Title:  Organic Thin-film Transistors and Their Application in Light Detection

Committee:

Dr. Bernard Kippelen, ECE, Chair , Advisor

Dr. Gregory Durgin, ECE

Dr. Elsa Reichmanis, ChemE

Dr. Azad Naeemi, ECE

Dr. Azadeh Ansari, ECE

Abstract:

Thin-film transistors (TFTs) are widely used in backplane circuits in consumer electronics. As a type of TFTs, organic thin-film transistors (OTFTs) have some unique properties and attract many interests, since they can be fabricated through cost-effective and solution-based processes at moderate temperatures on a wide range of flexible and deformable substrates. The research develops high-performance OTFTs with improved operational and environmental stabilities by a universal approach, which balances the effects of two mechanisms causing shifts of the threshold voltage with opposite signs in long-term operation. The compensation of these two effects could be realized by engineering the bilayer gate dielectric comprising an amorphous fluoropolymer (CYTOP) layer and an Al2O3- HfO2 nanolaminate grown by atomic layer deposition (ALD) technique. This compensation mechanism leads to devices with remarkable thermal, environmental, and long-term operational stability that is comparable or superior to that of commercial inorganic TFT technologies. These OTFTs with outstanding stability show great potential in a variety of applications, especially in light signal detection. Therefore, a new concept of organic photodetector based on these OTFTs is demonstrated. The novel organic photodetector consists of a dual-gate OTFT and an organic photodiode (OPD) that operates in a photovoltaic mode without power consumption. The advantages of fast photoresponse of OPD and amplification property of OTFT enable a high photoresponsivity as well as short response time for this novel organic photodetector.