Bifacial Solar Cells on Multi-Crystalline Silicon with Boron BSF and Open Rear Contact

The standard industrial multi-crystalline silicon (mc-Si) solar cell is monofacial and includes screen printed aluminum back surface field (BSF). A simple approach to increase performance and reduce costs per W_peak is to collect the albedo on the rear side. In this work a bifacial, screen printed mc-Si solar cell with boron BSF is demonstrated. Rear to front efficiency ratios of up to 0.83 have been reached on 100times100mm² mc-Si wafers with a thickness of about 200mum. The best solar cell processed so far with a boron BSF had an efficiency under front side illumination of eta=16.1% and a back to front efficiency ratio of 0.77. The possible gain in performance in later operation was estimated using PC1D simulation and depends on the albedo that is the amount of light that penetrates into the solar cell from the rear side. The simulation was confirmed by outside module tests, leading to an average gain of 19.5% over one day