A subcutaneously implantable power supply is a device for powering implantable medical devices. The device has one or more thin photovoltaic cells contained in a case formed of a lamination of a plurality of thin plastic layers. Each layer is translucent in the area covering said cell, such that the power supply is sufficiently flexible to conform to body contours. The device is lightweight, flexible, has improved sealability, and has improved internal battery longevity.