有機EL材料の新しい発光メカニズムを解明New light-emitting mechanism of organic electroluminescent materials elucidated

This research focused on the energy relationship between two types of excited states, “singlet” and “triplet.” Normally, singlet states have higher energy, but in recent years, materials have been reported that exhibit a unique phenomenon known as “InvEST (inverted singlet-triplet),” in which this relationship is reversed. This phenomenon has attracted attention due to its potential to lead to ultra-efficient luminescence. However, in materials where the energy difference is extremely small or even negative, it has been difficult to accurately evaluate the luminescence mechanism using conventional theoretical models. The research team therefore precisely measured the luminescence spectra and luminescence lifetimes of candidate InvEST materials while varying the temperature and solvent environment. Furthermore, they used an analytical method known as the “dynamic exciton model” to comprehensively analyze exciton spin conversion and energy transfer. The results revealed that the luminescence behavior of the target materials can be explained by the inversion of energy levels.

This result makes it possible to analyze the near-zero energy difference region, which was difficult to evaluate using conventional methods, and is expected to lead to design guidelines for next-generation, highly efficient, low-power-consumption organic electroluminescent materials.