Solar cells have been manufactured already for a long from inexpensive materials with different printing techniques. Especially organic solar cells and dye-sensitized solar cells are suitable for printing.-We wanted to take the idea of printed solar cells even further, and see if their materials could be inkjet-printed as pictures and text like traditional printing inks, tells University Lecturer Janne Halme.When light is absorbed in an ordinary ink, it generates heat. A photovoltaic ink, however, coverts part of that energy to electricity. The darker the color, the more electricity is produced, because the human eye is most sensitive to that part of the solar radiation spectrum which has highest energy density. The most efficient solar cell is therefore pitch-black.