Consider a piece of photovoltaic.

a) Sketch its layout, showing the two regions of different doping, identifying where the light is focused on it, which way the electrons move, where there are regions of local net electric charge, and where there are regions with significant electric field. In regard to the regions of net charge, show which region is positive and which negative, and identify which species (electrons, ions, holes) accounts for the charge. Explain all your choices.

b) What physical property of the semiconducting material determines the maximum volt- age that can be produced? Suppose you wished to combine several separate photovoltaic elements in order to achieve a higher voltage; how would you connect them?

c) An electrical supply can be characterized by, among other properties, its voltage and its frequency. What must be done to the electricity generated by photovoltaics in order to make its voltage and frequency match those of the US grid, i.e., 110V rms and 60 Hz AC?