Bifacial Multicrystalline Solar Cells with Efficiencies above 18% Prepared in an Industrial Production Environment

31st European Photovoltaic Solar Energy Conference and Exhibition; 355-358
RCT Solutions GmbH developed its PERCT process for application on standard multi crystalline ptype wafer material as a cost effective alternative to the common AlOx based PERC technology. The PERCT cell architecture is based on a “passivated emitter rear totally diffused (PERT)” cell design. The totally diffused BSF is realized by a fast and cost effective BBr3 boron diffusion step in a standard diffusion tube furnace - prior to the back side passivation and protection by a PECVD SiN. No AlOx is used. A unique feature of this technology, enabled by the conductivity of the boron-diffused layer, is the option to prepare bifacial multi crystalline solar cells with a screen printed finger grid on the rear side. Particularly for mc-Si the availability of processes for the preparation of bifacial cells is very limited. In this paper we report about the latest results from trials in industrial production lines with both cell types – single facial and bifacial PERCT, but with a focus on bifacial cells. While the bifacial solar cell type was for the first time processed in a purely industrial environment, the trials with the single facial cells were continued with further improved efficiencies. Additionally the cost analysis of mc-Si bifacial solar cells has been refined and shows the lowest system cost compared to other bifacial solar cell types. For the single facial PERCT cells a top average efficiency of 18.7% and a 19.0% maximum efficiency for best cells was obtained. Bifacial solar cells reached a top average efficiency of 18.3% and a maximum efficiency of 18.6% (rear side 15.3%) measured on a conventional black chuck.