Effects of grain boundaries on cell performance of poly-silicon thin film solar cells by 2-D simulation

The effect of grain boundaries on the performance of poly-Si thin film solar cells was studied theoretically using a 2-D simulation assuming the presence of either rectangular-shaped or graded width grain boundaries in the i-layer of p/i/n structure of solar cells. The grain boundary had an adverse effect mainly on Voc. Jsc gradually increased and saturated with increasing solar cell thickness in cells without grain boundaries, whereas it reached a maximum for an i-layer thickness of 5 μm in polycrystalline silicon cells. The calculation using the graded width model showed that the efficiency of the p+/p−/n+ structure was better than that of the p+/n−/n+ structure. A slight p-type doping of the i-layer was found to be effective in improving cell performance.