I’m sure you’ve heard of the phrase “nothing lasts forever,” but how true is this for LEDs?
When it comes to traditional bulbs, light is produced by heating a filament. Over time this filament gets hotter and weaker, eventually causing it to snap.
But LEDs do not contain a filament, and instead, generate light using a semiconductor.
If LEDs do not burn out like traditional bulbs, then why do they stop working? What is it about this new technology that allows LEDs to last?
LED bulbs will get progressively dimmer throughout their life until they stop producing light altogether due to lumen degradation. Most LEDs have an L70 rating, which denotes how many hours the bulb will last before it hits 70% of its initial light offering.
At one end of the scale, a 50,000 hour LED can be left on 24/7 for six years before it needs replacing. As well as being more energy-efficient and reliable, I’m sure you can see that LEDs are an extremely long-lasting solution.
If you’re interested in the physics behind LED deterioration, then you’ll want to keep reading. In this blog post I’ll be covering:
Why Do LED Bulbs Lose Their Brightness Over Time?
An interesting fact that I learned recently is that after the age of 60, human vision deteriorates faster than LED bulbs. This helps to contextualize just how slowly LED bulbs fade.
In the U.S, most LEDs are given an L70 rating, this sets out how long it will take for lumen output to fall below 70%.
Though L50, L80, and L90 ratings are also used, L70 is the most common as this is when light becomes noticeably different.
According to the Alliance for Solid-State Illumination, the human eye only detects loss of brightness after 20%.
Once an LED has faded past 70%, it will still emit light, but it may no longer be fit for purpose.
Furthermore, lumen degradation is not linear, and though it may begin slowly, after 70%, the light will fade faster and faster.
But why exactly does this happen? Let’s delve a little deeper into the construction of LEDs.
Most LEDs generate light using a semiconductor made from Gallium Nitride (InGaN). During the manufacturing process, threading dislocations occur in this Gallium Nitride.
These anomalous dislocations disrupt the structure of the semiconductor.
Threading dislocations are bad primarily because the positive and negative electrons can still meet, but they do not create light.
This harms the semiconductors quantum efficiency, which is the percentage of electron-hole combinations.
So right from the manufacturing stage, there are parts of the semiconductor that cannot emit light.
What’s more, these dislocations gradually get worse, and over time more dislocations are introduced. This means that quantum efficiency, and therefore light output, gradually declines with age.
Do LED Lights Dimmer When They Are Hot?
With that in mind, you may be thinking, “how can I slow down or prevent threading dislocations?” Fortunately, the answer is simple: keep your LEDs cool.
I can’t stress it enough.
Heat is the enemy of LEDs, and excessive heat has short-term and long-term implications on a bulb’s lifespan.
Most LEDs contain a heat sink that dissipates heat away from the diode to prevent overheating.
But beyond this, if you want to keep your LEDs in tiptop shape, it’s recommended that you don’t let the ambient temperature exceed 140°F (60°C).
In the short term, excessive heat can lead to a reduction in light output and color changes.
This is because heat causes the internal components of the bulb to malfunction.
In fact, there is a negative correlation between heat and lumen output – as the temperature of a bulb increases, its lumen output decreases.
In addition to this, the temperature to which an LED is subjected can impact its life expectancy.
Excessive heat and insufficient cooling accelerate the formation of threading dislocations. As you know, threading dislocations have a direct impact on lumen output.
So hotter semiconductors will experience faster lumen degradation.
Has My LED Light Reached The End Of Lifespan?
It’s worth bearing in mind that a dim bulb doesn’t always mean that your LED has reached the end of its lifespan, there may be other reasons why your bulb is acting up.
The easiest way to check whether your LED has reached its end of life is by trying it in a different fixture.
If the dullness improves, the problem is related to another part of the circuit. But if the bulb does not get brighter, it’s probably time to replace it.
One of the most common reasons for low lumen output is an incompatible dimmer switch.
LEDs can work on a dimmer, but they have to be designed for this purpose.
Most standard LEDs do not have the requisite dimming components, so you need to ensure that your LEDs can be dimmed.
Furthermore, your LED has to be connected to an LED compatible dimmer switch.
LEDs operate at a much lower voltage than traditional bulbs, so most ‘universal’ dimming switches will be inadequate.
Alternatively, your LEDs could be dull because of a lousy connection restricting the voltage your bulb receives.
There are several causes of this: the contact point could have corroded, there may be a loose wire, the bulb may be too loose in the socket, or it may have been screwed in too tightly.
If you’re confident with electronics, it may be useful to open the LED up and eliminate these potential problems one-by-one.
How To Reduce Degradation Over Time?
As I’ve already mentioned, the primary cause of LED degradation is excess heat.
Therefore, it follows that the best way to combat this is by keeping your bulbs cool and not allowing them to overheat.
White LEDs are particularly susceptible to heat damage. Excess heat breaks down the phosphor coating inside the bulb that generates white light.
Degradation is not impacted by the number of times LEDs are switched on and off.
It’s also good practice to minimize the level of vibration that LEDs are subjected to.
In this regard, LEDs are more durable than traditional bulbs. However, their internal components can still be disturbed by too much movement.
To protect your bulb from excess vibrations, make sure it is in a secure fitting away from ceiling fans and doors.
If you need a long-lasting lighting solution and reduces the amount of waste you produce, LEDs are the answer.
Providing they’re correctly installed and looked after, with LEDs, you’ll never have to worry about them randomly dying.
In recent years the Cree company has taken steps to counteract lumen degradation by implementing a component into their bulbs that continuously measures light output.
So it seems that as technology advances, lumen degradation in LEDs may become a thing of the past.
Have you ever noticed LEDs in your home becoming duller? How long have you had them?
Write your answer in the comments section below, it would be great to hear from you!