This project will study nanometer-scale semiconductor particles, or nanocrystals, in which electronically active impurity atoms (or dopants) have been incorporated. Even without such dopants, semiconductor nanocrystals, also known as colloidal quantum dots, can exhibit unique and potentially useful properties due to their small size. The addition of impurities to such particles is of interest for three reasons. First, the critical role that dopants play in semiconductor devices, such as the transistor, provides a strong motivation to study doped semiconductor nanocrystals. Second, impurities in nanocrystals should exhibit even more dramatic behavior than in bulk semiconductors because the dopants are confined in extremely small volumes. Finally, doping can help address key problems in potential applications of nanocrystals (e.g., light-emitting diodes and solar cells). In particular, many such applications are trying to utilize thin films of densely-packed nanocrystals, and electronically active impurities can enhance the conductivity of these films.
After several decades of effort, a few groups have very recently demonstrated the first examples of colloidal nanocrystals with electronically active impurities. In this project, two Ph.D. students and one postdoctoral researcher will investigate these materials. The team will also work with four external collaborators to leverage SNF funding. The main goal of the research will be to understand the fundamental properties of doped nanocrystals. To achieve this, the project team will (i) collect data on their optical, electrical, and structural properties and (ii) generate theoretical models from detailed calculations of dopant energetics. During the project, the team will also continue to develop new doped materials.In addition to training two Ph.D students and a postdoctoral researcher, the expected outcome of the project is an understanding of the fundamental properties of doped nanocrystals and how they can impact nanocrystal devices and applications. Early experiments have already shown interesting and unexpected behavior, and further surprises are expected.