Abstract: A monolithic semiconductor solar cell including a semiconductor layer including a plurality of pores, wherein walls of the pores are doped, forming vertical junctions between the walls of the pores and a bulk of the semiconductor, the pores each contain a conductor which is in electrical contact with the walls of the pores, and the conductors of the pores are electrically interconnected to provide an output voltage of the solar cell. A monolithic semiconductor solar cell including a semiconductor layer including a plurality of trenches, wherein walls of the trenches are doped, forming vertical junctions between the walls of the trenches and a bulk of the semiconductor, the trenches each contain a conductor which is in electrical contact with the walls of the trenches, and the conductors of the trenches are electrically interconnected to provide an output voltage of the solar cell. Related apparatus and methods are also described.