How to Connect LED Modules into AC Network

In my earlier post I went through the procedure of how to physically connect a single LED component into an AC network. The connection was made between COB LED and the LED driver. When connecting LED modules (LED diodes assembled on the PCB board) you do it pretty much the same way with slight differences.

Connecting an SMD LED module into the AC network

As with a COB LED component, you will need a suitable driver for your module (see: how to choose a constant current LED driver).  You connect the positive terminals and the negative terminals of the LED driver and the LED module together to create a closed electrical circuit.

The difference to connecting a single LED component is that you may have to connect several LED modules into the same LED driver. In such case, you have to use series connection. This means that you still have to create a closed electrical circuit formed by the LED driver and these LED modules on the secondary side. You arrange the primary side like you would with single LED components. On the secondary size you connect the positive terminal of the first LED module (leftmost module in Figure 1) into the positive terminal of the LED driver. Then you connect the negative terminal of the last module (rightmost module in Figure 1) to the negative terminal of the LED driver. See Figure 1 below that shows all connections between the components.

Figure 1. Connection of LED modules into AC network through the driver.

How do you make other connections? Series connection means that you always connect the negative terminal of the previous array to the positive terminal of the following array in the chain. See again Figure 1. The output voltage of your LED driver defines how many LED modules you can drive with one driver. In case of Figure 1, one LED driver drives three LED modules. If voltage over LED module is for example 12V, the output voltage of the LED driver should exceed 36V. In the real world, you have to take into account tolerances. So in this case, 40V can be used as target for the driver maximum output voltage.

In the same way, you can connect multiple COB LEDs in series. This may be the case when you need vast amount of light.

How to actually do it?

As for physical connections of SMD LED modules, there are four options:

  1. PCB terminal block connectors
  2. Soldering
  3. Wire-to-board connectors
  4. Board-to-board connectors

PCB terminal block connectors are quite popular. They are soldered on the PCB board in the reflow process (in reflow oven) after the assembly process. You push the wires into those PCB terminal blocks in the same way as you would push the wires into the push-in terminals of solderless connectors in the single COB case.

Figure 2. PCB terminal block connector (2-pole)

Soldering is an option, if there are separate soldering pads reserved on the PCB to solder the wire(s) with tin. Soldering is usually a more cost effective option.

The numbers 3 and 4 are the special cases when you wish to interconnect two modules with each other. I’ll skip them for now and save them for later post.

If you’re interested in aLED’s new, improved LED modules, read more over here.

Feel free to drop a comment if you have questions on this topic.

How to Connect a Single LED Component into AC Network

I have two blog posts for you focused on how you connect COB LED components into the electrical network. I mean, when you have either a single COB LED or an LED module based on SMD LED components assembled on a PCB board.

Compared to traditional lighting, connecting LEDs to the electrical network is a whole new world. LEDs need direct current (DC) to light them, alternating current (AC) will not work. There are also AC modules available but those are not covered here.

In this post I will concentrate on connecting single COB LEDs. In case you are interested in connecting LED modules, I will write about that in my next post.

LED driver

You will need an LED driver, which is actually an AC/DC converter. It converts the AC voltage/current of the electrical network into the suitable DC voltage/current needed by the LED component. You will find the requirements of the LED from a datasheet provided by the manufacturer. If you need help in choosing a driver, you can read our guide.

Figure 1. Example of an AC/DC converter, LED driver. This one is from ELT with dipswitches, which means that you can choose the driving current.

Connecting COB LED into the AC network

In case of COB, you will have to create a closed electrical circuit so that the electrical current can flow through the LED component. A COB LED is basically a diode in its electrical nature: the current can flow only in a forward mode. This means that you must connect the positive (+) solder pad of the COB LED into the positive terminal of the LED driver. In the same way, you connect the negative (-) solder pad of the COB LED into the negative terminal of the LED driver. See the Figure 2 below.

 

This way, you create the closed electrical circuit that is needed to feed current through the LED so that it gives light. This closed electrical circuit formed by the LED driver and the COB LED is called the secondary side of the LED driver. LED driver feeds the power and current into the closed electrical circuit, and thus through COB LED, on the secondary side.

