SBIR-STTR Award

This Small Business Innovation Research Phase I project will establish the feasibility of constructing a semiconductor device that directly and efficiently converts the energy released from radioactive decay directly into electric current. The semiconductor material will be utilized in a unique manner that will result in an innovative electrical technology. Prior efforts using semiconductor materials to accomplish direct radioisotope energy conversion have concentrated on planar geometries as in, for example, solar and photovoltaic cells. The goal of this research is to distribute the radioisotope throughout the specified active volume of a semiconductor in such a manner as to remain nearly proximate to the energy conversion mechanism. The key to achieving high efficiency is to situate the maximum number of radioactive nuclei so that a minimal amount of decay energy is lost before conversion to electric current occurs. Commercially, this research will lead to the development of a practical nuclear battery. It is anticipated that this direct energy conversion device would be able to replace chemical batteries in a number of applications. Especially attractive is that candidate radioisotope power sources have half-lives measured in decades so that electric current can be delivered continuously in remote or inaccessible locations. Potentially, acceptance and success in the industrial marketplace will lead to a number of consumer applications

This Small Business Innovation Research (SBIR) Phase II project will fabricate a prototype betavoltaic battery in a form factor the size of a quarter coin. The goal will be to generate approximately 100 microwatts of electrical power in a volume less than half a cubic centimeter from a tritiated energy source. Research conducted for the Phase I portion of this project established the feasibility of constructing a semiconductor device that directly and efficiently converts the energy released from radioactive decay directly into electric current. Three dimensional (3D) diodes were constructed in macroporous silicon by placing p-n junctions along the walls of all the pores. These junctions formed the betavoltaic conversion layer for beta particles (electrons) emitted by gaseous tritium (the radioisotope of hydrogen with a half life of 12.3 years) that was distributed throughout the pore space. Measurements of the current-voltage responses for this novel 3D geometry demonstrated an order of magnitude efficiency increase compared to conventional 2Dplanar diodes. In the 3D diode nearly every decay electron entered the p-n conversion layers. The focus of the Phase II research will be to enhance the performance of the 3D diodes to maximize conversion efficiency. Also, the source energy density will be increased markedly by developing a tritiated solid that can be easily and routinely dispersed in the pore space. This research will lead to the development of a practical nuclear battery. Commercially, betavoltaic batteries will be useful in a wide variety of sensors and devices used for remote and extended missions in many inaccessible locations. Successful commercialization of this nuclear battery with its order of magnitude increase in useful life is to increase significantly the utilization of self-powered devices and sensors. Stringent efforts will be made to ensure the radiological safety of these nuclear batteries at every step in the development, manufacturing and commercialization processes