But, there is a continuous drop in prices over recent
years. Hence, LEDs have replaced the use of CFL and
incandescent bulbs.

❏ Winter effects
- LED does not emit heat as compared to other light sources.
LED lights used as a signal light do not clear the fog or snow,
which may lead to accidents due to these lights' invisibility.
 DISADVANTAGES OF USING LEDs

❏ Temperature Sensitivity
- The overuse of LEDs in high ambient temperature can fail. To
overcome such issues, a heat sink is required. The heat sink is
defined as a process to pass excess heat of a mechanical or
electronic device to the air or coolant (liquid). It dissipates the
excess heat from the device, thus maintaining its temperature.

❏ Effect on wildlife
- Some intense blue and white color LEDs can disturb turtle
movement on land when used near hatches.
 LED APPLICATIONS
❏ LEDs may be more expensive than incandescent lights up front,
because they’re built around advanced semiconductor material,
their lower cost in the long run can make them a better buy.

Dot Matrix LED

Seven-segment LED
LED APPLICATIONS

Exit and Emergency Sign Backlight LED

 LED APPLICATIONS

Cyclist Belt LED

LED for Task Lighting
 LED APPLICATIONS
❏ Main drivers for conversion to LEDs
- higher efficiency, long life, reduced maintenance, and increased
and superior visibility, making LEDs a more cost-effective lighting
option for a wide range of situations.

❏ Examples of different usage of LEDs

(a) seven segment in showing numbers in calculators and

measurement instruments.
(b) in dot matrix arrangements for displaying messages displays in
public information signs (banks, hotels, airports and railway
stations and as destination displays for trains, buses, and ferries).
 LED APPLICATIONS
(c) remote controls for TVs, VCRs, etc., using infrared LEDs.
(d) traffic signals
(e) pedestrian signs
(f) highway sign panels
(g) railroad signals
(h) marine navigational lights
(i) emergency beacon or strobe lights at airports
(j) exit signs
(k) channel letters
(l) street signs
(m) moving messages
(n) marquis
 LED APPLICATIONS
(o) building façade graphics
(p) scoreboards.
(q) walkway lighting
(r) floor of spaces that are often dark or that only have low level
lighting (movie theaters and passenger aircrafts)
(s) car brake and indicator lights in automobile
(t) bicycle lighting
(u) task lighting for desks, workstations, and display-cases
(v) downlighting for elevators and emergency applications
(w) appliance lighting for refrigerators and vending machines
(x) portable lighting for flashlights or torches
(y) miners’ and dive lights.
 LED APPLICATIONS
(z) indicators for audio and video equipment.
(aa) fiber optic communications
(ab) in photographic darkrooms
(ac) backlights for LCD screens.
(ad) disco/club lighting products.
(ae) projectors
(af) movement sensors (i.e. in mechanical and computer mice and
trackballs)
(ag) pulse oximeters, both a red and an infra-red LED are used.
(ah) phototheraphy (use of light for healing process)
(ai) christmas lights and other for decorative display.
LED APPLICATIONS

❏ Decorative Light
- LEDs or multicolor LEDs are used as decorative
lights with the two supply wires that can be
inserted as a switch when voltage is supplied to
the two-wire lead, the different LED lights.
❏ Flashlights
- LEDs are widely used as a flashlight in
households, industries, etc. It is also present on
the front helmet of miners. The working of such
flashlights does not require any external supply.
These flashlights include battery cells that
provide energy to LED to light.
LED APPLICATIONS

❏ Automotive headlights
- LEDs are used as headlights in different
automotive devices, such as cars, bicycles, trucks,
etc. It is because of the directional capability of
LEDs, which spreads the lights in one direction. It
also provides better design, increased safety,
and high luminous efficiency.
LED APPLICATIONS

❏ Data Communication
- The use of LEDs can produce high data
bandwidth. Due to this reason, VLC was
introduced. VLC or Visible Light Communication
is a type of data communication that uses visible
light for communication. It has replaced the use
of radio bandwidth for data transmission.
LED APPLICATIONS

❏ Camera Flashes
- Smartphones and cameras use LED flashes for
enhanced photography, even in low light
conditions. It means that LED flashes work as
artificial light. LEDs as flashes are preferred over
other light sources due to low energy
consumption, softer, and better illumination.
LED APPLICATIONS

❏ Optical Fiber Communications

- The light emitter in Optical fiber is an essential
part of the system. Two types of LEDs used in
the optical fiber are called Surface Emitting, and
Edge Emitting LED. LEDs convert the electrical
energy into light energy transmitted between the
two ends of the optical fiber.
 ENVIRONMENTAL AND DISPOSAL
ISSUES
❏ LEDs are solid-state devices, they do not contain mercury, glass,
filaments, or gases. Because LEDs are small and have long
lifetimes, their use might reduce the material flow entering the
waste-stream.
 LEDs: THE FUTURE OF LIGHTING

❏ LEDs are finding their way into many new applications within the
lighting community. Research by dozens of companies is underway
to deploy LEDs even further. The ultimate goal is to move these
special light sources into common usage for general lighting
wherever applicable.
LED

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