 

Figure 2. COB-AC Network

 

On the primary side, the LED driver gets electrical power from electrical network, AC network. The terminals of the LED driver on the primary side are called line and neutral. They are connected into the line and neutral connections of the AC network. If you have an LED driver with cables, they are usually blue (neutral) and brown (line). Some drivers also have a ground terminal, which is usually connected to the luminaire body with grounding wire. However, the closed electrical circuit is needed also on the primary side; between the network and the driver.

Usually, you will need to use some kind of terminal block to connect the driver into the electrical network on the primary side.

Picture of a terminal block

Figure 3. The example of terminal block to connect the LED driver into the electrical network.

Two options

Finally, as for physically connecting a COB LED into the LED driver, you have two ways to do it:

  1. solder the wires on the solder pads of the COB
  2. use solderless connectors.

In the first method, you manually solder the wire by using soldering iron with high temperature that melts the soldering material such as tin. After cooling, there is a joint between the wire and the COB solder pad. You need two wires, one for plus and one for minus solder pad.

In the second method, you use a solderless connector.

Figure 4. The solderless connector.

The solderless connector does the same effect as the soldered wire. You need the electrical connection also in this method, but you won’t need to solder the wire by melting tin. You just push the wire into the push-in terminals of the connector. Again, positive to positive and negative to negative terminal. They are marked on the connector. Basically these push-in terminals work with a combination of metal plates and springs that then make the connection to the solder pad of the COB LED.

The difference between these methods is, that unlike with soldered joints, in the solderless connector method the springs may loosen a bit over time and loss of contact may occur. Solderless connectors are generally thought to be more expensive than manual soldering.  

In my next post I will go through the steps for connecting LED modules.

Thank You for Everyone at Elfack 2017

I would like to thank everyone who we met at the Elfack Exhibition in Gothenburg, Sweden.

We had some good conversations with our existing customers as well as new people. This year we tested the color quality of Citizen’s LEDs at our stand. We got many answers through our questionnaire and found out that many visitors were excited about this new way of lighting.

If you took part in the test, you will receive the test results soon. We will also share these results with the public a little later.

We had a chance to show you our new products and the feedback we got from you was very encouraging.  I went through all the products in my last blog post, and if you wish to download more information about them, you are most welcome to do so here.

The products displayed at Elfack include:

  • aLED Engine
  • Citizen Gen 6
  • AC COB
  • Citizen Vivid Series
  • Furukawa Heatpipe
  • Merrytek sensors
  • Letaron & aLED Drivers

Our personnel will contact you as agreed, if they haven’t already. In case you have anything to ask, you can contact us directly.

 

What We Are Presenting in Elfack?

Elfack exhibition will be held in Gothenburg, Sweden from 9th to 12th of May. As it has been with previous exhibitions, we will be releasing new products and presenting the latest technology at our stand.

This year we will introduce and present the following products at our stand F04:70.

aLED Engine

aLED Engine

aLED Light Engine

We designed aLED Engine for applications that require a lot of light. aLED Engine consists of Furukawa heat pipe and Citizen COB LED.

In addition you can also choose a suitable optics and LED driver for the light engine from our selection. Suitable drivers are available as on/off, 1-10V dimming and DALI dimming.

aLED Engine is also compatible with Merrytek sensors, which allow you to control the lighting as you wish.

The 300W engine produces 36.000 lm at 4.000K and weighs only 3,6 kg with a driver installed.

aLED Engine will be at our stand in Elfack. There you can see the engine in action and try it with a daylight sensor.

Download More Information

Furukawa HYC Series

Furukawa HYC Series uses heat pipe technology to transfer the heat and makes heat sinks more efficient in cooling the LED.

how heat pipe works

How Heat Pipe Works

Heat Pipe’s thermal conductivity is almost 200 times better compared to copper. This allows the heat sink to be a lot smaller than we are used to.

Smaller heat sink reduces the weight of the luminaire dramatically.

