SBIR/STTR Phase II: A Semiconductor Device for Direct and Efficient Conversion of Radioisotope Energy

这个小型企业创新研究(SBIR)第二阶段项目将制造一种外形尺寸为25美分硬币大小的Betavavoltaic电池原型。目标是从氚能源中产生体积小于0.5立方厘米的大约100微瓦的电力。对该项目第一阶段进行的研究确定了建造一种半导体设备的可行性，该设备可以直接有效地将放射性衰变释放的能量直接转化为电流。通过沿所有孔壁放置p-n结，在大孔硅中构建了三维(3D)二极管。这些连接形成了分布在整个孔隙空间的气态氚(氢的放射性同位素，半衰期为12.3年)发射的β粒子(电子)的Betavoltaic转换层。对这种新的3D几何结构的电流-电压响应的测量表明，与传统的2D平面二极管相比，效率提高了一个数量级。在3D二极管中，几乎每个衰变电子都进入p-n转换层。第二阶段研究的重点将是提高3D二极管的性能，以最大限度地提高转换效率。此外，通过开发一种易于和常规地分散在孔隙空间中的氚固体，源能量密度将显著增加。这项研究将有助于开发实用的核电池。在商业上，Betavoltaic电池将用于许多人迹罕至的偏远和延长任务的各种传感器和设备中。这种核电池的成功商业化使其使用寿命增加了一个数量级，这将大大提高自给装置和传感器的利用率。将作出严格努力，确保这些核电池在开发、制造和商业化过程中的每一步都具有辐射安全性。

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.