Transferring the record p-type Si POLO-IBC cell technology towards an industrial level
Felix Haase1, Christina Hollemann1, Soeren Schaefer1, Jan Kruegener2,3, Rolf Brendel1,3,4, Robby Peibst1,2
1Institute for Solar Energy Research in Hamelin (ISFH), Emmerthal, Germany
/2Institute of Electronic Materials and Devices, Leibniz Universitaet Hannover, Hannover, Germany
/3Laboratory of Nano and Quantum Engineering (LNQE), Leibniz Universitaet Hannover, Hannover, Germany
/4Institute for Solid State Physics, Leibniz Universitaet Hannover, Hannover, Germany

First, we evaluate the efficiency potential of our technology on p-type (B) Cz wafers using the lab-type process. We present a p-type Cz Si solar cell with an implied pseudo efficiency of 25.2 % measured before metallization. We had to reduce the thermal budget and to address the following implications: The two doped poly-Si on oxide (POLO) passivating contacts at the rear side are separated by a region of initially intrinsic (i) poly-Si. The latter is at least partially doped by lateral in-diffusion of dopants during junction formation. With increasing width of the (i) poly-Si region, the recombination at the p(i)n diode in the poly-Si decreases whereas the recombination at the (i) poly-Si/c-Si surface increases due to the bad passivation quality of the intrinsic poly-Si. As a second step, we suggest a process sequence for reducing the complexity down to that of a conventional PERC cell. This approach utilizes the Al‑BSF - a major strength of the existing p-PERC cells - and eliminates its weakness - that is the efficiency limiting emitter recombination at the front contacts - by using a POLO passivating contact. The process uses the same tools as a p-PERC cell and only adds one tool for poly-Si deposition. Our finite element simulations shows, that such a solar cell can reach an efficiency of 24.7 %