This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
This Small Business Technology Transfer Phase I project will investigate transparent metal oxide nanostructures, especially zinc oxide and titanium oxide, suitable for a wide range of applications that require transparent conductors.
If successful this project will create low cost transparent electrodes for applications such as LCD displays, touch screens, and solar cells.
This Small Business Technology Transfer Phase I project demonstrated the commercial feasibility of metal oxide nanostructure films, especially zinc oxide (ZnO) and indium tin oxide (ITO), which are used in a wide range of applications. In particular, they are used as a transparent electrode for today’s optoelectronics devices, including flat panel displays and touch-screen devices such as smart phones, tablet computers and game consoles. Furthermore, with proper design of nanostructures, it is possible to "tune" into controllable and multi-functional properties during the fabrication process. For example, an electrical property (e.g., conductivity) can be varied on different parts of a film, such as conductive interconnect lines vs. semiconducting switching circuits, by simply changing the process parameters on the same material. While these materials are prepared by complex vacuum deposition and photolithographic pattering processes today, there is a tremendous need to develop a cost-effective, roll-to-roll processing. We proposed to develop solution-based processing ("printing") enhanced by laser processing ("laser firing") to meet this target. The advantages of this hybrid approach are; (1) laser sintering, firing and/or annealing improve the morphology, structure and chemistry of printed precursor materials, to fine-tune the property of nanostructures; in other words, desired electrical and optical properties can be "dialed-in" by laser process parameters, (2) patterning is achieved by laser selective sintering and/or direct-write process, avoiding complex, multi-step photolithography processes, (3) local energy deposition of laser allows selective modification of desired material with minimum thermal influence, thus compatible with low temperature substrates, such as polymers. The test results of this project show that the electrical properties (sheet resistance) of zinc oxide and indium tin oxide films produced by the proposed method are comparable to vacuum processed films and superior to conventionally solution-processed films, with high optical clarity and transparency. Therefore, this process allows achieving high-quality films at a fraction of cost compared to traditional fabrication methods based on vacuum deposition and photolithography. Impact of this project is far reaching, since the transparent electronics is used in day-to-day applications such as displays, touch screens, and solar cells. The use of nanomaterial-based inks and the cost-effective manufacturing solutions developed in this project will help significantly to achieve grid parity when applied to the manufacturing of solar cells. It would also enhance the green manufacturing practice. Furthermore, metal oxide materials and their nanostructures have a potential to create new applications as porous nanostructures are useful in many applications beyond electronics, ranging from water treatment and energy storage devices to sensors and fuel cells. In addition, this project enhanced the front-end scientific understanding of nanomaterials growth and interaction with laser beam.
