Alpha and beta-voltaic silicon devices operated at cryogenic temperatures: An energy source for deep space exploration

Nowadays the interest in deep space exploration is very strong; however, powering devices where sunlight is unavailable is a challenging task. Conventional radioisotope thermoelectric generators are difficult to miniaturize, while low-energy particle voltaic devices lack sufficient power density. In this study, we experimentally investigated the use of state-of-the-art 5 × 5 mm2 silicon pad radiation detectors operated at cryogenic temperatures as high-energy particle voltaic devices. Our results show that operating the detectors at 80 K with 241Am (0.1 mCi) and 90Sr- 90Y (0.8 mCi) radioactive sources results in a maximum electrical power of 100 nW/cm2 and 165 nW/cm2, respectively. These values correspond to 11% and 12% efficiency, which is unprecedented for silicon voltaic devices. Additionally, we found that the device's radiation hardness significantly increases at cryogenic temperatures, consistent with the Lazarus effect. After more than 270 h of continuous irradiation with the 90Sr- 90Y source at 80 K, the device's residual efficiency is as high as 1.8% and remains stable. This efficiency value could be increased by stacking multiple devices together, while passive radiative cooling in space allows reaching cryogenic temperatures without extra power.