Tandem OLEDs: The Science Behind Them

Tandem OLED is the new development in screen technology

A tandem OLED (organic light emitting diode), also known as a stacked OLED, is a type of screen technology that makes displays brighter and last longer.

Traditionally, OLED screens have only one layer that emits light. In a tandem OLED, multiple light-emitting layers are stacked on top of each other. Each layer emits light independently, increasing the brightness and efficiency of the display.

Screens using tandem OLED technology can be brighter, last longer, and use less power than single-OLED screens. This advanced technology will likely improve many devices, from smartwatches to big-screen TVs.

How Does A Tandem OLED Work?

Tandem OLED screens combine two separate OLED devices, also known as OLED modules. Each module emits light individually and, in some cases, can be independently controlled.

Tandem OLED device is two stacked OLED devices connected to external circuit — Tandem OLED device: Two stacked OLED modules connected in parallel (left) and series (right)

By combining two OLED modules, tandem OLED screens achieve improved brightness and efficiency. In fact, theory says that if you have N amount of OLED modules in a tandem OLED, the efficiency of the tandem OLED device will be N times the efficiency of the single layer device. For example, having three layers would make the device three times more efficient than a device with one layer.

Additionally, the tandem design reduces the wear and tear on each layer by spreading the electrical load across all layers. This increases the lifetime of tandem OLED screens.

How Do OLEDs Work?

OLEDs use organic compounds to produce light when electricity passes through them, through electroluminescence. In an OLED screen, each pixel emits its own light, unlike traditional LCD and LED screens which use a backlight. This allows OLEDs to display true blacks by turning off individual pixels, resulting in high contrast and vibrant colors.

OLED screens are known for their brilliant colors, deep blacks, and thin design. They have been used in many devices, from smartphones and TVs to wearables and more.

Tandem OLED Structure

Tandem OLEDs have a similar structure to traditional OLEDs. Two individual OLED modules, each consisting of an organic emissive layer between two charge transport layers, are stacked. The layer that connects the two OLED modules is the charge generating layer (CGL).

There are several different types of tandem OLEDs, depending on their device structure and emissive layers. For example, OLED modules in a tandem OLED can be connected in series or in parallel:

In series increases the brightness and efficiency
In parallel allows each module to be controlled separately

Benefits of Tandem OLEDs

There are many ways in which tandem OLED technology can improve current display screens.

Brighter and more efficient	Tandem OLED screens are much brighter than single junction OLEDs. They can produce more light as they have multiple light-emitting layers.
Long lasting screens	OLED screens can sometimes suffer from burn-in and wear out quickly. Tandem OLED screens solve this problem by reducing the stress on each layer. This makes the screens last much longer, keeping their high-quality picture.
Lower power consumption	Tandem OLED devices use less power. Spreading the electrical load across multiple layers means a display screen can be just as bright, while using less energy. This helps run display screens more efficiently.
Colour tuning	For OLEDs connected in parallel, you can individually control the ratios of colour of emitted light by sending different amounts of voltage to different layers. This allows you to tune the colour emitted from a single OLED module.
Reduced risk of burn-in	Tandem OLEDs allow you to have a higher level of control. You can control the brightness of each pixel in two OLED modules. This means you can adjust the brightness in each pixel to counteract the effects of burn-in.
Greener technology	Tandem OLED technology is more efficient and lasts longer, meaning they need to be replaced less often and they use less energy. This helps reduce the environmental impact of our electronic devices.

Tandem OLED Applications

Tandem OLED technology can be used in a wide range of applications.

Tablets and Laptops

Leading experts of display screen technology are adopting tandem OLED technology into their device screens. For example, the Apple iPad Pro (M4) Ultra Retina XDR display features tandem OLED technology. LG Laptops also use tandem OLED displays stating that their tandem OLED screens have double the lifetime and triple the efficiency of single-OLED technology, with 40% less power consumption.

Televisions

LG’s new range of OLED TVs, like the LG G3, is also exploring tandem OLED technology. .

Wearables

Wearable tech is another area where tandem OLED is making a big impact. The Apple Watch Series 9 features a Tandem OLED display, ensuring clear visibility even in bright sunlight and extended battery performance for daily use.

Automotive Displays

In the automotive industry, brands like Audi are integrating Tandem OLED displays into their latest models. These displays provide bright and reliable navigation screens and instrument panels that are essential for safe driving.

Future of Tandem OLEDs

By enhancing brightness, extending screen lifespan, and reducing power consumption, tandem OLEDs are set to create high-quality displays in various devices. From consumer electronics to automotive applications, the advantages of tandem OLEDs are vast and exciting.

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Transparent OLED

Transparent OLEDs (TOLEDs) are exciting next-generation electronic devices. The self-lighting pixels form transparent screens that display interactive information. The development of TOLEDs often involves specialized equipment like glove boxes and spin coaters to ensure precise manufacturing. TOLEDs can act as both a window or a panel and an informational or entertainment screen.