OPTIMUM GRID-LINE PATTERNS FOR CONCENTRATOR SOLAR-CELLS UNDER NONUNIFORM ILLUMINATION

An optimization procedure for obtaining solar cell grid patterns is presented which minimizes the combined power loss from grid resistance, emitter-layer resistance, and grid shading. The approach is specifically tailored to describe concentrator cells by including the possibility of nonuniform illumination and assuming that a low-loss bus bar encircles the cell. The model generated is quasi-one-dimensional, assuming that all relevant cell parameters, including the illumination profile, can be described as functions of a single dimensional variable. Other significant assumptions include independence of the three loss mechanisms, a uniform grid thickness which is limited by the smallest line width present, and a uniform emitter sheet resistance. The resulting expressions can be solved iteratively by computer, though for small cells under uniform illumination an approximate analytical solution is possible.