By Owais AliReviewed by Laura ThomsonNov 6 2024
This article provides an overview of light-emitting diode (LED) technology, focusing on its efficiency, historical development, recent advancements, challenges, and prospects.
Image Credit: DKai/Shutterstock.com
Overview of LED Lightning
The efficiency of LEDs is attributed to their unique semiconductor materials and structure. Unlike incandescent bulbs, which generate light by heating a filament, LEDs directly convert electricity into light through electroluminescence. This process eliminates the energy loss associated with heat generation, ensuring a more efficient light production.
LEDs are created by joining two types of semiconductor crystals -- one doped with a 3-valent material, such as indium or boron, to form a P-type semiconductor, and the other doped with a 5-valent material, such as phosphorus or arsenic, to create an N-type semiconductor. This doping process results in a p-n junction, which only allows current to flow in one direction.
When an appropriate voltage is applied across the PN junction, electrons from the N-type region move to fill holes in the P-type region (forward bias). This recombination releases energy in the form of photons, generating light. The color of the emitted light depends on the semiconductor's energy band gap and the doping materials used; for example, adding aluminum to a gallium arsenide diode results in red LED light.1
Benefits of LED Lightning
LED lighting offers numerous advantages that have driven its rapid adoption across various applications. In a recent study, the University of Michigan researchers demonstrated that LEDs can be up to 44% more efficient than 4-foot fluorescent tubes, offering 18%-44% more efficiency than T8 fluorescent lamps.2
LEDs also boast a long lifespan of up to 25,000 hours -- 25 times longer than traditional bulbs -- significantly reducing replacement and maintenance costs. Their inherent solid-state nature ensures durability, making them resistant to breakage and capable of withstanding extreme conditions.
LEDs also provide instant brightness and versatile color options and are compatible with low-voltage systems, including solar energy, making them an ideal choice for industrial and outdoor applications.3
Historical Development of LEDs
The lighting industry entered its third revolution with the widespread adoption of LEDs, following the eras of incandescent lamps and fluorescent tubes. Advancements in electroluminescence enabled this shift, a phenomenon initially observed by Henry Joseph Round in 1907.
Subsequent breakthroughs included Oleg Losev's creation of the first LED in 1927, but it was Nick Holonyak Jr.'s development of the first practical visible-spectrum LED in 1962 at General Electric that marked the onset of LED commercialization.
Initially, LEDs were constrained by low luminous flux and monochromatic light, limiting their use in general lighting. However, Shuji Nakamura's development of the blue LED addressed these issues by enabling the creation of white light and a range of color temperatures.
By the 2000s, the commercialization of white LEDs led to their rapid adoption across various lighting applications. This trend persisted into the 2010s due to enhancements in efficiency, brightness, and cost reductions. The technology continues to evolve, improving efficiency, color quality, and application.1
Recent Research and Developments in LEDs Overcoming LED efficiency droop
A study published in Science Advances addresses the long-standing issue of efficiency droop in LED technology, where brightness decreases after a certain point despite increased electrical input.
The researchers introduced a nanoscale LED design featuring zinc oxide fins that significantly enhance electrical current handling and mitigate efficiency droop effects. This advanced LED achieved 100 to 1,000 times more brightness and generated up to 20 microwatts of power, compared to the 22 nanowatts typically produced by traditional submicron-sized LEDs.
This breakthrough represents a major advancement in LED efficiency, potentially enabling the creation of brighter and more efficient light sources for diverse applications, including communication technologies and disinfection systems.4
Quantum dot LED smart lighting system
The University of Cambridge researchers developed a quantum dot-based smart lighting system that offers superior color accuracy and broader spectrum customization compared to traditional LEDs. The results are published in Nature Communications.
The QD-LED system uses multiple primary colors beyond the standard green, red, and blue, allowing for more accurate reproduction of daylight. It achieved a correlated color temperature range from 2243K (reddish) to 9207K (bright midday sun) and a color rendering index (CRI) of 97, surpassing the 80 to 91 CRI range of current smart bulbs.
This advancement could significantly improve visual comfort and energy efficiency by offering a more dynamic and responsive lighting environment.5
Flexible organic LED mimicking candlelight
In a recent study published in ACS Applied Electronic Materials, researchers developed a flexible organic LED that emits a candlelight-like glow with reduced blue light, which can disrupt sleep by suppressing melatonin production.
