The Institute for Solar Energy Research Hamelin (ISFH) and the Leibniz Universität Hannover claim to have achieved an efficiency of 26.1 per cent for a crystalline silicon solar cell-based p-type wafer material at the laboratory level. This is a world record for p-type silicon and a European record for crystalline silicon, the two entities stated. The measurement was conducted by ISFH-CalTeC at its ISO 17025-accredited calibration and test centre.
The p-type cells currently available in the market achieve an efficiency of 21-22 per cent, if combined with PERC cell technology. The record efficiency for such cells is 23.4 per cent while the record for p-type laboratory cells was recently set at around 25 per cent.
The record cell uses a passivating electron-selective n±type polysilicon on oxide (POLO) junction at the minus contact of the cell and a hole-selective p±type POLO junction at the plus contact, the research institute stated. The high selectivity of these junctions would be responsible for the higher efficiency, as they are applied in an inter-digitated pattern on the rear side, thus minimising the parasitic absorption in the poly-Si, and avoiding shading by front side metallisation.
The ISFH plans to replace the process steps with industry-related process steps in the coming years. The goal is the integration of the POLO junctions into the current mainstream technology. Germany’s Federal Ministry of Economy and the State of Lower Saxony have financially backed the research.