Investigation of Device Characteristics in Alternating Current-Driven Organic Light-emitting Diodes and Graphene Field Effect Transistors Modified with Self-Assembled Monolayer on Silicon Dioxide Substrates

In the past decades, thin film displays caught all eyes and had risen to the dominating position in display technology, as a potential branch in which flexible displays become the new favorite these days. In the present thin film display structure, organic materials along with graphene transistors are regarded as one of the potential ways to realize this concept. In this work, we investigate the device characteristics of organic light-emitting diodes (OLEDs), especially driven by alternating current (AC), and graphene field effect transistors (GFETs) with evolved transfer technique and modified substrates.
In the first part, we demonstrate an AC-driven OLED with LiF insulating layers using simple thermal evaporation. The device is equipped with relatively lower turn-on voltage and favorable luminance, which is nearly identical to the devices with HfO2 insulating layers reported. Ultraviolet photoemission spectroscopy (UPS) and inverse photoemission spectroscopy (IPES) are employed simultaneously in an ultrahigh vacuum (UHV) chamber to examine the electronic band structure of AC-driven OLED, which enables us to deeply investigate the operating principle of AC-driven OLED. In addition, the electronic band structure obtained fully explains optical properties and electrical characteristics of AC-driven OLEDs.
In the second part, we demonstrate GFETs transferred via polymer-involved and polymer-free techniques on self-assembled monolayer (SAM)-modified substrates. The GFETs on SAM-coated SiO2 substrates all show better performance as compared to those on bare SiO2 substrates. Several verifications on the two transfer techniques are also investigated in parallel. The best GFETs on SAM-coated SiO2 substrate via polymer-free transfer technique exhibits extremely high mobility of 11000 cm2/V∙s at room temperature, which is much higher than the devices in prior researches. Furthermore, the mixed-solvent doped graphene is adopted as channels of p or n-type GFETs as well and the doping effect is considerably effective.