This innovative LED uses a mica backing, allowing flexibility and durability, withstanding up to 50,000 bends without breaking. The light generated suppresses melatonin production by only 1.6% after 1.5 hours of exposure, compared to 29% suppression from cold-white compact fluorescent lamps.
This advancement provides a practical solution for creating comfortable nighttime lighting without interfering with sleep patterns.6
Challenges and Limitations of LED Lighting
Despite LED lighting's advantages, several challenges and limitations persist. The transition to LED technology, while offering energy efficiency, has led to various issues.
For example, in 2013, an ambitious project to replace 2,600 street lights with LEDs in Davis, California, faced significant issues, including excessive glare, light intrusion into homes, and a shift in the town's nighttime ambiance. In response, the city adjusted the project to use lower color temperature lights at an additional cost of $350,000, highlighting the need for careful planning to balance human comfort and aesthetic considerations when transitioning to LED lighting.
While LEDs are energy-efficient, their blue light content can disrupt circadian rhythms and suppress melatonin production, affecting sleep patterns. This has been noted across Europe, where the switch from sodium to LED lighting has increased blue light exposure, impacting human health and the visibility of stars.
The increased brightness from LED lighting disrupts natural light/dark cycles, affecting animal behavior such as migration and reproduction. For example, artificial light can confuse migratory birds and sea turtles, leading to harmful consequences for these species.7,8,9
Read More: How Does Light Pollution Affect Birds? The Future of LED Technology
LED lighting technology has come a long way since its inception, offering significant benefits in energy efficiency, longevity, and versatility.
Ongoing research is focused on maximizing LED efficiency to approach theoretical limits, which promises further energy savings and a reduced environmental footprint. Integrating LEDs with advanced control systems and IoT technology is expected to enhance lighting management by optimizing energy use and customizing lighting experiences.
With growing environmental concerns, there will be a stronger emphasis on sustainable manufacturing practices and materials, including research into organic and biodegradable options for more eco-friendly lighting solutions.
While LEDs are set to play a pivotal role in advancing efficient and sustainable lighting, evaluating their environmental impact and ensuring their safety for wildlife and ecosystems will be essential.10
References and Further Reading Montoya, F. G., Peña-García, A., Juaidi, A., & Manzano-Agugliaro, F. (2017). Indoor lighting techniques: An overview of evolution and new trends for energy saving. Energy and buildings, 140, 50-60. https://doi.org/10.1016/j.enbuild.2017.01.028 Liu, L., Keoleian, G. A., & Lewis, G. M. (2024). Life cycle cost analysis of LED retrofit and luminaire replacements for four-foot T8 troffers. Lighting Research & Technology, 56(4), 403-420. https://doi.org/10.1177/14771535231207810 Indiana University of Pennsylvania. (2024). LED Lighting Benefits. Available from: https://www.iup.edu/energymanagement/howto/led-lighting-benefits.html Nikoobakht, B., Hansen, R. P., Zong, Y., Agrawal, A., Shur, M., & Tersoff, J. (2020). High-brightness lasing at submicrometer enabled by droop-free fin light-emitting diodes (LEDs). Science Advances, 6(33), eaba4346. https://doi.org/10.1126/sciadv.aba4346 Samarakoon, C., Choi, H.W., Lee, S. et al. (2022). Optoelectronic system and device integration for quantum-dot light-emitting diode white lighting with computational design framework. Nat Commun 13, 4189. https://doi.org/10.1038/s41467-022-31853-9 Chen, T. H., Chen, H. J., Weng, C. Y., Chen, F. R., Liou, D. S., Chen, S. Z., ... & Jou, J. H. (2022). Flexible Candlelight Organic LED on Mica. ACS Applied Electronic Materials, 4(5), 2298-2305. https://doi.org/10.1021/acsaelm.2c00123 Faraudo, F. (2024). How a California Community Was Blindsided by LED Lighting Problems. Available from: https://propmodo.com/how-a-california-community-was-blindsided-by-led-lighting-problems/ Mohamed, W. (2022). Increase in LED lighting 'risks harming human and animal health.' Available from: https://www.theguardian.com/environment/2022/sep/14/increase-in-led-lighting-risks-harming-human-and-animal-health Garza, S. (2023). Can Turning Off the Lights Save a Sea Turtle? Available from: https://blog.nwf.org/2023/05/can-turning-off-the-lights-save-a-sea-turtle/ Faraudo, F. (2024). To Get the Most Out of LED Lights They Need to Be Smart. Available from: https://propmodo.com/to-get-the-most-out-led-lights-they-need-to-be-smart/
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