Title:  Organic Field-effect Transistors on Novel Renewable Substrates

Committee: 

Dr. Kippelen, Advisor    

Dr. Brand, Chair

Dr. Mukhopadhyay

Abstract: The objective of the proposed research is to develop high-performance organic field-effect transistors (OFETs) on novel renewable substrates that are environmental friendly. To achieve this goal, the first task in the preliminary research was to fabricate top-gate OFETs with a TIPS-pentacene/PTAA blend as a semiconductor layer and CYTOP/Al2O3 as a bilayer gate dielectric layer on cellulose nanocrystal (CNC)/glycerol substrates, which can be dissolved in water at room temperature. From our group’s experience with spin-coating organic electronics on bare CNC/glycerol, we found that direct fabrication on CNC/glycerol may cause some issues. To alleviate these issues, we deposited a barrier layer of ALD-grown Al2O3 on top of CNC/glycerol to compare OFETs on bare CNC/glycerol with the barrier layer on CNC/glycerol. The mobility of OFETs on CNC/glycerol with the barrier layer was comparable to that of OFETs on plastic substrates, and the stability was much greater than that of OFETs on bare CNC/glycerol. The second task was to reduce the contact resistance of OFETs. The contact resistance of OFETs comes from the work function mismatch between the organic semiconductor layer and source and drain electrodes, which produces a current injecting barrier. To reduce contact resistance, we typically use two approaches: modifying the work function of source and drain electrodes or doping the semiconductor layer. By depositing a layer of Mo(tfd)3 on top of the source and drain electrodes, contact resistance significantly decreases. The proposed work should improve the stability of OFETs by developing a more stable bilayer gate dielectric and barrier layers for OFETs and CNC/glycerol substrates.