Samsung Advanced Institute of Technology (SAIT) announced on March 25 that it has carried out a joint study with a research team led by Yoo Young-min of the Department of Advanced Materials Engineering at Ewha Womans University and has become the first that proved the mechanism of deterioration that degrades the lifetime of the OLED blue phosphorescent material and proposed a material design method that can improve it.
OLEDs are self-luminous organic compounds that have a bright screen, excellent contrast ratio and low power consumption. However, unlike the red and green fluorescent phosphorescent materials that have already been commercialized, fluorescent phosphorescent materials are not commercially available because of their short life span, so they are not suitable for long-term use for many years. Only one of four electron-hole pairs (singletons) formed when the energy level of an organic compound is elevated is converted into light, and the conversion efficiency is only 25%. In addition to being converted into three kinds of light (triplet) which cannot be converted by fluorescence, the conversion to triplet up to singlet is converted into light, and the conversion efficiency is 100%.
While analyzing the decomposition pathway of blue phosphorescence, the researchers have identified a mechanism that accelerates the deterioration of charge separation species formed during the electron transfer process between phosphorescent elements. The charge separation species are a state in which a molecule with no electrical polarity changes its properties as it acquires or loses electrons from its surrounding molecules.
The researchers also found that the lifetime difference up to several tens of times was caused by the rate of charge separation, and suggested a material combination structure that could extend the lifetime by eliminating charge separation species as soon as possible. If this technology is commercialized, it will be possible to dramatically increase the lifetime and performance of OLEDs that use fluorescent materials, not blue phosphorescent materials, among the three primary colors of red, green, and blue.
The findings are published online in the journal Nature Communications. The future goal of the researchers is to find a blue phosphorescent material that can minimize deterioration through further research and apply it to real systems.