Cyclometalated iridium complexes, e.g., Ir(2-phenylpyridyl)<sub>3</sub>, are widely used as phosphorescent dopants in organic light emitting diodes (OLEDs) due to their highly efficient luminescence.  The photoluminescence efficiency (PLE) from these complexes can approach 100%, yet many derivatives, particularly blue emitters, have values that are significantly lower (PLE &lt; 1%) at room temperature.  The PLE is mainly dependent on the type of process that contributes to the nonradiative decay. Phosphorescence from these compounds typically originates from a mixed ligand-centered/metal-to-ligand charge transfer excited state.  Nonradiative deactivation of the excited state occurs through several distinct mechanisms; self-quenching, direct vibrational decay to the ground state, or thermal population to ligand field states.  The third mechanism becomes dominant for complexes with high (blue) triplet energies and can lead to decomposition of the complex due to loss of ligand(s).   We show that the last mechanism can used to study the formation of degradation products in OLEDs through appropriate design of the device architecture.  This method is employed to serve as an in situ assay for the stability of phosphorescent dopants for use in OLEDs.

Exploiting nonradiative decay of cyclometalated iridium complexes to perform in situ analysis of degradation products in OLEDs<br />

249th National Meeting (2015)

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