What are the differences between new OLED materials that do not use rare metals and existing materials?

 There are two types of existing OLED materials : "fluorescent materials" that emit light for a short time after voltage is applied, and "phosphorescent materials" that emit light for a long time. Professor Chihaya Ando, ​​director of the OPERA Center, said that the luminescent material developed by OPERA can be regarded as the "third type of luminescent material" after the two.

The basic principle of light emission of the three types of materials is the same. They all set a light-emitting layer with a thickness of about 100 nanometers (nanometer is 1 billionth) between the positive and negative electrodes, and apply voltage to the light-emitting layer. In this way, positively charged "holes" will be generated at the positive electrode, and negatively charged "electrons" will be generated at the negative electrode.

After the two attract and combine with each other, the luminescent material will enter an "excited state" with high energy. Over time, the excited luminescent material will gradually release energy and return to its original state. During this period, the luminescent material will release light and heat. The light enters our eyes in the form of images.

Compared with phosphorescent materials, fluorescent materials are cheaper, but have poor luminous efficiency. Only 25% of the electrical energy generated by the applied voltage can be used for luminescence. The remaining 75% is converted into heat energy and released, so the battery will be exhausted quickly.

Phosphorescent materials can use 100% of electrical energy to emit light, and can convert 75% of energy that is discarded as heat energy into light energy. Professor Adachi of OPERA uses "rare metals such as platinum and iridium" as additive materials to achieve this conversion function.

However, these rare metals are expensive, unevenly distributed, and unstable to purchase. Using them in large quantities will inevitably increase costs and risks in stable production. Currently, the cost of phosphorescent materials is extremely high, more than 10 times that of fluorescent materials.

Fluorescent materials and phosphorescent materials each have their own strengths, and neither of them has a decisive trump card. If this continues, it will be difficult for the competitiveness of LCD to surpass that of LCD.

OPERA has developed a material that can achieve high luminous efficiency without using expensive rare metals. By improving the molecular structure, the material can convert 75% of the electrical energy released by fluorescent materials in the form of heat into light energy without using rare metals.

The development process was arduous. Professor Adachi of OPERA said that the principle of the third type of material "has been around for a long time and is written in textbooks. It is not new." However, it is not easy to achieve a molecular structure that can achieve efficient light emission without using rare metals. For this reason, "(Researchers) re-examined the structure of organic matter as a light-emitting material from scratch."