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Doctoral Dissertation Announcement
Candidate: Sooman Lim
Doctor of Philosophy
Department: Paper Engineering, Chemical Engineering, and Imaging
Title: Inkjet Printability of Electronic Materials Important to the Manufacture of Fully Printed OTFTs
Dr. Margaret Joyce, Chair
Dr. Paul D. Fleming III
Dr. Sasha Pekarovicova
Dr. Brad Bazuin
Date: Monday, June 4, 2012 10:00 a.m. to Noon
Parkview Campus, Room B231
In this study, the development and printability of ink-jet-printable materials important to fabricating organic thin film transistors (OTFTs) was researched with inkjet technology. In order to understand the jetting evolution based upon inkjet characteristics, simulations were performed with a nano copper ink and sub nano silver ink. To predict the inkjettability of the nano copper ink, the Z and Oh number for different temperatures was determined. The results from the simulation studies were compared to experimental results obtained using a Dimatix inkjet printer. As for the semiconductor, inkjet printability of two organic semiconductors, P2TDC17FT4(poly[(3,7-diheptadecylthieno[3,2-]thieno[2’,3’:4,5]thieno[2,3-d]thiophene-2,6-diyl)[2,2’-bithiophene]-5,5’-diyl] dissolved in 1,2-dichlorobenzene and P3HT (poly-3 hexylthiophene) were compared to figure out the relation between drop speed, drop volume and firing voltage as well as the influence of drop spacing and substrate temperature on print quality. Through this research, the printability and print quality was sufficient to realize fully inkjet printed, top gate OTFTs. The performance of the P2TDC17FT4, printed under ambient conditions, has important implications to the realization of low cost fully printed OTFTs.
As a post processing study, sintering gnano copper ink, is a promising material to replace Ag ink, with IPL (Intensive Pulsed Light) system was researched. Especially, the relationship between ink film thickness and energy required for sintering by intensive pulse light was focused on. In conclusion, the greater the number of sintered nanoparticles, the higher the conductivity of the printed traces. A comparison of energy levels required for sintering on glass and PET in relationship to ink film thickness is reported and the thermal contribution of the substrate to the processing requirements of this ink revealed. All findings through this research will be used to advance our understanding of the material properties needed and challenges remaining to attain a fully printed OTFT with inkjet technology.