History Of Developing Electrical Sources Of Light

Introduction

Nightlife seems to be the norm in this modern day and age. People never really thinks about light ever since we have been granted the luxury of having a source of light with just a flick of a switch whenever we need it. This was however not the case for people a few centuries ago (Brox, 2011). In the very beginning of life, humans relied solely on sunlight and moonlight to navigate their way through the wild. It wasn’t until about 99,998 BCE when the first manmade light was in control of mankind – fire (Carlson, 2018). Torches were made from a wet wooden stick wrapped with a rag soaked in flammable liquid and its tip ignited. This enabled people to explore dense jungles in the night or dark caverns, and also to protect them against wild predators. Comment by Isaac Lin: Retrieved on 09/01/2019 Comment by foo weihan: Comment by foo weihan: Comment by Isaac Lin: https://www.timetoast.com/timelines/the-evolution-of-the-light

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In the 18th century, candles and oil lamps replaced the cumbersome fire torch. The wealthy used beeswax and spermaceti (whale oil) candles. The middle class used cheap tallow candles while the poor would use rush lights or crafted candles made from reeds dipped in animal or vegetable fat and ignited (Bermudez, 2014). Although lighter and more portable, these new inventions were prone to cause accidents (Brox, 2011). To make matters worse, these early sources of light could only emit a faint light, smoked, and even gave out foul odours especially when used indoors (Bermudez, 2014). Comment by Isaac Lin: https://www.delmarfans.com/educate/basics/who-invented-light-bulbs/ Comment by Isaac Lin: https://www.independent.co.uk/life-style/gadgets-and-tech/features/artificial-light-how-man-made-brightness-has-changed-the-way-we-live-and-see-forever-2282563.html

The discovery of gas lamp took place in the 19th century, where kerosene or paraffin were the main fuels for the lamp. Gas lamps were in general cleaner and emitted brighter light compared to candles and oil lamps. Magnificently, the flame would not be doused by water nor extinguished with breath. Gas lamps were especially popular and were quickly spread all over Europe and America. By the mid-19th century, gaslight had lit up major cities throughout these continents since they were implemented as street lights (Brox, 2011). This great implementation is credited for reducing crime rates as a whole and also increasing literacy in many areas (Bermudez, 2014).

During the turn of the century however, gas lamps were steadily replaced by electric arc lamps, a technology first successfully demonstrated in 1809 by Sir Humphry Davy at the Royal Society of London as shown in Figure 1. The lamp however was too brilliant for domestic use. Therefore, the search for a more practical and energy efficient electric light occupied many inventors throughout Russia, Europe and the United States in the 19th century. Thomas Edison and his team of 14 contractors would display the first viable incandescent bulb to the public in Menlo Park, New Jersey in late 1879 as Figure 2 illustrates. This new breakthrough illuminated mostly major cities until electricity was introduced everywhere as power grids expanded rapidly in the 20th century (Brox, 2011).

Edison’s light bulb remained dominant until new and improved versions of the incandescent lamp, namely the halogen light bulb hit the market in 1959. Later the compact fluorescent light bulb (CFL), another great invention by Edward E. Hammer appeared on the market in 1980s as Figure 3 shows followed by the LED later in 2008 (Bermudez, 2014). As of today, LED light bulbs seems to be replacing lighting as a whole throughout the world.

History and Development of the LED

Light-emitting diode is an electrical component that generates light when connected to a direct current (DC). Its working principle lies on the concept of electroluminescence. It is able to generate light in the visible spectre, in infrared, and ultraviolet (History of Lighting, n.d.). LED is by far the most energy-efficient lighting technology available for any use. The light emitted is also projected in a single direction, eliminating the need for diffusers and reflectors like other conventional lightings (J&K Lighting Agency LLC, n.d.). Comment by Isaac Lin: http://www.historyoflighting.net/light-bulb-history/history-of-led/ Comment by Isaac Lin: https://www.shineretrofits.com/knowledge-base/lighting-learning-center/a-brief-history-of-led-lighting.html

In 1961, James R. “Bob” Biard and Gary Pittman from Texas Instruments discovered that gallium-arsenide diode emits infrared light when connected to current while working on a laser diode as shown in Figure 4 (History of Lighting, n.d.). The following year, the first visible red diode was developed by Nick Holonyak Jr. Whereas in 1972, the first yellow diode was discovered by M. George Crayford. He also improved the red diode and developed the red-orange diode at the same time. In the same year, the violet diode was developed by Herbert Maruska and Jacqued Pankove. These early versions of the LED were used as indicator lights and calculator displays during the 1970s (Bermudez, 2014.).

