c-Si wafer-equivalent epitaxial thin-film solar cells on isolating substrates

A new cell concept has been developed that enables epitaxial c-Si thin-film solar cells to be made using isolating substrates. The Recrystallised Wafer-Equivalent on an Isolating Substrate (RexWISe) cell concept relies on an array of mini-silicon rods through the substrate to enable standard contacting. Processing techniques have been developed to produce the rods by drilling holes through the substrate, coating the holes with an intermediate layer, filling the holes with a seeding layer deposition and then recrystallising the seeding layer. Subsequently, the active layers of the cell are epitaxially grown onto the recrystallised layer and then this “Wafer-Equivalent” structure is metallised like a standard wafer solar cell. The first solar cells have been produced to test the RexWISe process and a “proof-of-concept” efficiency of almost 8% was achieved.