GaAs-Based Photovoltaic Infrared Energy Harvesting for Microscale Biomedical Implants

Fully wireless biomedical implantable devices at the microscale are of great interest for a new generation of medical devices inlcluding precision health and brain computer interfaces. One of the greatest challenges for these devices is energy harvesting for self-powering at small dimensions. Here, we demonstrate a dual-junction (DJ) GaAs-based photovoltaic (PV) cell with an area of $200 \times 200 \mu \mathrm{m}^2$ and explore their energy harvesting potential for near surface bio-implantables. The devices achieve a power conversion efficiency of more than 23% and open circuit voltage of greater than 1.13 V under $1.03 \mu \mathrm{W}/\mathrm{mm}^2$ near-infrared irradiation at a wavelength of 850 nm. Energy harvesting through biospecimens of mouse skins are demonstrated with sufficient power density for low power CMOS electronics at irradiance levels orders of magnitude below the maximum permissible exposure defined by the American National Standards Institute (ANSI) Z136.1 standard.