High quality kerfless silicon mono-crystalline wafers and cells by high throughput epitaxial growth

Abstract

Crystalline silicon based photovoltaics continues to be the dominant technology for large scale deployment of solar energy. While impressive cost gains in silicon based PV have come with scale, there remains a strong push for increased efficiencies and further lowering of manufacturing costs to achieve true grid parity. So far, however, there has not been a production proven approach that reduces the cost while maintaining or increasing the efficiency. Attempts to reduce the amount of silicon used, for example, have led to development of various kerfless wafer manufacturing approaches. While some of these approaches have shown the potential for reduced costs, they also compromise the efficiency mainly due to the inferior quality of the material.Epitaxy based kerfless silicon wafers, on the other hand, has shown the potential to reverse this trend offering lower manufacturing costs while maintaining or even enhancing the efficiency due to the high quality of the n-type and p-type silicon epitaxial (Epi) wafers. In this work, we present key aspects of Crystal Solar’s patented high throughput production silicon epitaxial reactor and its use in the manufacture of standard thickness N and P wafers. Besides the advantage of having significantly reduced cost, these Epi wafers have high quality, better mechanical strength and resistance to light inducted degradation due to significantly reduced oxygen content.

Dislocation-limited performance of advanced solar cells determined by TCAD modeling

“…We assume this relatively high lifetime in order to determine limiting efficiencies solely due to the presence of dislocations. We also note that lifetimes this high have been reported in several materials that have significantly higher dislocation density than CZ-Si, including epi-Si [23,24], QSC-Si [25], n-type mc-Si [8], and silicon grown by the so-called "noncontact-crucible method" [26,27]. While p-type mc-Si has not yet achieved wafer-averaged millisecond lifetimes, lifetime has increased dramatically in recent years and is now approaching 1 ms [28].…”

Simplified cleaning for 22.5% nPERT solar cells with rear epitaxial emitters

“…In the past years, silicon epitaxial technology received a lot of research attention in the photovoltaic community because it has the potential for growing large-area silicon wafers directly from the gas phase without kerf losses (no wafer slicing required) [1,2] as well as the potential to be used for the growth of highly doped layers (e.g. emitters) with doping profiles and thickness uniformity tailored down to nanometer scale [3][4][5][6].…”