Silicon solar cells with front hetero-contact and aluminum alloy back junction

We prototype an alternative n-type monocrystalline silicon (c-Si) solar cell structure that utilizes an n/i-type hydrogenated amorphous silicon (a-Si:H) front hetero-contact and a back p-n junction formed by alloying aluminum (Al) with the n-type Si wafer. Such a structure combines a conventional high-throughput Al-Si alloying process with excellent front surface passivation provided by a-Si:H. A key process consideration is to preserve the clean c-Si front surface through the high-temperature alloying, so there will be effective a-Si:H passivation. From cell simulations, we estimate a front SRV of 10–50 cm/sec has been achieved in our process. The best prototype 1×1 cm² cell with planar front surface and single anti-reflection (AR) coating layer has demonstrated a confirmed conversion efficiency of 13.5%, Voc of 604.7 mV, and fill factor (FF) of 79.9%. Processes for further efficiency improvements are described.