ABSTRACT
Vertical channel Organic Thin Film Transistors (VOTFTs) operating current, quinoline aluminium (Alq3) layer will emit light when the current flowing through (Ahmad et al. 2010).
2 EXPERIMENT
The structure of VOTFTs is shown in Figure 1. Selecting model parameters for the conduction channel width 2a = 400 nm, a gate thickness LG = 300 nm, the distance between the gate electrode and the source electrode or between the gate electrode and the drain electrode is LGS = LDG = 200 nm. The organic layer CuPc is a transporting material for hole, which the HOMO level is −5.1 eV and the LUMO level is −3.5 eV, and it is widely applied in organic thin film transistors. Alq3 is a light-emitting layer and the luminous intensity depends on the number of carriers. For
1 INTRODUCTION
Organic electroluminescent devices have attracted much attention for their diversity of device fabrication processes, low material cost, ability to be used for multi-coloured or full-colour displays and suitability for large areas in the field of optoelectronic devices and flat panel displays (Min et al.2014, Feldmeier and Melzer 2011, Aleshin 2014, Melzer and Heinz 2010). However, due to the low conductivity of the organic semiconductor and small carrier mobility, leading to its operating characteristics such as low switching speed and high drive voltage (30-100V), it is difficult to practical application. An image charge is produced on the semiconducting layer of the Al film side, so the effective Schottky barrier height of copper phthalocyanine (CuPc)/ Al interface in the drain region decreased. Carriers emitted by the source which tunnel through the Schottky barrier in the gate region and form the
the CuPc/Al/CuPc structure, both sides of the gate electrode comb Al with CuPc have a good contact, and a Schottky barrier is formed, so the characteristics of transistors will be achieved when the gate-source or the drain-source voltage is applied, the device transistors characteristics fail if there is a problem with either side of the contact. Using a practical comb Al with an Atomic Force Microscope (AFM) observations were obtained; they are shown in Figure 2. We can know that there are continuous and discontinuous crystalline clusters along the Al electrode edge, the actual production of the Al electrode width is larger than the design
value. In the case of considering only continuous Al crystals, each electrode gap is 5μm. While discontinuous Al crystallisation point forming isolated dot gate. These isolated dot gate contacts with the CuPc film form a Schottky barrier and depletion layer so that the effective conduction channel area is decreased, the effectiveness of the electrode gap is significantly smaller than the AFM observation image of 5μm.
