Increasing the Voltage Output of a Solar Cell
There are a few boost controllers that run down that low, but in general it's better to have a higher voltage to start with. 0.5V at full tilt is really low, presumably it's designed to be stacked to get a usable voltage.

Here's an example of one of the very low input voltage boost converters. Of course this one doesn't do much current, so it doesn't really fit the bill...