Temperature Dependence of Commercially Available Betavoltaic Cells

There is an increasing need for devices that can be powered for extended periods of time where it is difficult or impossible to maintain or replace, such as pacemakers, long term space flight or undisturbed sensors for military use. Presently, most portable devices run off a Lithium-Iodide battery, which gives a high amount of power but could only last approximately 2 to 5 years, requiring frequent replacement. However, replacement is unnecessary for betavoltaic cells as they can last at least 20 years. City Labs Inc. received a general license for commercially available tritium betavoltaic cells that were validated at extreme temperatures without permanent degradation. To fully determine the effectiveness of a betavoltaic cell, the electrical performance (I-V curves) of three betavoltaics were evaluated while temperatures were ramped up and down from −30°C to 70°C. Short circuit current, open circuit voltage, maximum power and fill factor were used to compare electrical performance. Results indicated that the open-circuit voltage and maximum power decreased as temperature increased, suggesting that betavoltaic cells are suited for cold environments below 0°C, such as during nightfall when a photovoltaic cell may not be used.