Epitaxially Grown p-type Silicon Wafers Ready for Cell Efficiencies Exceeding 25%

Combining the advantages of a high-efficiency solar cell concept and a low carbon footprint base material is a promising approach for highly efficient, sustainable, and cost-effective solar cells. In this work, we investigate the suitability of epitaxially grown p-type silicon wafers for solar cells with tunnel oxide passivating contact rear emitter. As a first proof of principle, an efficiency limiting bulk recombination analysis of epitaxially grown p-type silicon wafers deposited on high quality substrates (EpiRef) unveils promising cell efficiency potentials exceeding 25% for three different base resistivities of 3, 14, and 100 Ω cm. To understand the remaining limitations in detail, concentrations of metastable defects Fei, CrB and BO are assessed by lifetime-calibrated photoluminescence imaging and their impact on the overall recombination is evaluated. The EpiRef wafers’ efficiency potential is tracked along the solar cell fabrication process to quantify the impact of high temperature treatments on the material quality. We observe large areas with few structural defects on the wafer featuring lifetimes exceeding 10 ms and an efficiency potential of 25.8% even after exposing the wafer to a thermal oxidation at 1050 °C.