A distributed emitter model for solar cells: Extracting an equivalent lumped series resistance

Front-surface grid electrodes are employed in solar concentrator cells to reduce the power losses resulting from lateral current flow in the cell emitter. Because these electrodes also shadow the cell from a portion of the incident light, an optimal grid electrode layout must be determined for a particular cell design. A useful model for this optimization in the early stages of design is to simulate the distributed losses in the cell emitter using an equivalent lumped series resistance. Previously reported 1D analytical calculations showed that the equivalent resistance of one square should simply be one-third of the emitter sheet resistance. However, this calculation ignores local biasing loss. In this work, a quasi-3D model, which includes this local biasing effect, is used to extract an equivalent series resistance of a section of the emitter between grid electrodes for various sheet resistances and optical concentration.