The heat pipes effectively transfer heat from the heat source throughout the whole heat sink cooling the heat source faster than ever.

Heat Pipe vs. No Heat Pipe

Heat Pipe vs. No Heat Pipe

Furukawa heat pipes are compatible with Citizen COBs.

Furukawa heat pipes will be at our stand so you can see and try how light they are.

Read more about Furukawa heatpipe from here.

aLED & Letaron Drivers

aLED Driver

aLED Driver

aLED and Letaron offer a versatile range of both constant current and constant voltage drivers from low to high power (from 1 W up to 600 W).

Ouw own aLED drivers are best suited for high power applications. They are all available in IP68 and can be ordered as on/off, 1-10V dimming or DALI dimming.

Letaron drivers are best suited for low power applications, although they are available up to 52W.

Letaron offers a variety of designs to suit your needs including round, rectangular and slim models.

The Letaron low power drivers are also compatible with OLED light sources.

aLED and Letaron drivers will be on at our stand so you can see and try them yourself.

Merrytek

Merrytek sensors

Merrytek offers a wide range of different sensors. Some sensors come with LED driver and some are independent and can be connected to LED driver.

Merreytek has products particularly designed for eg. homes, schools, stairways, warehouses, offices, parking garages and outdoor use.

Merrytek’s intelligent lighting control products include:

  • Microwave motion and daylight sensors
  • Dimmable LED drivers
  • LED drivers with intergrated sensors

There will be Merrytek products on display at our stand. We will have an aLED engine wiht Merrytek’s daylight sensor on our stand, so you can see how it functions.

Citizen Gen 6, AC COB &Vivid Series

Citizen released Gen 6 COB and AC COB earlier this year with improvements compared to the previous versions.

Thermal Resistance

Thanks to better heat resistance, you can use much smaller heat sink. Gen 4 on the left, Gen 5 on the middle and Gen 6 on the right.

For the new Vivid series we’ve prepared a demo wall at Elfack for you to examine the possibilities of color quality control in LED lighting.

Seminar about color quality

We will organize a seminar about color quality on the first day of the exhibition.

Color comparison Vivid COBColor Comparison Regular COB 3000K Ra80 vs. Vivid Brilliant

The seminar will take place on Tuesday 9th of May.
Time: 16:00-19:00
Place: Hotel Gothia Towers, Tower 1, meeting room R22-23

The program:

  • Doors open at 16:00
  • Coffee
  • Welcome / Arrant Light Oy by Janne Mäkinen, Managing Director / Arrant-Light Oy
  • Color Quality with CITIZEN by Kosuke Tsuchiya, Field Application Engineer / Citizen Electronics Co.
  • Demonstration and open discussion
  • Refreshments and snacks
  • Close at 19:00

Please sign up for the seminar as soon as possible or latest by April 30th. We have limited seats and there is room for the first 20 persons only.

Sign Up for Our Seminar

Welcome to visit our stand F04.70 at Elfack.

All datasheets and other material will be available from our website soon. If you wish to download material about these new products before the exhibition. You can do that here.

AC COB – Easier way to make a luminaire

What is AC COB?

AC COB is brand new AC LED solution from Citizen Electronics. It is available with holder which contains necessary components to connect package directly to mains voltage. So basically it is designed to make life of luminaire manufacturer easier.

AC COB With Connector

AC COB With Connector

What advantages?

AC COB has integrated circuit which allows you to control luminous flux more accurately. For all CCT and CRI versions you are able to have exactly same luminous flux from the package e.g. 750, 1000, 1500 and 2000 lumens.

5 volt output enables you to use e.g. motion sensor, so you can easily adapt external sensors to easily add features to your luminaire.

There is no additional losses from driver and so there is no problem to have good efficacy even with low powers. AC COB with new integrated circuit has good compatibility with dimmers, you are able to dim this solution with Triac (leading-edge) and Transistor (trailing-edge) dimmers.

Small form factor and no need for external driver allow even more creativity to luminaire design. There is no need to worry where to place the driver.

What you need to take to consideration?