In 1993, Shuji Nakamura of Nichia Corporation developed the first bright blue light emitting diode as shown in Figure 5 (Bermudez, 2014.). It laid the foundation for the development for a more cost-efficient and functional white LED light (J&K Lighting Agency LLC, n.d.). In the later days, scientists began experimenting with red, blue, and green diodes by coating them with phosphors to make it appear white (Bermudez, 2014.). Today, Light emitting diodes can be made in one or more colours (History of Lighting, n.d.).

During the early 2000s, LED lights finally made an appearance on the market for commercial use (History of Lighting, n.d.). To encourage the development of ultra-efficient solid-state lighting products, the U.S. Department of Energy announced the L Prize Competition in the year 2008. And in the following year, Philips Lighting North America participated with its LED bulb in the competition’s 60-Watt replacement category. In 2011, they were the winner for the L Prize 60-Watt replacement category. The winning LED bulb costed $40 and was said to have a lifep of about 27 years (Bermudez, 2014.).

Today, LED bulbs costs 85% less than LED bulbs back in the early 2000s, making them a favoured choice of lighting in homes, offices, businesses, and also public places. When comparing with incandescent bulbs, LED bulbs are six to seven times more energy-efficient cuts energy consumption by 80%, and also last about 25 times longer (Bermudez, 2014.).

Mechanism of LED

A light-emitting diode is a specialized form of p-n junction diode that emits light when activated. The material used in the junction has to be a compound semiconductor which is basically aluminum-gallium-arsenide (AlGaAs). In its original state, the atoms of this material are strongly bonded. Without free electrons, it is impossible to conduct electricity. By adding impurities, which is known as doping, extra atoms are introduced and disturb the balance of the material effectively. These impurities in the form of additional atoms are able either to provide free electrons (N-type) into the system or suck out some of the already existing electrons from the atoms (P-Type), creating holes in the atomic orbits (Jain, 2017).

Figure 6 shows the working principle of a diode. N-type is in red colour and it contains the electrons while the electrons are indicated by the black circles. The P- type is in the blue colour and it contains holes, they are indicated by the white circles. Electrons and holes will move towards each other across the junction attracted by their opposing electrostatic charges. When a hole and an electron meet, they will form a neutral area of paired holes and electrons. This continues until all the holes and electrons are used up, and an area called depletion zone is formed as illustrated in Figure 7. In the depletion zone, the semiconductor acts as an insulator because there are no free electrons to carry current (Wood, 2008).

By connecting the P-type material to the positive terminal of a power source and the N-type material to the negative terminal, the diode is said to be forward-biased. The electrons are pushed from n-type to p-type while the holes are pushed in the opposite direction. This causes the depletion zone to be narrowed and electrons will flow in forward direction with less resistance as shown in Figure 8. Hence, there will be recombination due to the flow of these charge carriers. The recombination indicates that the electrons in the conduction band of higher energy level jump down to the valence band of lower energy level.

Based on quantum theory, when the electron in the conduction band comes down from the higher energy orbital to the lower energy orbital, energy in the form of photons is released when the electrons and holes are recombined as shown in Figure 9. The photons that are emitted have energy equal to or greater than the band gap energy for the diode and hence they are able to escape from it in the form of light. This whole phenomenon is called electroluminescence phenomena (Jain, 2017).

The difference in the energy levels will determine the energy of the photon. The higher the energy of photon, the higher the frequency of the light. The emitted photon energy is approximately equal to the band gap energy of the semiconductor. The following equation relates the wavelength and the energy band gap (Elprocus, n.d.). Where is the energy band gap, is Plank’s constant, is the frequency of electromagnetic radiation, is the speed of the light and is denoted as a wavelength of an electromagnetic radiation.

From the above equation, we can say that the wavelength of electromagnetic radiation is inversely proportional to the energy band gap. As we all know, the colour of visible light depends on its wavelength. To obtain various colour of a LED, materials of different band gap energy forming the p-n junction are used. Therefore, we can conclude that the colour of light emitted by LED is not determined by the colouring of the LED’s plastic body but the overall wavelength of the photon light emissions (Electronic Tutorials, n.d.). Table 1 shows the typical characteristics of different LED which uses various semiconductor material.

