>24% Efficient Tunnel Back Contacted polyZEBRA Solar Cells

The polyZEBRA tunnel back contact technology is a low-cost solar cell concept, which utilizes industrially established equipment only. In particular, the patterning of both polarities on the rear side is done with commercially available lasers. A recent cell batch achieved a solar cell efficiency mean value of 24.0% with a certified champion efficiency of 24.12%. The next steps for efficiency improvements of the polyZEBRA technology are explored in an experiment-based simulation. Actual measured values from improved test structures are used as input parameters for the iterative simulation study. This includes reduced recombination currents at the surface of the gap and front side region as well as in the (p) poly-Si/SiOx emitter region, the increase of the emitter coverage ratio and the reduction of the recombination at the metal contacts. Under the assumptions that these improvements will soon be implemented in the process flow, a short-term efficiency potential of >25% was estimated.