Triplet Energy Transfer between a Sacrificial PMPand Blue TPF2 Iridium Dopants Leading to Enhancement of OLED DevicePerformance

In this study, we prepared phenylimidazole-based C^N-cyclometalated Ir(III) complexes (DMP, TPF2) and C^C-cyclometalated Ir(III) complex (PMP), and investigated the energy transfer process by examining the intermolecular interactions between the two cyclometalated Ir(III) complexes. In films doped with 3% Ir(C^C)3 complex (PMP) and 15% Ir(C^N)3 complex (DMP or TPF2), the PMP effectively induced energy transfer to the DMP or TPF2. This intermolecular energy transfer process was investigated using a picosecond time-resolved emission spectroscopic method. In the case of mixing PMP with DMP, where two types of luminescence were observed at 470 nm and 580 nm, the emission at 470 nm was due to DMP, while the emission at 580 nm can be assigned as the intermolecular exciplex emission. By contrast, in the case of mixing PMP with TPF2, the emission at 465 nm corresponding to the PMP emission region decreased for 18.5 ns, while the emission at 530 nm corresponding to TPF2 increased. This emission can be attributed t...