Small-Area Si Photovoltaics for Low-Flux Infrared Energy Harvesting

Silicon photovoltaics are prospective candidates to power mm-scale implantable devices. These applications require excellent performance for small-area cells under low-flux illumination condition, which is not commonly achieved for silicon cells due to shunt leakage and recombination losses. Small area (1-10 mm
²
) silicon photovoltaic cells are studied in this paper, where performance improvements are demonstrated using a surface n-type doped emitter and Si
₃
N
₄
passivation. A power conversion efficiency of more than 17% is achieved for 660-nW/mm
²
illumination at 850 nm. The silicon cells demonstrate improved power conversionefficiencyand reduced degradation under low illumination conditions in comparison with conventional crystalline silicon photovoltaic cells available commercially.