A solar cell includes polysilicon P-type and N-type doped regions on a backside (106) of a substrate (103), such as a silicon wafer. A trench structure (104) separates the P-type doped region (101) from the N-type doped region (102). Each of the P-type and N-type doped regions may be formed over a thin dielectric layer (113). The trench structure (104) may include a textured surface (114) for increased solar radiation collection. Among other advantages, the resulting structure increases efficiency by providing isolation between adjacent P-type and N-type doped regions, thereby preventing recombination in a space charge region where the doped regions would have touched.