Metastability in boron-doped multicrystalline silicon wafers and solar cells

Metastability of boron-doped multicrystalline silicon wafers and solar cells under illumination has been investigated. Lifetimes of boron-doped multicrystalline silicon wafer degrade very rapidly within the first 30 min under 1 sun illumination to about 40% of its initial values. Carrier lifetime distribution maps show that high lifetime regions degraded more than lower regions. The same tendency of rapid degradation is observed in B-doped conventional cast multicrystalline silicon solar cells where short circuit current, open circuit voltage and efficiency degrade very rapidly by only 3% within few minutes of illumination. Possibilities of elimination of light-induced degradation by means of using gallium as dopant instead of boron are investigated. Carrier lifetimes of Ga-doped wafers show certain stability under illumination. The same stability is found in Ga-doped solar cells.