Fabrication and characterization of organic transistors by inkjet printing

Author(s)

Josiani Cristina Stefanelo

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2014-07-02

Examining board members

Roberto Mendonça Faria; Leni Campos Akcelrud; Debora Terezia Balogh; Fernando Josepetti Fonseca; José Alberto Giacometti

• Advisor: Roberto Mendonça Faria

Abstract

The technology of inorganic semiconductors has dominated the industry of electronics for many years. However, since the discovery of conductive polymers considerable effort has been devoted to studies and technological applications of these materials in electronic devices, starting a new branch of electronics: Organic Electronics (OE). One of the great advantages of OE lies in the processing methods. The organic materials are easily handled in solution, thus allows the use of various deposition techniques, as for example the printing techniques. Among the techniques of printing, inkjet is showing to be more suitable for printing circuits. It allows you to deposit solutions (or suspensions) volumes on the order of picoliters in each drop, performing well-defined patterns. Furthermore, it eliminates the use of masks, resulting in reduced costs and material waste. This thesis is dedicated to the field of inkjet technique, specifically for the fabrication of organic field-effect transistors (OFETs), p-type and n-type, and application in a unipolar logic inverter. Printed OFETs used architecture top gate/bottom contact (TG/BC). The semiconductor films were formed by several printed lines on the region of the source and drain electrodes. For p-type OFETs we used poly (3-hexylthiophene ) regio-regular (rr-P3HT) as semiconducting material. The p-type OFETs were fabricated using the four different patterns of deposition of the printer Autodrop. These OFETs showed mobility around 3x10-3 cm2/V.s and Ion/Ioff ratio of the order of 103 for the deposition pattern parallel and perpendicular to source and drain. For the n-type OFETs the semiconductor used was Poly{[N,N\'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5\'-(2,2\'-bithiophene)]} (P(NDI2OD-T2)). Among the printed n-type OFETs the best showed mobility around of 10-2 cm2/V.s and Ion/Ioff ratio of the order of 5x102. Both printed OFETs were applied in unipolar digital logic inverters, with gains greater than 1. (AU)

• FAPESP's process: 09/11304-5 - STUDY OF CMOS CIRCUITS BUILD BY INKJET PROCESS
• Grantee: Josiani Cristina Stefanelo
• Support Opportunities: Scholarships in Brazil - Doctorate