AC COB has of course similar characteristics than normal COB meaning warmer CCTs have lower efficacy than cooler CCTs. With fixed luminous flux, that means you have difference in power. So 2700K Ra90 AC COB consumes more power than 5000K Ra80.

And of course AC is still AC. If you don’t use more complex circuitry to modify AC to DC, you will still have AC characteristics affecting luminous flux. Mainly with AC LEDs this means that you have flicker present in light source. To reduce that effect, it is good to consider e.g. secondary optics which lower this phenomenon.

AC COB In Connector

AC COB In Connector

Conclusion

Even though AC LED might have it’s limitations it has certainly some advantages which make it viable solution as light source. It has ENEC certified components which are easy to use to design new luminaires and you can make testing with this solution in different luminaires. Now it is time to consider where you could use AC COB to realize its advantages.

You can download datasheets and brochure from the button below.

Download Here
Citizen COB lineup

Citizen COB LEDs generation 6 – What is new?

Citizen have released generation 6 from their successful series of Citizen COB LEDs. In this post I’ll go briefly through, what is new and what advantages these COBs have compared to previous generations.

There are five main points at generation 6 from Citizen:

1. Performance increase

Performance will up to 7% depending on CRI of LEDs. There will be also slight decrease on forward voltage, which increases lm/W efficacy on LEDs.

2. MacAdam 2-step option

MacAdam 2-step binning will be an option in new generation. Although we have had very tight 3-step binning already, there is now option to order also 2-step versions of COBs. So if you desire to have 2-step SDCM COBs in your products, we have now solution for that.

3.Thermal resistance decrease

Thermal resistance is further decreased from generation 5. Decrease from generation 5 is 5% and from generation 4 even 38,5%. This allows you to minimize your need for heat dissipation. Another option is that you can create new, bigger lumen categories with your existing products.

Thermal Resistance

On the left a heat sink needed for COB Gen 4 LED. On the middle heat sink needed for gen 5 LED. On the right, heat sink needed for COB gen 6 LED. The power of the LED is same in every case.

4. Increase of maximum Tc

Maximum Tc-temperature has been set to 120 degC. Allowable Tc-temperature will rise from 105 degC to 120 degC. This will help you to maximize light output from your design, so you can use smaller heat sinks to get more light.

5. Increase of maximum Tj

You will be allowed to have higher Tj-temperature than in previous generations, so maximum Tj-temperature will be now 150 degC. This will give you wider LED driving options especially with bigger COB packages.

Citizen COB LEDs continue to increase their performance and offer amazing coverage for lumen packages. Packages range from under 100 lumens up to 60 000 lumens from single light source. If you haven’t yet tried Citizen COB LEDs, now it is good time to learn why Citizen has been top player in the industry for so long time.

You can download the whole catalogue, datasheets and simulator tool for Generation 6 COBs from our website.

Download Catalogue, Gen 6 Datasheets and Simulator Now

Glass Lens vs. Silicone Lens in Street Light

What is the difference between a lens made from optical glass and the lens made from silicon, when used in street light application?

In this blog post, I will explain the pros and cons of both lenses. I will also use a case example to showcase the differences.

The Basics

First let me explain few basic terms related to optics in street light:

Light Pollution

Light that doesn’t go to desired direction and causes harm of anykind. It is wasted light, that isn’t used to its primary purpose. Light pollution can be divided to three different categories:

  • Glare

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Discomfort glare results in an instinctive desire to look away from a bright light source or difficulty in seeing a task. So as told by its name, discomfort glare causes discomfort.

  • Uplight
Light Pollution (Uplight/Skyglow)

Light Pollution (Uplight/Skyglow)

Uplight can be seen especially in cities: it makes sky glow and stars disappear.

  • Light tresspass
Light Pollution (Light trespass)

Light Pollution (Light trespass)

Light trespass is found in the vicinity of streets: it can prevent you from sleeping or disturb your garden lighting.

