NOVELTY - The cell (1000) has sub-cells (500a-500c) provided with different band gap energy. One of the sub-cells comprises a n-type semiconductive graphene stacked on a p-type semiconductive graphene. The different band gap energy decreases in the sub-cells distal from incident electromagnetic radiation. A transparent conductive substrate (300) is in contact with each sub-cell. An anti-reflective coating (50) and a metal contact (55) are formed at a surface closest to a light source. The n-type semiconductive graphene is doped with nitrogen or phosphorus.    USE - Graphene-based multijunction flexible thin-film solar cell e.g. triple-junction graphene photo cell and ten-junction graphene photo cell, for converting light to electricity.    ADVANTAGE - The cell allows thickness of the cell to be decreased from hundreds of microns to less then a hundred microns thick so as to reduce production cost of the cell. The cell is deposited on cheap flexible substrates e.g. plastic or polymers, such that difficulties in handling and installation can be reduced. The cell allows efficiency of the cell to be increased by connecting multiple cells with different band gaps in series. The cell utilizes a sub-cell component of the semiconducting graphenes that comprise monoatomic graphene layers so as to increase incident photons absorption and to reduce thermalization loss.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for making a graphene-based multi-junction flexible thin-film solar cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a triple-junction graphene solar cell made of three components of semiconducting graphene with different band gaps that are stacked on top of each other and separated by transparent conductive and flexible substrates.    Anti-reflective coating (50)    Metal contact (55)    Transparent conductive substrate (300)    Sub-cells (500a-500c)    Graphene-based multijunction flexible thin-film solar cell (1000)