Electricity potentially means zero CO2 emissions, and it can be stored and transported easily. In theory the Sun could give us all the energy that we need for our civilization. Either way several plants are motorized solar panels and another example of superior engineering from Nature because they could reach even 100% quantum efficiency while actually the state of the art is near 45%, in the lab.
Plants are normally arranged in different levels of height, and each leaf is like a magnet to the sunlight. Some of them grow really fast thanks to this, and like others of their kingdom, contribute to clean the air so as always Nature acts wisely.
Recent research on the subject claims that this dream of reaching high efficiency in sunlight to electricity is possible using vegetation. Although you could redefine what cheap and expensive is like some groups are doing today, one of the big problems of harvesting sunlight is the considerable inversion. An example is Gemasolar, a solar plant pioneers in 24 hour per day efficiency, almost $420 million, $33 per watt.
The research focuses in to interrupt photosynthesis and get electrons from there, an ambitious project that could lead to a great step. We are going to follow this research and keep you informed!