Organic Electro-Luminescence

In-house development including OLED material design and fabrication, and panel prototyping.
Aiming for pioneering high-performance OLED displays

Now, OLED displays are the mainstream of displays as well as LCDs, and have been actively developed to pursue higher performance: high efficiency, long lifetime, high resolution, and wide color gamut. To realize high-performance OLED displays, we conduct all the processes in-house including OLED material design and fabrication, and panel prototyping.

First, molecules are designed and their physical properties are predicted through AI and material analysis simulations using a supercomputer; organic synthesis is performed; light-emitting devices are fabricated for testing; then, their characteristics are evaluated. In all the steps, we pursue the optimal materials and devices for displays, leading to fabrication of high-performance OLED display prototypes.

▲Photoluminescence demonstrated in solution

Organic EL materials development
Higher-Brightness and Longer-Life Technology

SEL’s original technology, ExTET®

ExTET, which was originally developed by SEL, is the technology enabling higher efficiency, lower driving voltage, and a longer lifetime of OLED displays. In a phosphorescent OLED, the excitation energy of a host material is transferred to a phosphorescent material (guest material) in a light-emitting layer, so that the phosphorescent material emits light. Conventionally, this energy transfer would cause energy loss to adversely affect the emission efficiency, driving voltage, and lifetime. SEL developed an energy transfer mechanism in which an exciplex (*3) formed by combination of an electron-transport material and a hole-transport material is used as a medium for energy transfer to a phosphorescent material, and applied for a patent for this mechanism in 2011. We named this technology Exciplex-Triplet Energy Transfer (ExTET). ExTET successfully cut the energy loss and thereby solved the problems of the emission efficiency, driving voltage, and lifetime of phosphorescent OLEDs at a time. Being essential for OLED displays, ExTET is a fundamental technology used in the green- and yellow-light-emitting layers of commercially available OLED displays, and sometimes also used in red-light-emitting layers.

Conceptual diagram

Basic mechanism of ExTET

Typical absorption and PL spectra of materials

TTA increases emission efficiency of fluorescent device

In a current-excitation device, there is a 25 % probability (internal quantum efficiency) of producing a singlet exciton leading to fluorescence and 75 % probability of producing a triplet exciton. Thus the emission efficiency of a fluorescent device is lower than that of a phosphorescent device but if an increase in the probability of producing a singlet exciton by some method would increase the emission efficiency. One method is TTA, which is a phenomenon where a singlet exciton is formed in a light-emitting layer by mutual interaction of triplet excitons. We have found a device structure to enhance the probability of producing TTA and developed a fluorescent device with high emission efficiency.

Energy diagram of TTA

OLED fabrication

We have been developing OLEDs as well as materials in our laboratory to pursue optimal device structures for realizing high-performance OLED displays.

▲OLED (Left: red, Right: green)

OLED display development

Jump to OLED Display page

Turning on the light when the room is dark.
Such simple daily actions give us hints for invention.

Organic EL Lighting Panel

The mainstream in lighting is transitioning from incandescent and fluorescent lights to LEDs and organic EL lighting, which provide low power consumption and longer life. In this transition, our focus is on organic EL lighting and we envision a future with more comfortable lighting. Organic EL lighting has low power consumption and long life, and also has excellent color rendering properties which produce light that is close to natural light. It is also favorable environmentally and in design ability, as it is mercury-free, has a surface light source, and is thin, light, and flexible.

We are developing light boards and flexible lighting with the goal of practical application, and we are also striving to improve power efficiency, lifetime, and color rendering properties of organic EL lighting, with the goal of popularizing organic EL lighting.

* ExTET is a registered trademark of Semiconductor Energy Laboratory Co., Ltd. (Japanese trademark registration No. 5666910).