SBIR Phase II: Self Assembled Nanocrystal Thin Film Transistor

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This NSF Phase II SBIR program aims to develop and demonstrate large area and high performance nanocrystal thin film transistor (NC-TFT) based active matrix backplanes for flexible display applications. A novel electrostatic self assembly (ESA) technology will allow significant cost reduction using organic, inorganic and hybrid materials. Such a molecular-level self-assembly approach to form TFT materials and devices offers numerous advantages since very different materials can be incorporated uniformly, using the same chemical process at room temperature, thus allowing the formation of TFT films on virtually any substrate material. During Phase I, single and arrayed NC-TFT devices were developed on rigid and flexible substrates with reliability and performance comparable to that of amorphous silicon based TFT devices. High-K hybrid gate dielectrics, such as ZrO2/SiO2 hybrid thin films, were also deposited through the same ESA method. These films exhibited a dielectric constant larger than that of SiO2 (4.7 versus 3.9). Self-assembled gold nanoparticle-based memory devices. I-V tests were also investigated and fabricated. I-V tests were conducted on the self-assembled TFT devices, as well as on operational memory devices. The field effect mobility of the prototype TFTs can reach 0.3 cm2/V/s and an On-Off ratio of 1000 was achieved. We also fabricated TFT-based gas sensors, which demonstrated high sensitivity to certain gas species such as ammonia. In the current project, we will design and develop prototype NCTFT-based active matrix backplanes on flexible substrates with improved efficiency and performance and reduced cost, and beta-test those backplanes integrated with the E-paper based flexible display films and partners' flexible electronics and sensor platforms. This project also aims to establish a complete manufacturing process that is ready for production and licensing to selected flexible display customers. The broader impact/commercial potential will be the development of flexible displays that offer many potential benefits over other display technologies, including reductions in cost, weight and power consumption, improved performance, ruggedness, and reliability. Other near term applications include 1) direct replacement for conventional circuit boards, wiring harnesses and flex interconnects on army vehicles, 2) as integrated sensing, signal processing and communicating clothing for army personnel, 3) electronic applications such as RF ID tags, antennas and stealth coatings, and 4) very large, mechanically-flexible deployable systems. This research has shown promise in producing devices of acceptable efficiencies at significantly reduced cost using organic, inorganic and conductive polymer materials. A revolutionary breakthrough in reducing the costs of TFT devices may be achieved if the semiconductor is deposited from solution onto large flexible substrates in roll-to-roll coating machines.