But not all the sunlight would be
absorbed by this electrode: light with a wavelength longer than 600 nanometres isn't absorbed by the rust - coloured water in the top cell so would pass through to strike the lower electrode, powering the production of hydrogen.
If the rear
electrode is divided into a number of small picture elements (pixels), then an image can be formed
by applying the appropriate voltage to each region of the display to create a pattern of reflecting and
absorbing regions.