2:00 PM - 2:15 PM
△ [17p-D102-4] Development of New Amorphous Oxide Semiconductors with Deep Conduction Band Minimum and Their OLED Application
Keywords:Amorphous Oxide Semiconductor, Organic Light-Emitting Diode, Hole Injection Layer
Charge injection/extraction has been a crucial issue to achieve high efficiency in optoelectronics including organic light emitting diodes (OLEDs) and solar cells (OSCs). Transition metal oxides (TMOs) including MoOx have been well used as hole injection layers (HILs) because their conduction band minimum levels (ECBM) consisting of vacant metal d-orbitals have good energy alignments with the HOMO levels of organic materials. However, the low-temperature-fabricated TMOs exhibit poor electrical properties owing to their orbital disordering, thus, only several-nanometers-thick TMO layers are applicable to OLEDs to avoid unwanted series resistance. While, we focused on amorphous oxide semiconductors (AOSs) because they have a variety of advantages such as high transparency, large mobility, good flexibility, and low-temperature process. However, conventional AOSs have relatively shallow ECBM of ~4.5 eV that is not suitable to HIL. Therefore, it would be attractive if the AOS material with deep ECBM is realized.
In this study, we successfully fabricated a new AOS material for HIL, amorphous In-Mo-O (a-IMO), with a large Hall mobility of ~1 cm2/Vs, very deep ECBM of 5.6 eV that is close to the HOMO levels of the conventional organic materials in OLEDs/OSCs. Consequently, the OLED using a very thick a-IMO of ~100 nm as a HIL exhibits no operating voltage shift compared to that using a ~5 nm thick a-IMO. Furthermore, a-IMO exhibits very strong chemical stability against a variety of solvents such as water, toluene and DMSO. These results suggest that a-IMO is a very promising material that can improve the leakage-current issue, production yield and optical optimization in conventional organic optoelectronics.
In this study, we successfully fabricated a new AOS material for HIL, amorphous In-Mo-O (a-IMO), with a large Hall mobility of ~1 cm2/Vs, very deep ECBM of 5.6 eV that is close to the HOMO levels of the conventional organic materials in OLEDs/OSCs. Consequently, the OLED using a very thick a-IMO of ~100 nm as a HIL exhibits no operating voltage shift compared to that using a ~5 nm thick a-IMO. Furthermore, a-IMO exhibits very strong chemical stability against a variety of solvents such as water, toluene and DMSO. These results suggest that a-IMO is a very promising material that can improve the leakage-current issue, production yield and optical optimization in conventional organic optoelectronics.