Silicon Heterojunction Solar Cells on Quasi-mono Wafers

We applied hydrogen passivation, gettering and a combination of both to quasi-mono (qm) wafer material to enhance its bulk lifetime and prepared silicon heterojunction (SHJ) solar cells. We find that while our applied hydrogen passivation alone seems not to enhance lifetime, a gettering treatment increases bulk lifetime so that efficiencies up to 21.5% were achieved with a SHJ solar cell. This is close to the highest efficiency reported for such a cell. We find that the variation of the absorber thickness plays a minor role for the investigated solar cells and that similar efficiencies could have been obtained for Cz and gettered qm wafers. The latter is mainly due to the fact that the higher efficiency potential of the Cz material could not be fully exploited due to a degradation of surface passivation during the sputtering of the TCO on the cell, which could not be fully recovered in the final annealing step.