利用原子層沉積技術製備高分子發光二極體之電子注入及阻氣層

Abstract

This study addresses in stability issue of flexible polymer light-emitting diode (PLED) devices with a two-pronged approach based on atomic layer deposition (ALD): developing an inverted PLED device structure—which offers far superior inherent stability to that of the conventional structure—with a dual-functioning electron-injection layer/gas barrier by ALD at plastic-substrate-compatible temperatures, and developing a thin-film encapsulation technique by ALD that is compatible with the inverted PLED device. ALD ZnO was used as the electron-injection layer (EIL)/gas barrier, and a range of plastic-compatible deposition temperatures (70-90℃) were examined. Lower deposition temperatures were found to yield superior device performance, because they yielded lower carrier concentrations which allowed more effective hole-blocking at the cathode of the PLED devices, and they provided better gas-barrier function as a result of their low crystallinity. When applying an ALD HfO2/Al2O3 nanolaminated film to the PLED devices as an encapsulation layer, we observed severe encapsulation-induced degradation due to aggregation of our MoO3 hole-injection layer at the ALD temperature of 90ºC. We eliminated this degradation by developing a low-temperature (70 ºC) ALD process of Al2O3/ZnO nanolaminates, which combined with the ZnO EIL/gas barrier enabled plastic-based PLED devices to retain ~90% of their initial luminance upon storing in air for 1610 hours.