Researchers have developed novel Pt(II) complexes, PtON-tb-DTB and PtON-tb-TTB, to improve the stability and efficiency of blue phosphorescent emitters for OLED displays. By modulating the bulky t-butyl groups in distinct positions of the Pt(II) complexes, the new materials were designed to reduce excited state interactions, known as the MMLCT effect. Through molecular dynamics and quantum chemistry simulations, the researchers found that PtON-tb-DTB exhibited reduced steric hindrance, a more distorted conformation, and enhanced vibrational properties compared to PtON-TBBI. These modifications led to improved device performance and stability.
UV-visible and PL spectroscopy revealed that the new Pt(II) complexes had shallower HOMO and deeper LUMO energy levels, resulting in better optical properties. Time-resolved photoluminescence measurements showed that the exciton lifetimes of the new materials were longer than that of PtON-TBBI, indicating reduced exciton quenching effects. Additionally, the new complexes exhibited higher photo-physical properties, such as PLQYs and TRPL, compared to the reference material.
When tested in OLED devices, the PtON-tb-DTB complex showed a significant increase in device lifetime compared to PtON-TBBI, demonstrating enhanced stability. The roll-off characteristics and degradation mechanisms of the devices were analyzed, revealing that reduced MMLCT formation and better geometrical properties played a key role in improving device performance. Overall, the study highlights the importance of material design strategies in developing stable and efficient phosphorescent emitters for advanced display technologies.
