Towards light-trapping free amorphous Si only multi-junction solar cells

We propose a thin film solar cell structure that enables ultrathin film absorber application and single material multi-junction structure. This proposal is targeting amorphous Si only multi-junction solar cells on a patterned transparent electrode, which might perform high light harvesting efficiency and high output voltage at the same time. In addition, photon management of this proposed structure does not rely on traditional light trapping scheme but rather on lateral collection scheme with `sidewall solar cells'. To implement the proposed solar cells, a suitable process sequence is suggested, where a challenging node separation process between sidewall solar cells is included. In this work, we present a-Si solar cell on patterned TCO without node separation. We found the signature of absorption path elongation by sidewall solar cells, which is one of the essential principles of our proposed solar cell. This proposal would provide a promising route to a high performance and low cost a-Si only photovoltaics.