This Small Business Innovation Research Phase I project will focus on development of novel optoelectronic nanomaterials with long photocarrier lifetimes, low recombination losses, and enhanced coupling to infrared (IR) radiation. The innovation which will enable this is the employment of quantum dots (QDs) with built-in charge to create specified three-dimensional potential profiles, where the areas of IR absorption (QDs, QD rows, and QD clusters) are separated from the conducting channels by potential barriers. The charging of dots is realized by selective doping of the interdot space. The resulting long photoelectron lifetime will increase the photoconductive gain and responsivity of sensors based on this innovation. This structure will also decrease the generation-recombination noise and improve the sensitivity of photodetectors. Low recombination losses and enhanced coupling to IR radiation will improve the photovoltaic efficiency of quantum dot solar cells. The Phase I research includes nanoscale design, development of growth and processing technologies, and comprehensive analyses of the test structures and prototype devices. By providing the needed fundamental and technological basis, this program will develop advanced nanomaterials with a number of optoelectronic applications. The broader impact/commercial potential of this project will be development of novel optoelectronic nanomaterials, which will lead to potential breakthroughs in IR sensing and photovoltaics. With appropriate modifications, the technology is applicable to practically all QD materials and structures fabricated by any method. Optoelectronic nanomaterials that combine strong coupling to radiation with long and manageable photocarrier lifetime are crucial for the development of next generation IR sensors. Sensitive detectors operating at room temperature will significantly increase the commercial market of IR technologies, which have applications including industrial and environmental monitoring, chemical sensing, medical diagnostics, and detection of explosives. The high scalability of these structures provides a wide opportunity for imaging applications. When integrated into in p-i-n junctions for solar energy harvesting, these structures will provide an additional ~20% improvement in the conversion efficiency (allowing 45-50% total efficiency without concentrators). In the Phase I project, we will demonstrate that harvesting and conversion of IR radiation in this way adds at least an additional 7% to the total conversion efficiency. The potential high efficiency and relatively low cost (as compared with efficient multi-junction cells) make this technology commercially viable for various photovoltaic applications.