Optical glass

Pros:

  • Cheap to manufacture
  • Very high temperature range, sensitive also to stress

Cons:

    • Complex optical shapes can’t be done accurately or if the complex shapes are needed, it is expensive
    • Non-optimal light distribution in street light
    • Heavier than silicone (freight costs are more expensive)
    • Lower light transmission than in silicone lenses

 

Silicone

Pros:

  • Enables high precision manufacturing of complex optical shapes
  • High integration level in luminaire
  • Material weighs less than in case of glass lens

Cons:

  • Cost is higher than for glass lens

  • Lower temperature range
  • Lower fire rating

Glass Lens

Glass Lens Light Distribution in Street Light Application

Glass Lens Light Distribution in Street Light Application

In the image you can see the light distribution image taken from above. This application uses Glass lens.

      • Boom angle 15 deg
      • 10880 LED lm, eff 88%
      • Eav 9.0 lx (>9.0 lx)
      • Eav/Emin 2.2 (<4.0)
      • Lv max/Lav 0.3 (<0.4)

Silicone Lens

Silicone Lens (Stella DWC2) Light Distribution in Street Light Application

Silicone Lens (Stella DWC2) Light Distribution in Street Light Application

In the image you can see the light distribution image taken from above. This application uses Stella DWC2 Silicone lens.

      • Boom angle 10 deg
      • 8400 LED lm, eff 92%
      • Eav 9.0 lx (>9.0 lx)
      • Eav/Emin 2.3 (<4.0)
      • Lv max/Lav 0.3 (<0.4)

Results

Glass lens needs more lumens for the same application. In this case, around 20% more. This means that you generally speaking need more power to get the same amount of light out from the luminaire.

The reason behind the lumen need is the fact that glass lens generates more light pollution. You can see that the trespass light area is much larger in glass lens image (the red box). And on top of this, glass lens distributes light 10 meters away from road. In comparison, silicone lens only distributes 7 meters.

So I think I can end this blog post by stating that the silicone lens gives a lot of advantages over glass lens in street light application.

Vivid LEDs: Special Color Rendering With Spectrum Tuning

When we talk about color rendering, traditionally that conversation has been filled with CRIs and Ra-indexes. These traditional ways of telling how well certain light source represents sunlight have been criticised because they may not tell the whole truth.

In recent years, LED manufacturers have been trying to answer this criticism by creating different products. Terms like “premium white”, “crispy white”, “pearl white” and “vivid white” have come to LED markets.

Despite the different terms, they are all meant for the same purpose: To represent certain colors and make the lighting look better. I will be using term “Vivid” as it is the term Citizen Electronics uses. And to be honest, it describes the purpose of these LEDs quite well.

Color rendering

Color rendering means simply how well a white light source can show, or render, the true colors of different physical objects compared to sunlight. You know the effect when you buy a jacket in the clothes shop and it looks completely different in sunlight.

Colors are divided into 15 indexes (R1-R15). A general color rendering index (CRI or Ra-index) is defined as an average of the sum of first eight indexes (R1..R8). However, these first 8 indexes are rather less saturated colors, while indexes R9-R12 represent highly saturated colors (red, yellow, green, blue).

CRI 100 = Sunlight

For example, in grocery stores, a shopkeeper may want to highlight red color of meat or colors of vegetables. This means that the general color rendering index doesn’t really tell anything about the rendering capabilites of the light. In this case, high rendering index of some of R9-R12 indexes is necessary. It doesn’t matter how high the CRI is, R9-R12 can be anything.

CRI 83 (look at R9)

CRI 83 (look at R9)

The above image shows the index values of R1-R15. The CRI is 83, but look at the R9 value. Not very good.

So basically, the LED itself can have the CRI of 97 and you still have no idea how does it render red or green for example.

Vivid via Spectrum tuning

Vivid LEDs are made using spectrum tuning. In short, this means that the phosphorus of the LED has been modified. How it is modified, depends on the LED and the intended application. Note that spectrum tuning can be made also by using RGB-LEDs.

For example, Vivid White LED’s spectrum has been tuned so that it represents white and bright colors as well as possible. The colors are more saturated than under typical normal LED light.

