Al<inf>0.52</inf>In<inf>0.48</inf>P ⁵⁵Fe x-ray-photovoltaic battery

An Al0.52In0.48P 55Fe radioisotope microbattery is demonstrated over the temperature range -20 °C to 160 °C. Al0.52In0.48P p+-i-n+ mesa structures were used to collect the photons from a 238 MBq 55Fe radioisotope x-ray source. The effects of temperature on the key microbattery parameters were studied. Increasing the temperature, the saturation current increased; whilst the open circuit voltage, the maximum power and the conversion efficiency decreased. An open circuit voltage of 0.97 V and a conversion efficiency of 22% were measured in a single p+-i-n+ mesa structure at -20 °C. The highest total microbattery maximum output power using two mesa structures was 1.2 pW at -20 °C.