Date of Award
12-2025
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Electrical Engineering
Committee Chair/Advisor
Dr William Rod Harrell
Committee Member
Dr. Judson Douglas Ryckman
Committee Member
Dr. Chad Everett Sosolik
Abstract
In this study we are investigating and comparing the hysteresis observed in I-V characteristics of Poly(3-hexylthiophene -2, 5-diyl) (P3HT) Organic thin film transistors (OTFT) with and without interfacial layers. We are also investigating how electrical characteristics of P3HT OTFTs is affected by irradiation with Ar8+ ions.
Hysteresis is an undesired phenomenon that affects transistor reliability and performance. In this study on OTFTs, P3HT was used as the organic semiconductor, with silicon dioxide (SiO₂) as the Gate dielectric. Two interfacial layers—graphene oxide (GO) and a copolymer, poly(oligo(ethylene glycol) methyl ether methacrylate–glycidyl methacrylate–lauryl methacrylate) (POGL)—were introduced between the semiconductor and dielectric layers in order to investigate their effect on device behavior, and in particular, Hysteresis.
Transistors with GO interfacial layer showed improved charge transport compared to devices without an interfacial layer, in particular enhanced mobility, which is most likely due to a reduction in grain boundary traps; however, there was little impact on hysteresis. In contrast, the transistors with a POGL interfacial layer showed increased hysteresis due to deep trap formation at the semiconductor/dielectric interface.
The P3HT transistors were also irradiated with Ar⁸⁺ ions at energies of 14 keV, 32 keV, and 60 keV. Ion irradiation can disrupt chemical bonds and partially damage the thiophene backbone, leading to loss of conjugation and therefore reduced conductivity. At 60 keV, both transfer and output characteristics exhibited a decrease in drain current, while at the lower energies, the output characteristics often showed an increase in drain current, while the transfer characteristics decreased. It was observed that mobility generally decreased after irradiation while the threshold voltage became less positive. Hysteresis also decreased in all devices after irradiation. These observations are attributed to the combined effects of structural damage and deep trap formation. Overall, this study demonstrates how interfacial engineering and ion irradiation influence charge transport, trap dynamics, and device stability in P3HT transistors.
Recommended Citation
George, Riya, "Analysis of Hysteresis in Poly(3-Hexylthiophene) Based Organic Thin Film Transistors With and Without Interfacial Layers and Effects of Ion Irradiation on Poly(3-Hexylthiophene) Transistors" (2025). All Theses. 4640.
https://open.clemson.edu/all_theses/4640