Test report on Vivid White aLED Module

Test report on Vivid White aLED Module. Click the image to open it in new tab for better view.

These LEDs work very well for example, in clothing stores, where you have a lot of different colors that need to look good.

Here are two good principals when choosing LED:

  1. Think about your application, what colors do you want to highlight?
  2. Don’t stare at the CRI (unless you get a full report), it might not tell everything

Conclusion

Traditional way of thinking color rendering solely through the CRI should be updated. More importantly, you should know what you want to highlight and ask for a LED suited for your application.

Download More Information About Vivid

 

How to use Citizen LED simulator

Datasheets are essential part when you compare how different light sources work in your solution. Usually it can be time taking and exhausting to glance at datasheet and find values you are looking for. This gets even harder if you have multiple LEDs or different LED packages, which would mean that you have look at multiple datasheets to get different values.

This is the reason why Citizen has created a Citizen LED simulator. The simulator is very easy to use and makes comparing different LED packages a lot easier. If you haven’t yet tried it or you don’t have the simulator, you can download it for free from our website.

Citizen LED simulator basic view

Citizen LED simulator basic view.

The steps

Follow these steps to use the simulator.

You can choose desired CCT and Ra and selection simulator shows packages and product codes of existing products.

You can choose desired CCT and Ra and selection simulator shows packages and product codes of existing products.

  1. Select the CCT and Ra

First you need to select desired CCT and Ra from condition input field.

You can choose desired CCT and Ra and the selection simulator shows packages and product codes of existing products.

  1. Choose whether you want to search based on the desired lumen amount or driving current

After you have selected color temperature and CRI value, you can choose between driving current (forward current in simulator) or desired luminous flux.

  1. Input the Tc-temperature

Then you can input Tc-temperature. If you have no idea how much Tc is or would be in your solution, values around 60 degrees are realistic to use as many light sources reach temperatures close to that while being used.

Example

In this example, I have chosen that I want my LED to be 4000K, Ra80 Min. And I want to see what options we have to get around 3000 lumens out from luminaire. Luminaire optics etc. will drain around 300-400 lumens in my solution. So I have determined that I need 3400 warm lumens from LED and estimated that Tc-temperature is 60 degrees.

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I can see that I have ten different LED packages I can get the 3400 lumens from. In first column after product code you can see what current you should use to get these values. If you don’t have LED driver, in which you can choose output current, it is recommended to then select current value you have LED drivers available in. In this case, 700mA seems to be a good choice as many of the LED’s have driving current close to that.

So I change “forward current” instead of “luminous flux” from the condition input and insert 700mA.

LED packages which give you desired lumens with 700mA. We still have six options to choose from.

LED packages which give you desired lumens with 700mA. We still have six options to choose from.

This will give me a list of LEDs I can use with 700mA driver. And more importantly give me a good overview of LED packages that can give me my desired lumen amount. If you have problem that you can’t find driver with suitable current, you can contact me for help.

In this case, CLU028-1204 would suit my lumen need quite nicely and CLU048-1212, would probably be an overkill for this application. All the other options, might suit my solution although they give roughly 10% more lumens. Whether this is ok, depends really on my application and desired efficacy.

Other applications

Citizen LED simulator is also powerful tool to use when you want to see easily how much lumens you get when driving LED with different currents. Good example is that if you have LED driver which has different current options and flexible LED package, you can use only two components to realize many different lumen packages.

As an example I did this exercise with ELT 42W multicurrent LED-driver and Citizen CLU038-1205 LED package. This driver has option to select different driving currents with dipswitch. If we take Esko’s advice and look from driver datasheet, we can see that output voltage area is suitable from 500mA to 1000 mA.

Below you can see LED characteristics with different current. I have also added forward current column to make this table easier to read. Tc temperature is 60 degrees in all cases.

Table with CLU038-1205 4000K Ra80 LED from 500mA to 1000mA.

Table with CLU038-1205 4000K Ra80 LED from 500mA to 1000mA.

