A similar issue is solved in technologies like solar panels (or even the "nighttime anti-solar panels" The Debrief previously reported) by connecting a number of separate solar cells in a single circuit, creating a whole panel of cells that can accumulate more energy collectively. Unfortunately, the "coupling capacitance" that occurs between the upper and lower electrodes of each cell prevents this from working for individual raindrop power collection cells. Because of the excessive power loss from cell to cell as a result, it seems hard to construct a full-fledged rain panel.
The team claims to have finally settled on what they believe to be the best design for making rain panels a workable substitute for or addition to solar panels. Making each cell function independently and determining the ideal surface thickness specifically appeared to lower the coupling capacitance to a level that made power collecting from rain panels feasible.