NOVELTY - The method involves forming an active cell on a tunnel junction (142A) with first and second semiconductor layers, and forming a contact layer (134) overlying an active region using a multi-junction contact pattern compatible with silicon based solar module process. A wafer form multi-junction photovoltaic device i.e. multi-junction solar cell (100), is provided in the silicon based solar module process. The multi-junction photovoltaic device is used in the silicon based solar module process. A module including the multi-junction photovoltaic device is output using the pattern.    USE - Method for fabricating a multi-junction monolithically integrated semiconductor-based photovoltaic device i.e. multi-junction or triple junction solar photovoltaic cell, and single junction solar cell using a silicon-cell and module production compatible process for converting light energy into electrical energy.    ADVANTAGE - The method enables enhancing ability to manufacture solar cells with relaxed design tolerances and simplified fabrication techniques, while offering a wide range of high efficiency and reducing dollar-per-watt cost of solar cells. The method enables fabricating the solar cell to lattice-match a silicon substrate of another cell so as to reduce possibility of generating structural defects i.e. misfit dislocations, which degrade optoelectronic quality of subsequent semiconductor layers. The method enables defining multiple portions of the solar cell such that overall efficiency of the solar cell is increased or maximized, while reducing and minimizing device thickness and associated fabrication cost. The method enables providing additional flexibility to produce an optimal tunnel junction with respect to an overall photovoltaic design to provide better tradeoff between absorption and low resistance.    DETAILED DESCRIPTION - The semiconductor layers are carbon doped layers.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a multi-junction solar cell.    Multi-junction solar cell (100)    Base (102)    Nucleation layer (106)    Contact layer (134)    Tunnel junctions (142A, 142B)