Comparison of different organic solvents used in the luminescent material for OLED devices

Abstract

In this work, organic light-emitting diode (OLED) devices were mounted using the structure: glass (as substrate)/indium tin oxide (ITO) (as anode)/poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) (as hole transport layer)/poly[9,9-dioctifluorene-alt-bis-tienilene(benzotiadiazole)] (PFTB) (as luminescent material)/aluminum-doped zinc oxide (AZO) (as electron transport layer)/aluminum (as cathode). The PFTB was synthetized at laboratory and diluted in different organic solvents as chloroform and trichlorobenzene. The I-V curves of OLED devices showed that the trichlorobenzene used to dillute the PFTB improved the performance for OLED devices promoting the highest electrical current of ≈50 mA and the lowest range of thresold voltage from ≈2.5 to 5 volts, while the device OLEDs mounted with PFTB dilutted in chloroform presented maximum electrical current of ≈23 mA and range of thresold voltage from ≈5 to 8 volts. A hypothesis that explain these results can be attributed to the boiling point of the organic solvent of trichlorobenzene (≈214.4ºC) to be higher than the one of the chloroform (≈61.1ºC), favoring better rearrangement of the polymer chains of PFTB and interfaces between thin films PFTB/PEDOT:PSS and PFTB/AZO improving the injection of charges (holes and electrons) inside the OLEDs devices.