High efficiency screen printed low-medium concentrator silicon solar cells with direct printed 50µm wide fingers

Abstract

Screen printed low to medium concentrator silicon solar cells have potential to drive down the cost of PV since it replaces expensive semiconductor material by less expensive optics while maintaining high efficiency. However, the conventional screen-printed finger width is generally ≥100μm which limits the efficiency under higher concentration. In this paper, we report on the application of 50μm wide fingers fabricated by nScrypt non-contact direct printing technology to resolve this problem Two approaches were used to evaluate the merit of fine line extrusion printed fingers relative to normal screen-printed fingers. First approach involves keeping the metal coverage the same by increasing the number of lines, from 50 to 100, which lowers the series-resistance (Rs) and increases the FF. Second strategy involves keeping the Rs same by decreasing the number of lines, from 100 to 69, or reducing metal coverage which leads to higher Jsc. In this study, conventional screen-printed concentrator cells gave a peak efficiency of 19.2% at ~7 suns and 18.5% at 20 suns. The first strategy raised the peak efficiency to 19.7-20.0% in the range of 5 to 20 suns. The second approach to reducing metal coverage which keeping the same Rs raised the peak efficiency to 20.3% at ~7 suns which decreased gradually to 19.2% at 20 suns. Thus the use of 50μm wide lines can give 0.5 to 1.3% absolute efficiency enhancement in the range of 1-20 suns. These are among the most efficient metal paste printed low to medium concentrator solar silicon cells.