Application of LED

The major purpose of LED is to illuminate objects and even places. Its application can be seen almost everywhere due to its compact size, low consumption of energy, longer lifetime and flexibility in terms of use in various applications.

LED-based surgical lights have become the technology of choice for overhead illumination in hospital operating rooms. This is due to the fact that LED surgical lights produce a high-intensity white light with a high colour temperature for optimum visibility. This effectively reduces eye strain and mental fatigue of the surgical staff which in return promotes their concentration and energy levels at all times especially during medical procedures. Innovative colour-control technology grants surgeons the unique ability to adjust the colour temperature of the output light while maintaining high colour rendering. It allows optimum surface contrast and enhanced tissue differentiation at the surgical site. LED surgical lights also do not radiate heat on the surgical area unlike the conventional instruments used. This reduces the air cooling requirements of the operating rooms thus creating extra energy savings. The lack of infrared and ultraviolet emissions does help in preventing the possible interference of light with sensitive chemical compounds, diagnostic sensors or treatments in the medical environment (Kawa, 2010).

Apart from that, LED has also been used in the exterior and interior lighting in the manufacture of automotive. Manufacturers have successfully adopted LED technology for rear lights, brake lights, indicators and daytime running lights, as costs have fallen and advances have provided more flexibility. LED was once said to be unsuitable to be used in the headlight due to its emission of light through a small lens that creates a beam within a specified arc. LED has advanced so quickly that it can be now used in headlight as high brightness white LEDs now emit light at a similar colour temperature to that of day light.

The illumination of the light can be controlled to avoid dazzling other drivers. The lifetime of a vehicle can also be extended as proper thermal management is given. One of the advantages of LED headlamps over conventional lamps is it is smaller in size, therefore providing greater freedom in design to suit driving conditions. They also make it possible to produce all-in-one units that incorporate indicators, daytime running lights and high or low beams in a single unit, hence making the assembly and repair of automotive to be easier (Pawsey, 2016).

Moreover, LEDs can also emit light waves that are invisible to the human eye which is known as infrared waves. Infrared (IR) LEDs are often used in security systems across the globe, including the military devices manufactured by Larson Electronics which are used by the US Military (Larson Electronics, n.d.). Infrared LEDs are typically used in security cameras. It allows the capture of images no matter it is in the day or night. Compared to night vision goggles which simply detect infrared light, infrared cameras both detect and emit infrared light according to the ambient light available, at the same time monitoring and adjusting the light level in the recorded area. Infrared LEDs are also used in most remote-control devices whereby a beam carrying instructions in binary code is sent from the remote control to the device which receives these commands and performs the action given (Elemental Led, n.d.).

The Comparison between Incandescent Lamp with LED lamps and the Advantages and Disadvantages of Using LEDs

Apart from LED, incandescent lamp is one of the light sources which was developed by Thomas Edison in the late 1800s. An incandescent lamp functions by heating the filament to an extremely high temperature (around 2700 Degree Celsius) to emit light (Chandler, 2016). However, many nations started to ban or phase out incandescent lighting due to its energy-inefficiency and it was replaced by Compact Fluorescents (CFLs) and Light-Emitting Diodes (LEDs). Based on International Energy Agency (2010), there were more than 37 countries had adopting the policies to phase-out incandescent lights at the end of year 2006. Table 2 compares LED and incandescent lamp. Below also compares and describes the advantages and the disadvantages of a LED with an incandescent lamp.

Firstly, LED and incandescent lamp has different ways of generating light. When power is applied, LED generates light with the movement of electrons that creates visible light whereas incandescent lamp generates lamp by heating the filament.

The most significant advantage that causes LED to replace other types of light is its energy-efficiency. In the 21st century, people are more concerned about saving energy and more inventions are being released to the world. LED is considered energy efficient because most of the input power is used to generate light, while incandescent lamp releases 90% of the input power as wasted heat (Stouch Lighting, n.d.). By comparing the power needed by each lamps, LED uses 6-8 watts but incandescent lamp uses 60 watts (USAI Lighting, n.d.). Also, LED produces lesser amount of heat due to its low power consumption, so the use of LED does not increase much in the ambient temperature (Singh, 2009). However, incandescent lamp emitted more heat as the filament needs to be heated to extremely high temperature to generate light and 90% of the energy is released as wasted energy. This also shows their energy efficiency in which LED is 6-7 times more efficient than incandescent lamp and it could cut energy consumption by 80% (Bermudez, n.d.). Hence, LED mostly fails by dimming with time while incandescent lamp will stop working completely (Stouch Lighting, n.d.).

