Monthly Archives: June 2016

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.


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.



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.


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.


FAQ: OLED – Panels

From this post, you can find the most frequently asked questions related to OLED panels. The post will be updated in the future if new questions arise.

Q: What is OLED? Does it work in the same way as LED?

A: 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.

OLED Structure


You can read about the structure and tehnology of OLED from my other blog post.

Q: How OLED panel is attached on the surface/profile that is used in the luminaire?

A: The panel can be attached in many ways, but most common way  is to use adhesives. The screw connection is not recommended for panels.

Every panel manufacturer should have a list of adhesives that are not allowed with their products.

Q: How the to handle OLED panels?

A: You must handle them with care. At the moment most panels use glass substrates and because the panels are very thin, they break very easily. In the future, plastic substrates will replace the glass substrates. This will obviously decrease the risk of breaking the panel.

You can find more exact instructions on handling the panel from the datasheet of the panel.

Q: Can you bend the OLED panel because it is so thin?

Bendable OLED Panel in Luminaire

Bendable Panel in Luminaire

A: You can’t bend the glass substrate panels.

Plastic panels are ok to bend. There is a limited bending radius that can be found from the datasheet. Within that limit, you can bend the plastic panels almost endlessly.

Q: How you connect the OLED panels if you want to light many panels at time?

A: You can drive many panels by connecting them electrically in series. So you have the same current going through each panel and you get the same luminous output for each panel if they are the same products. Thus you can drive for example 4-panel luminaire with one driver as long as the voltage range of the driver allows you to do so.

Q: Which temperature range is allowed for OLED panels?

A: Basically, OLED lighting can be used only in indoor lighting at the moment. For example, LG Display informs in the datasheets of their panels, that operating temperature has to be over zero degrees of Celsius, and this applies also to storage temperature. Only transport temperature can be lower than zero degrees of Celsius, but only for a limited time.

Typical recommended operating temperature range is 0..40°C.

Q: What kind of new application can be done with OLED?

A: One interesting application is so-called transparent connection. In this case the panel is attached inside a glass plate. The current/power is then provided to the panel through metal mesh transparent conductive film.

OLED Transparent Connection

Transparent Connection

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