Design optimization for higher stabilized efficiency and reduced light-induced degradation in boron-doped Czochralski silicon solar cells

Traditional boron-doped Czochralski-grown Si solar cells are known to suffer from light-induced degradation (LID). By replacing B with Ga as the dopant in the Cz melt or by reducing the oxygen content by implementing the magnetic-Cz (MCz) growth technique, not only can LID be eliminated, but also higher efficiency manufacturable screen-printed cells can be achieved. The use of thinner wafers for cell fabrication can significantly reduce the impact of LID on conventional boron-doped Q cells. Knowledge of the degraded cell parameters can be used to determine the optimal thickness for the highest stabilized efficiency. A methodology is developed to maximize the stabilized efficiency after LID by using thinner wafers. A combination of device modeling and experimental data is used to demonstrate that, for traditional B-doped Q Si, which degraded from 75 to 20 mus, the optimum cell thickness is in the range of 150-190 mum for a back-surface recombination velocity of similar to 10(4) cm/s. This cell design reduces the material cost and the absolute efficiency degradation from 0.75% (375 mum device) to 0.24% (157 pm device) and gives the highest stabilized Cz cell efficiency. Copyright 2002 John Wiley Sons, Ltd.