Deuterium Effect of Dinuclear Pt(II) Complex in Prolonging Operational Lifetime of OLEDs

Abstract

The butterfly-shaped dinuclear platinum complex, Pt-dinu-D 20 , is composed of nonfluorinated NHC ligands with N-deuterated methyl groups in the imidazole ring, as well as a deuterated ancillary ligand. Pt-dinu-D20 , with a further deuterated ancillary ligand, can increase the device lifetime by about 2.5 times compared with Pt-dinu-D 6 while maintaining an EQEmax of approximately 20%. DFT calculations demonstrate that a high deuterium ratio may play a beneficial role in effectively suppressing the formation of the 3MC state. To elucidate the crucial role of deuterium in prolonging the operational lifetime of OLEDs using dinuclear Pt(II), the stability is studied from both the device and material perspectives through exciton dynamics and HPLC measurements. An increased number of deuterium atoms suppresses the hole trapping of the dinuclear Pt dopant within the EML, thereby mitigating the hole-induced quenching process. This improvement results from the lowering of the HOMO energy level due to deuterium, which facilitates hole injection and minimizes trapping. Additionally, the increasing presence of C-D bonds improves the intrinsic stability of the material by reducing the hole-induced dissociation.