WHAT DID THE 2010 EARLY CAREER AWARD ALLOW YOU TO DO?
Nanoscale electronic materials have many unique and useful properties but commonly suffer from poor stability. Their high surface area and energy predispose them to oxidation and unpredictable size changes when exposed to air, light, or heat. In particular, many types of semiconductor quantum dots (nanometer-sized crystals with size-dependent properties) are unstable under normal conditions.
To enable application of these materials in next-generation electronic devices like solar cells and displays, it is important for scientists to understand the basic mechanisms of degradation and develop simple yet effective countermeasures.
This Early Career Award enabled us to study how quantum dot films degrade with exposure to air and heat and to develop an extremely effective method to prevent this degradation. This method involves coating a quantum dot film in a solid matrix deposited by atomic layer deposition (ALD), a sequential deposition of chemicals on substrate surfaces that produces very high-quality thin films of materials. The ALD-infilled films are indefinitely stable in air because the coating stops air from touching the quantum dots while also preventing atomic diffusion within the film.
We further demonstrated that the ALD infilling can be used to greatly improve the electronic properties of quantum dot films by removing surface defects and lowering barriers that slow electron motion.
Support from this award allowed us to refine the ALD-infilling method to produce lead selenide quantum dot films that feature both record levels of performance and record stability. This work is paving the way to practical applications for nanoscale electronic materials.
Matt Law is an associate professor in the Department of Chemistry at the University of California, Irvine.
SUPPORTING THE DOE SC MISSION:
The Early Career Research Program provides financial support that is foundational to early career investigators, enabling them to define and direct independent research in areas important to DOE missions. The development of outstanding scientists and research leaders is of paramount importance to the Department of Energy Office of Science. By investing in the next generation of researchers, the Office of Science champions lifelong careers in discovery science.
For more information, please go to the Early Career Research Program.
THE 2010 PROJECT ABSTRACT:
Evaluating the Oxidative, Photothermal and Electrical Stability of Colloidal Nanocrystal Solids
This goal of this project is to bring a fundamental understanding to the degradation mechanisms of semiconducting nanocrystals (NCs) and to introduce new physical and chemical strategies in an effort to improve their operating lifetimes and overall performance in technological applications. The research will use field‐effect transistors and solar cells as model systems to establish the degradation mechanisms and develop effective countermeasures.
By revealing both how NCs degrade in response to environmental stresses (oxidative, photothermal, and electric) and identifying ways to prevent this degradation, the project will greatly improve our ability to develop new materials for applications from a broad range of nanoscale building blocks, including nanocrystals, nanowires and organic‐inorganic hybrid structures.
Y. Liu, M. Gibbs, C.L. Perkins, M.H. Zarghami, J. Bustamante, Jr., and M. Law, “Robust, functional nanocrystal solids by infilling with atomic layer deposition.” Nano Letters 11, 5349 (2011). [DOI: 10.1021/nl2028848]
Y. Liu, J. Tolentino, M. Gibbs, R. Ihly, C.L. Perkins, Y. Liu, N. Crawford, J.C. Hemminger, and M. Law, “PbSe quantum dot field-effect transistors with air-stable electron mobilities above 7 cm2 V-1 s-1.” Nano Letters 13, 1578 (2013). [DOI: 10.1021/nl304753n]
R. Ihly, J. Tolentino, Y. Liu, M. Gibbs, and M. Law, “The photothermal stability of PbS quantum dot solids.” ACS Nano 5, 8175 (2011). [DOI: 10.1021/nn2033117]
Additional profiles of the 2010 Early Career Award winners can be found at: https://www.energy.gov/science/listings/early-career-program.
The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit www.energy.gov/science.