Researchers at UC Berkeley have infected tobacco plants with a genetically engineered virus to produce artificial photovoltaic and photochemical cells, chromophores, which they claim can be extracted and dissolved into a solution to create spray on solar cells. In theory they can be sprayed onto a coated glass or plastic substrate, then electricity can be harvested.This method is more environmentally friendly than traditional methods of making solar cells and could lead to cheap, temporary and biodegradable solar cells. The tobacco plants are harvested and chopped up to extract the structures.

Francis Research Group, UC Berkeley
According to the Francis Research Group at the Department of Chemistry UC Berkeley, lead by Professor Matt Francis, "The protein coat of the tobacco mosaic virus (TMV) has been explored extensively for the construction of nanoscale architectures. This protein can be produced in very high yield through E. coli expression and self-assembles into light harvesting rods that are much like those assembled from the wild-type protein." Tobacco mosaic virus has a rod like appearance and causes characteristic patterns or mottling and discolouration of tobacco leaves.

Tobacco leaf with mosaic virus, source Grasscity
Electricity has not yet been harvested using this method, and unlike silicon, this manufacturing process of solar cells is not quite efficient and the cells would not last as long as silicon, but it could act as a transportable, cheap and temporary biodegradable power source.
Top image of tobacco crop, source Bunda College
For more read : Energy Harvesting and Storage for Electronic Devices 2009-2019