A new door for molecular-based organic light-emitting diodes

Long life-time molecular-based organic electronics, such as organic light-emitting diodes (OLEDs), organic solar cells, or organic transistors etc, inevitably demand their constituent molecules to be highly thermal-stable. Coupling with special needs in molecular design, the resultant increasing molecular weight (MW) will eventually make the molecules difficult to deposit if via dry-process, while using wet-process would frequently result in undesired relatively poorer efficiency. Surprisingly, two high-molecule composing OLEDs with relatively high-efficiency were obtained by using solution-process. A blue OLED with a blue dye doped in a novel high-MW, wide band-gap host, 3,5-di(9H-carbazol-9-yl) tetraphenylsilane (SimCP2), yielded 24 lm/W (38 cd/A) at 100 nits, and a green OLED using a novel high-MW green dye, bis[5-methyl-7-trifluoromethyl-5H-benzo (c)(1,5) naphthyridin-6-one] iridium (picolinate) (CF3BNO), yielded 70 lm/W (89 cd/A), while their dry-processed blue and green counterparts yield 1.7 and 21 lm/W, respectively. Importantly, although the comparatively high MW has made the resulting molecules extremely difficult to vacuum-evaporate and has resulted in poor device performance, the wet-process has been proven effective in fabricating two high molecule-containing OLEDs with relatively high efficiency. The successful demonstration suggests that the same approach may as well be extended to other organic devices that compose or should compose high molecules.