| 초록 |
We investigated the degradation mechanism of organic light-emitting devices which employed a series of tris-cyclometalated Ir(III) complexes having N-heterocyclocarbenic ligands as blue-phosphorescent dopants. We proposed that generation of a radical ion pair between a host and the dopant would be responsible for short device longevity. The radical generation is due to intermolecular electron transfer between a host exciton and a dopant, as judged from positive driving forces. We directly monitored the formation and decay of radical ion pairs employing photoinduced EPR and transient laser spectroscopy. In particular, the rate constants for charge recombination (kBeT) within the radical ion pair were determined. A linear correlation was found between the kBeT values and the devices lifetimes (LT95), which reveals the importance of suppression of radical ion pairs and acceleration of radical recombination. |
