Micromachined Flexible Semi-Transparent Silicon Solar Cells as Power Sources for Microsystems

We are reporting the fabrication and test of ultrathin, flexible semi-transparent single-crystal solar cells using a silicon undercut microfabrication techniques suitable for powering up exposed biomedical microsystems. The resulting cells are 15 micrometers thick. The solar cells provide a short circuit current density of 0.54 mA cm
^-2
and the open circuit voltage of 340 mV under low indoor lighting (13 mW.cm
^-2
) conditions achieving an average light transmission of ~25%.