Tanaka Masaki, Chan Chin-Yiu, Nakanotani Hajime, Adachi Chihaya
Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, 184-8588, Japan.
Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan.
Nat Commun. 2024 Jul 16;15(1):5950. doi: 10.1038/s41467-024-50326-9.
The orientation of a permanent dipole moment during vacuum deposition results in the occurrence of spontaneous orientation polarization (SOP). Previous studies reported that the presence of SOP in organic light-emitting diodes (OLEDs) lowers electroluminescence efficiency because electrically generated excitons are seriously quenched by SOP-induced accumulated charges. Thus, the SOP in a host:guest-based emission layer (EML) should be finely controlled. In this study, we demonstrate the positive effect of dipole-dipole interactions between polar host and polar emitter molecules on the OLED performance. We found that a small-sized polar host molecule that possesses both high molecular diffusivities and moderate permanent dipole moment, well cancels out the polarization formed by the SOP of the emitter molecules in the EML without a disturbance of the emitter molecules' intrinsic orientation, leading to high-performance of OLEDs. Our molecular design strategy will allow emitter molecules to pull out the full potential of the EMLs in OLEDs.
在真空沉积过程中，永久偶极矩的取向会导致自发取向极化（SOP）的出现。先前的研究报道，有机发光二极管（OLED）中SOP的存在会降低电致发光效率，因为电产生的激子会被SOP诱导的累积电荷严重淬灭。因此，基于主体-客体的发射层（EML）中的SOP应得到精细控制。在本研究中，我们证明了极性主体分子和极性发射体分子之间的偶极-偶极相互作用对OLED性能的积极影响。我们发现，一种具有高分子扩散率和适度永久偶极矩的小尺寸极性主体分子，能够很好地抵消EML中发射体分子SOP形成的极化，而不会干扰发射体分子的固有取向，从而实现OLED的高性能。我们的分子设计策略将使发射体分子充分发挥OLED中EML的潜力。
