New lightweight photovoltaic modules are being developed for powering high altitude unmanned aerial vehicles (UAVs). Modified low-cost terrestrial solar cell and module technologies are being applied to minimize vehicle cost. New processes were developed for assembling thin solar cells, encapsulant films, and cover films. An innovative by-pass diode mounting approach that uses a solar cell as a heat spreader was devised and tested. Materials and processes will be evaluated through accelerated environmental testing.