Author: Ashley Johns
Johns, Ashley, 2016 Organic Diodes Toward Radio Frequency Identification, Flinders University, School of Chemical and Physical Sciences
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The diode fabrication parameters were the primary focus of this project and their influence on the electrical properties of the diodes. The testing conditions and method have also been investigated because they have an impact on the electrical properties. Specific electrical properties investigated were series resistance, shunt resistance, rectification ratio and ideality.
The primary driver for this project was to overcome the affordability issues of RFID tags. RFID tags require ICs (integrated circuit) for power rectification and data processing. The ICs are the basis of RFID technology but have reached a limit of minimum cost due to the expensive manufacturing techniques. Printable OSCs (Organic Semiconductor)s are posed as an excellent alternative, in particular soluble conductive polymers lend themselves to a variety of printing techniques. Although transistors receive much of the focus of OSC research, diodes are just as important in RFID devices, particularly rectification circuits. There are many challenges to be overcome before organic electronics can be produced for the commercial market, particularly for RFID. Some challenges include, low mobility, capacitance effects at high frequencies, refinement of fabrication techniques and sheet resistance. All of these areas warrant research effort to realise OSC as diodes in RFID logic and rectification circuits.
The fabrication method of the diodes developed as the project progressed. When a reproducible method was developed, different variables were altered to investigate the effect on the electrical parameters. The parameters were then extracted from the J-V characteristic curves.
Two fabricated diodes were incorporated as the active component in half-wave rectifier circuits. The circuits successfully rectified alternating current into half-wave current. Through appropriate choice of components direct current could have been realised.
The main result was an OSC diode with a rectification of ~7.5 x 105 : 1 which is still a long way from crystalline inorganic Schottky diodes that typically have a rectification ratio in the range of 100,000,000,000:1. An exceptionally significant result was the effect of the drying time, between spin coating a sample and annealing the sample. Diodes with drying time less than 1 minute performed poorly; whereas diodes with drying time greater than 6 minutes performed exceptionally well.
Keywords: P3HT, organic diode, diode, RFID, radio frequency identification, electrical properties, morphology, rectification, series resistance, shunt resistance, rectification ratio, ideality, Schottky, poly(3-hexylthiophene-2,5-diyl),
Subject: Chemistry thesis
Thesis type: Masters
Completed: 2016
School: School of Chemical and Physical Sciences
Supervisor: Professor David Lewis