Researchers develop a unified framework to diagnose what really limits blue PHOLED lifetime

Researchers from Kyung Hee University published a new study in Advanced Functional Materials that studies the the causses of the short operational lifetime of blue phosphorescent OLEDs. 

The researchers say that intrinsic material toughness (things like bond dissociation energy and molecular rigidity) is not enough to predict how long a device will actually last, because materials with very similar chemical stability can show dramatically different lifetimes. To get to the root cause, the researchers combined two complementary characterization techniques: transient photoluminescence (TrPL), which measures a material's intrinsic exciton behavior under optical excitation, and magneto-electroluminescence (MEL), which probes exciton dynamics under actual electrical operation.

They built exciplex-based test devices using a single p-type host (SiCzCz) paired with four structurally similar n-type hosts (SiTrzCz2, DSiCzTrz, SiCzTrz and mSiTrz). Despite their chemical similarity, the four devices showed widely different LT50 lifetimes, ranging from 272 hours down to just 55 hours. This gave the team a way to isolate exciton dynamics from material chemistry.