Abstract: A system and method are presented for the design and fabrication of arrays of vacuum photodiodes for application to solar power generation. In a preferred embodiment, each photodiode cell comprises a microfabricated enclosure with a hermetically sealed vacuum, an absorptive photocathode, and a transparent anode, wherein the photocathode and the anode are separated by a vacuum gap of less than about 20 micrometers. Light incident on the photocathode through the anode leads to a flux of electrons passing from the photocathode across the vacuum gap to the anode. In a further preferred embodiment, the photocathode is backed by a reflection layer with, e.g., controlled diffuse reflection, thus increasing the efficiency of energy extraction. An array of such cells may be manufactured using automated thin-film deposition and micromachining techniques.