Improved Performance of Organic Light-Emitting Diodes Based on Oligomer Thin Films with Graphene

An organic light-emitting diode (OLED) with a single-layer structure based on the conjugated oligomer 9,9,9 ',9 ',9 '',9 ''-hexakis(hexyl)-2,7 ';2 ',7 ''-trifluorene (HOTF) as active layer with graphene has been studied. Silver was employed as the cathode of the device, while indium tin oxide was used as the anode. To investigate the performance of the OLED devices, optical properties such as the absorption and fluorescence spectra of the spin-coated oligomer and graphene were recorded. The current-voltage (I-V) characteristic of the diodes was determined. Incorporation of graphene into the HOTF-based devices resulted in an improvement of the turn-on voltage to 4.3 V, while the devices with pure HOTF oligomer exhibited a turn-on voltage of 6.1 V as well as better electroluminescence than the pure oligomer devices. Finally, the lifetime of the diodes based on the blend were measured under standard atmospheric conditions, revealing a great improvement.