Potential of chemical rounding for the performance enhancement of pyramid textured p-type emitters and bifacial n-PERT Si cells

Abstract

We have investigated the effects of chemical rounding (CR) on the surface passivation and/or antireflection performance of AlOx- and AlOx/SiNx:H stack-passivated pyramid textured p(+) -emitters with two different boron doping concentrations, and on the performance of bifacial n-PERT Si solar cells with a front pyramid textured p(+)-emitter. From experimental results, we found that chemical rounding markedly enhances the passivation performance of AlOx layers on pyramid textured p(+)-emitters, and the level of performance enhancement strongly depends on boron doping concentration. Meanwhile, chemical rounding increases solar-weighted reflectance (R-SW) from similar to 2.5 to similar to 3.7% for the AlOx/SiNx:H stack-passivated pyramid textured p(+)-emitters after 200-sec chemical rounding. Consequently, compared to non-rounded bifacial n-PERT Si cells, the short circuit current density Jsc of 200-sec-rounded bifacial n-PERT Si cells with similar to 60 and similar to 100 Omega/sq p(+) -emitters is reduced by 0.8 and 0.6 mA/cm(2), respectively under front p(+)-emitter side illumination. However, the loss in the short circuit current density JSC is fully offset by the increased fill factor FF by 0.8 and 1.5% for the 200-sec-rounded cells with similar to 60 and similar to 100 Omega/sq p(+)-emitters, respectively. In particular, the cell efficiency of the 200-sec-rounded cells with a similar to 100 Omega/sq p(+)-emitter is enhanced as a result, compared to that of the non-rounded cells. Based on our results, it could be expected that the cell efficiency of bifacial n-PERT Si cells would be improved without additional complicated and costly processes if chemical rounding and boron doping processes can be properly optimized.