You can also use the LED simulator to estimate the amount of lumens lost due to your luminaire (optics etc.). If you measure LED Tc-point and input the driving current you use to simulator, you should have pretty good estimation that how much lumens you should get out from your luminaire.

If you find out that the loss is too big, the you can either change the LED to a different package or improve the optics of your luminaire.As you can see, you can use this driver & LED combo for a luminaire from ~2500lm to ~5000lm.

Please feel free to contact me if you have any questions.

You can download the latest simulator below.

Download COB Selection Simulator

 

What is OLED in Lighting?

OLED means Organic Light Emitting Diode.  It works in similar way than (semiconductor) LED. Both need positive and negative charge carriers to generate electrical current and finally generate light.

It is a surface light source based on organic material layers. LED, on the other hand, is a point light source that is based on semiconductor materials. But the operation is based on the same principle.

OLED as Surface Light

OLED as Surface Light

The large-area LED modules, that are covered by opal diffuser, are basically similar light sources as OLED panels. Without this diffuser, these LED modules also are point light sources because of small SMD LED diodes they have on their surface.

OLED panels are surface light sources by nature. They give uniform light.

The benefits OLED:

  • Its light has spectral power distribution very close to sunlight.
  • Color rendering index (CRI) of 90.
  • Produces no glare
  • Produces very little heat(<35°C),
  • Doesn’t produce any UV and therefore it doesn’t cause blue light hazard risk.
  • Panels are thin and lightweight.
  • Simple light: panels don’t need many accessories unlike LED, such as heat sinks, diffusers, or other optics. It only needs the power source and the light source itself.

    Spectrum of OLED

    Spectrum of OLED

Structure of OLED

The OLED structure consists of layers. These layers have different purposes.

There are basically THREE different kinds of layers that have some purpose. Of course, you need anode and cathode terminals to bring electricity from outside world to the panel. As an example, LG Display uses Aluminium as cathode material and ITO (indium tin oxide) as their anode material.

  • Light generation layer: Emissive Layer (EML). Generates light.
  • Electrical current flow guidance: Electron Transport Layer (ETL), Hole Transport Layer (HTL) and Hole Injection Layer (HIL). These layers are used to transport charge carriers in optimal way to the light generation layer, EML. But also, they have to be optically suitable for light generated in the EML layer so that as much light as possible is extracted from the panel.
  • Third type of layer: Encapsulation. The encapsulation layer is used to protect inner optically active layers from any outside harm that could deteriorate the operation of the panel.

This kind of set of layers is called a stack.On top of the stack is the encapsulation layer.

OLED Structure

OLED Structure

For example, LG Display uses two-stack structure for 3000K and 4000K OLED panels and three-stack structure for 2700K panels. Because there are more stacks in 2700K version, the overall voltage over the panel is a bit higher.

Encapsulation

One major problem with the organic materials is that they are very sensitive to oxygen and moisture. This means that OLED panels need to be protected – as even a single water or oxygen molecule can harm the panel.

The encapsulation layer also protects from minor physical impacts. If this encapsulation layer deteriorates it will affect the optical layers. Usually strong glass is used for rigid OLED panels. But flexible panel is gaining more and more popularity. Flexible panels use plastic.

 

Drawbacks

The major drawbacks of OLED panels are:

  1. Easy to break

At the moment, most panels use glass substrates. These substrates are very fragile and are easy to break when not handled with care. This will improve in future as technology develops and plastic substrates will gradually replace glass.

  1. Cold endurance

You can’t use the panels in temperature of under 0 degrees of Celsius. This will obviously place some constraints for the use.

It is very probable that the cold endurance will get better in the future as the technology develops.

  1. Technological immaturity

OLED is still very young technology and it can’t produce very large amounts of light. It also loses to LED in luminous efficacy.

This will obviously improve in the future as manufacturers are investing in new product facilities.

Applications

As a surface-type lighting element, OLED can be used in different kinds of interior designs. It can give the background or accent/ambient lighting for example some artworks or other objects.

OLED as an Accent Light

OLED as an Accent Light

Basically, new application areas are up to you.

You can find and download ideas about OLED lighting from our website.