Besides, LED has a longer lifep and it can last up to 50,000 hours. In contrast, incandescent lamp has very short lifep which is only 1,200 hours (USAI Lighting, n.d.), it is also said to be the lamp that has the worst lifep in the world (Stouch Lighting, n.d.). With the use of LED, the user does not need to change the bulb frequently and this may reduce the maintenance cost. Frequent on and off cycling will not affect the lifep of a LED but it will affect the lifep of an incandescent lamp (Stouch Lighting, n.d.).

As there is no warm up period needed in LED, it can light up faster compared to other lamps within nanoseconds. LED is also safe to use because it is a solid-state component and does not contain glass and filament which are fragile but incandescent lamp does, so LED is more durable and difficult to damage (Singh, 2009). In addition, LED is environmental-friendly. Although both LED and incandescent lamp does not contain mercury, due to LED’s low consumption of energy, it releases lesser carbon to the atmosphere compared to incandescent lamp (USAI Lighting, n.d.). The LED’s metal components such as copper can also be recycled and reprocessed.

Moreover, LED and incandescent lamp comes in many sizes; however, LED can be extremely small (less than ) or big (Stouch Lighting, n.d.). LED can emit light of an intended colour without the colour filters because the colour of LED depends on the type of semiconductor used (Singh, 2009). Solid package of LED can be designed to focus its light, unlike incandescent and fluorescent sources that need an external reflector to collect light and direct it in a usable manner.

On the other hand, one of the disadvantages of LED is its expensive price compared to other lamps which LED costs $4 and incandescent lamp costs $1 (USAI Lighting, n.d.). LED’s performance also depends on the temperature of the operating environment. So, over-use of LED in high temperature may result in overheating in the LED package and causing the device to fail. Adequate heat-sinking is needed to reduce the temperature of LED to maintain its lifep. This is especially important for those LEDs used in automotive, medical, and military in which the device is operating in extreme temperatures and it need to have low failure rate (Singh, 2009).

Furthermore, LED must be supplied with the right amount of current to make sure that the voltage supplied is enough for the semiconductor to emit certain colour of light. It also does not approximate a “point source” like an incandescent lamp. As a result, it is difficult to use in a sector that needs spherical light (Singh, 2009).

The future of LED

LED will gradually dominate the lighting technology in the near future. As we can see, saving energy is a top priority for many people these days. Besides, taking care of the environment is a responsibility that everyone should feel accountable for. Most of us are already aware of environmentally friendly processes such as recycling to minimize the amount of waste we produce and reduce our carbon footprint. However, a lot of people are unaware of new and upcoming technologies that we can use to help reduce carbon emissions. A good example of this is LED lighting, which provides many environmental advantages. Many have realized that LEDs are today’s best option when it comes to lighting. But what might LED tech look like 5 years down the road? Or in 10 years? Here are just few reasons why we think LED will dominate the lighting technology in near future.

Assuming that, scientists have no new discovery on lighting technology that may overwhelm the advantages of LED. LEDs are now more affordable than ever. A few years ago, the price difference between CFL (compact fluorescent lamp) and LED bulbs was painfully noticeable. Today, that gap has gotten much smaller, and it will continue to shrink as demand for LEDs grow. Just to give you an idea as to how popular this revolutionary lighting technology has started in 2014 in which the LED lights only contributed to 3 percent of installations. In 2016, this percentage jumped to just over 12 percent. In 2018, we are betting these numbers will be even higher (ProGrowTech, 2018). In addition, LEDs were adopted into mainstream use quickly and they are more success by comparing to other eco-friendly technology, such as hybrid cars and solar energy.

On top of that, we are now facing a more crowded world with less resources. This lead to a serious concerns regarding providing enough water and food to support projected populations. That is where LED lights play a tremendously important role by providing enough light to sustain high-quality crops in indoor facilities. LED lights are able to adjust how quickly a plant grows, how it produces fruit or flower, and even encourage the development of nutrients. This adaptability makes LEDs one of the most valuable investments for anyone involved in agriculture (ProGrowTech, 2018). In addition, LED lights require less energy and run cooler than their counterparts. As an obvious result, we will be saving money on both electricity and water.

