Weak light effect in multicrystalline silicon solar cells

Abstract

Minority carrier trapping centers frequently exist in solar grade multicrystalline silicon, such trapping centers cause a drastic increase in photoconductance at carrier injection levels equal to and below the trap density, this phenomenon leads to higher open circuit voltage for multicrystalline silicon solar cells at illumination levels below about 0.2 suns compared to high performance crystalline silicon solar cells. In this paper, the open circuit voltage of multicrystalline silicon solar cells are investigated at low illumination levels, the experiments prove that some multicrystalline silicon solar cells which have higher trap density have higher open circuit voltage at weak illumination levels, and have lower efficiency, so a new method is presented to analyze quality of multicrystalline silicon by measuring open circuit voltage at weak illumination levels in-line, this makes cells manufacturers gain insight into the quality of multicrystalline silicon wafer from different multicrystalline silicon manufacturers easily with the same cell process before screenprinting and firing.