Development of 40 μm thin flexible silicon heterojunction solar cells

Large-scale production of flexible solar cells is paving the way to portable, low cost power devices. Whereas energy conversion of commercial devices is in the range of 5-15 %, our goal is to manufacture low cost, flexible solar cells with efficiencies over 20%. In this paper we present our latest development on flexible silicon heterojunction solar cells using 40 μm thin silicon wafers. Currently, sputtering induces surface damage which leads to an open circuit voltage drop of 15-20 mV when compared to implied open circuit voltages. The degradation of minority carrier lifetime after sputtering can be mitigated, from a maximum of 38% down to 17%, through a 70% reduction in the DC plasma power, thereby increasing the reliability of the process. We experimentally demonstrate average minority carrier lifetimes over 1300 μs and iV _OC over 760 mV for 40 μm thin wafers.