White OLED efficiency re innovation high luminous efficiency 67lm/W

American scientists use three layers of light-emitting layer (3-EML) structure, so that white light-emitting diodes (white organic light-emitting, WOLED) luminous efficiency significantly improved. Compared with the previously published WOLED, the 3-EML WOLED (luminance) in the illumination for the maximum luminous efficiency of 1000 cd/m2 was 64 + 3 lm/W, color coefficient (CRI) of up to 81, while the typical WOLED color coefficient ranged from 75 to 80 between the most.

Princeton University Yiru Sun pointed out that these components in addition to the current one of the highest luminous efficiency, more importantly, there are also very good CRI, so you can get high-quality white light. The CRI value reflects the color fidelity of the object under the illumination of the light source. Sun said that the development of high CRI value of the light source is very important for indoor lighting applications, CRI value greater than 70 can be seen as the sun's high quality white light.

The electroluminescent WOLED usually contains only one or two layers of light emitting layer, and the electron and hole exciton (exciton) is formed in this region. When the emission layer accumulation, often occur in other scientists headache "Three - three triplet state eliminated" (triplet-triplet annihilation), namely two three singlet exciton interactions, one of them will release energy, fell to the ground, resulting in the decrease of the efficiency of optical components.

Sun found that the use of 3-EML structure, the three light emitting layer respectively emit red, blue and green, because the exciton distribution will produce in the light emitting layer, thus reducing the local density of States and the inhibition of three singlet exciton effect can be eliminated. In addition, the best luminous efficiency and color performance can be obtained by choosing the phosphor which can match the three main RGB (host). Another advantage of the 3-EML structure is that it can adjust the color intensity by changing the thickness of the light emitting layer and the doping concentration to produce a high quality white light.

The team then tested the life of the component, which is a major issue for OLED. Sun said that they will be able to study the application of the three layer of the light-emitting layer structure of the material and the main light-emitting material, in order to obtain higher luminous efficiency and longer service life.

Source: photoelectric News Network