Enhanced lifetime of organic light-emitting diodes using soluble tetraalkyl-substituted copper phthalocyanines as anode buffer layers

This study describes two soluble tetraalkyl-substituted copper phthalocyanines (CuPcs) as hole-blocking materials that can be used in the Alq₃-based organic light-emitting diodes (OLEDs). The hole-blocking characteristics of these Pc layers significantly impeded hole injection into the Alq₃ emitting layer and thus decreased the production of unstable cationic Alq₃ species, giving an enhanced OLED efficiency and stability compared with that of devices containing the widely used PEDOT:PSS. Moreover, the insolubility of the CuPcs in water together with their extremely high thermal and chemical stabilities led to the effective protection of the ITO anode, resulting in the increased operational stability of the OLEDs in air and the enhancement of the OLED durability.