Technical: This research project investigates growth and properties of dilute nitride GaNP core/shell nanowires and studies their potential for efficient solar cell applications. The dilute nitride GaNxP1-x is unique among the common semiconductors in that it has a large bandgap bowing and its bandgap can cover a wide range of solar spectrum for relatively small concentrations of nitrogen. Photons are absorbed in both the core and the shell of the GaNxP1-x/GaNyP1-y core/shell nanowires, and photogenerated electrons and holes are separated by the type-II staggered band alignment of the core and the shell, relaxing the requirement of long minority carrier lifetime in a planar solar-cell device. The GaNP-based coaxial nanowires can potentially be a viable alternate to the current triple-junction technology because of its less stringent requirement on material quality (due to spontaneous electron hole separation), simpler processing (due to only one junction), and lower materials cost.
The project addresses basic research issues in a topical area of materials science with high technological relevance. The research, if successful, can have significant impacts on solar-cell development using nanoscience and nanotechnology. The research activities promote interdisciplinary training for graduate and undergraduate students in growth and characterization of novel compound semiconductors and in solar cell design, fabrication and testing, as well as written and oral presentations. The PI is the Director of the California State Summer School for Mathematics and Science (COSMOS) residential summer program for more than 100 high school students. The results of this research can be incorporated into the curriculum and extend to the high schools through the Teacher Fellow program of COSMOS.