Long-Term Stability of Betavoltaic Battery Model and Prototype Based on Tritium/C-Silicon PN Junction Devices

Long-term stability of tritium voltaic battery was studied by titanium tritide sources in situ radiation and accelerating radiation from low-energy electron beams. The tritium voltaic experimental models and laboratory array battery prototype were made up of titanium tritide sources and c-silicon P+NN+ devices with boronsilicate glass/Si3N4 passivation. The tritium voltaic outputs at different radiation time were compared. The intrinsic dark I-V characteristics of the c-silicon P+NN+ devices and the defects in their surface material were analyzed. The tritium voltaic experimental models under titanium tritide sources in situ radiation kept output stability in 115 days and the intrinsic dark I-V characteristics of c-silicon P+NN+ devices in the models changed little after radiation. Accelerating radiation from low-energy electron beams gave much severe damage in voltaic output of tritium voltaic experimental models than in that in situ radiation of titanium tritide sources under the same radiation fluxncies. But the radiation damage in accelerating radiation took place in the very early radiation term, and then kept stable. The intrinsic dark I-V characteristics of c-silicon P+NN+ devices showed little change and the ESR defects in the device material were not noticeably increased after 60 min of accelerating radiation. Voltaic output and structure integrity of the laboratory array battery prototype were tested during 64 months. The fundamental voltaic unit showed a little larger decrease of 11.4% in voltaic Isc than tritium decay at 64 months. In addition, the electrical interconnection structure of the prototype exhibited partial failure, which should be put much more attention in the future