Nowadays, climate change has been the biggest challenge facing by the next generation of agriculturalists which is unpredictable weather. This means harvests may be hard to predict. A surprise frost and intense heat can ruin months of labor. That is why many growers are turning to indoor facilities. Of course, one of the first things missing in an indoor grow is sunlight. This is why an inevitable LED comes in as shown in. LEDs are the closest replica to natural sunlight as they are able to be adjusted to mimic minute shifts in outdoor light as shown in Figure 10, and replicate the full light spectrum (ProGrowTech, 2018). LEDs put the power back into the hands of the horticulturalist.

LED lights will also be a consideration for future lighting technology in health sector. This is because LED technology has been penetrating due to its ability to generate a clean, bright light and appropriate color to needed to assist diagnosis and treatment as shown in Figure 11. LEDs are also used in healthcare institutions to create a tranquil environment (ShineLong Technology Corp., 2018). This is because the modern LED technology produces less heat and can help controlling facility temperature and lowering lighting fixture count while reducing the need for overhead lighting. Assuming a proper lighting design of LED in the near future can help create a better environment for people who are having a tendency to headaches. LEDs paired with lighting controls can provide the ability to customize and set individual light levels in order to help improving comfort levels and confront light sensitivity (“4 major health benefits of LED lighting”, 2018). The use of LED lighting has significantly helped the healthcare sector to significantly cut down energy cost.

Smart lighting is soon to replace the whole of the lighting sector. Be it for household lighting, outdoor lighting, or even automotive lighting, smart lighting is going to be the trend of modern lighting. But why only LED? Unlike the incandescent lamps, LEDs can be switched on or off without the fear of it burning out. Fluorescent lamps on the other hand contains toxic materials such as mercury in it. It is more dangerous to operate this lamp than a LED. In addition, it is also prone to burning out similar to incandescent lamps. In order for smart lighting to become a reality, engineers have developed LED drivers. This device allows users to adjust the current and voltage input of a LED light bulb. Not only does this device permit users to alter the brightness of their lights to their preferences, it also allows users to switch between light colors since different current flow gives out different wave colors. For the automotive industry, automobiles are granted with the ability to adjust brightness of headlamps. For example, a driver can increase the brightness of the headlamps in order to have better sight on the road ahead. The driver can also reduce the brightness of the LED headlamp to avoid blinding oncoming traffic.

LEDs continue to get brighter, more efficient and cheaper. Some predict a 2 or 3 times improvement in efficiency and brightness before the decade is over with significant price decreases (“What’s new in LED Technology?”, 2018). The truth is that millions of dollars are being invested in this technology every year whether these predictions are true or not remains to be unseen in order to ensure a bright future for LED technology.

Summary

In conclusion, LEDs were used as indicator lights and calculator displays before the first bright blue light emitting diode was developed by Shuji Nakamura of Nichia Corporation in 1993. Light-emitting diode is an electrical component that is able to generate light in the visible, infrared, and ultraviolet spectre when connected to a direct current (DC). Today, LED bulbs costs 85% less compared to the first appearance of LED on the market for commercial use in the early 2000s. LED bulbs now have been a favoured choice of lighting in homes, offices, businesses, and also public places.

A light-emitting diode is a p-n junction that emits light. In order for these diodes to conduct electricity, the material in its original state has to undergo a process called doping which introduces impurities into the material. When the diode is forward biased, energy in the form of photon is released as the electrons and holes are recombined. This phenomenon known as electroluminescence happens because the electrons which jump from one band to another band will emit the electromagnetic energy in the form of photons. In order to obtain different colour from the LED, different combinations of semiconductor materials are used to vary the band gap energy of the p-n junction.

Apart from LED, incandescent lamp is one of the light sources developed by Thomas Edison in the late 1800s and it emits light by heating the filament to an extremely high temperature. Over the years, incandescent lamp has been replaced by CFL and even LED due to its energy-inefficiency. LED has an average lifep 40 times more than the lifep of an incandescent lamp. Heat emitted by incandescent lamp is relatively high when compared to LED because it needs to heat up the filament in order to generate light. Power used by an incandescent lamp is also 10 times higher than a LED which only needs 6 to 8 watts. Using LED will also reduce the cost for electricity as it only required 339kWh/year which is 10 times lower than an incandescent lamp needs. To sum up, the usage of LED has become more and more significant for our daily lives as LED provides countless benefits than an incandescent lamp.

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