NOVELTY - A thin interdigitated backside contact photovoltaic solar cell comprises: (a) a monocrystalline semiconducting principal layer of silicon of a first conductivity type; (b) first finger structures formed on the second principal surface, extending along a first direction, spaced from each other along a perpendicular second direction; and (c) second finger structures formed on the second principal surface extending along the first direction, interdigitated with the first finger structures along the second direction.    USE - The thin interdigitated backside contact photovoltaic solar cell is useful manufacturing solar cell.    ADVANTAGE - The thin interdigitated backside contact photovoltaic solar cell has improved design fabricated on a thicker silicon mother wafer, e.g. the cell may be less than 100 microns, preferably less than 50 microns in thickness while the mother wafer may be 180 microns or greater in thickness. The method allows improved fabrication yields through reduced breakage during processing due to the reduced number of processing steps and new approaches for handling very thin silicon wafers thru various processing operations. It also substantially reduces materials costs by the deposition of active silicon layers on reusable mother wafers. The epitaxial deposition of these layers provides better control of the doping profiles and allows the formation of sharp photovoltaic junctions.    DETAILED DESCRIPTION - A thin interdigitated backside contact photovoltaic solar cell comprises: (a) a monocrystalline semiconducting principal layer of silicon of a first conductivity type having a textured first principal surface on a light receiving side of the solar cell and a planar second principal surface on an opposed side of the base layer; (b) first finger structures formed on the second principal surface, extending along a first direction, spaced from each other along a perpendicular second direction, and each comprising a heavily doped region of silicon of the first conductivity type formed in the principal layer, epitaxial with it, and being more heavily doped than the base layer, and a first metal layer contacting the heavily doped region; and (c) second finger structures formed on the second principal surface extending along the first direction, interdigitated with the first finger structures along the second direction, and each comprising an opposed layer of a second conductivity type, formed on the principal layer, and epitaxial with it to create a P-N junction with the base layer, and a second metal layer contacting the opposed layer and electrically isolated from the first metal layer, where the first and second metal layers form two opposed leads for a load of the solar cell. INDEPENDENT CLAIMS are included for:    (1) a method of fabricating a backside contact solar cell comprising: (a) a first deposition step of epitaxially growing a first film of silicon of a first conductivity type on a porous layer formed in silicon wafer; and (b) a second deposition step of epitaxially growing a second film of silicon of a second conductivity type on the first film to thus forming a P-N junction, while the films are attached to the porous layer, a first forming step of forming first electrical contacts to the first layer and a second forming step of forming second electrical contacts to the second layer; and    (2) a method for fabricating a thin interdigitated backside contact photovoltaic solar cell on a thick wafer comprising: (a) epitaxially growing a first layer of silicon of a first conductivity type on an upper surface of a porous crystalline silicon layer formed on a monocrystalline silicon substrate; (b) epitaxially growing a second layer of silicon on the upper surface of the first layer; (c) forming a first passivation layer on top of the second layer; (d) etching first openings through selected areas of the passivation and second layers; (e) forming contact regions within the second layer which are of the second conductivity type and more heavily doped than the second layer, where the dopant species to form the contact regions is diffused through the first openings; (f) etching second openings surrounding the first openings through the passivation and second layers; (g) depositing a conducting layer; (h) etching the conducting layer to remove portions not overlying the contact regions; and (i) etching second openings through the first passivation layer overlying central areas of the second layer.