Efficient Low-Cost IBC Solar Cells with a Front Floating Emitter: Structure Optimization and Passivation Layer Study

In this paper, we investigate interdigitated back contact solar cells with the front floating emitter structure systematically by using simulated and experimental methods. By comparing the front floating emitter structure with the front surface field structure, it is found that the efficiency of solar cells with the front surface field structure quickly reduces with the increasing of back surface field width; while solar cells with the front floating emitter structure can have a wider front surface field width range with minimum impact on the cell efficiency. More importantly, solar cells with the front floating emitter structure have a larger fabrication process tolerance, especially for the back surface field width, emitter width, and the bulk resistivity, which means that the fabrication process flow can be simplified and the production cost can be reduced. Based on the above results, large area (156.75 mm x 156.75 mm) interdigitated back contact solar cells with the front floating emitter structure are fabricated by using the simplified process with only one masking step. SiOx:B is used as the passivation layer, which can lead to a higher open circuit voltage and lower surface saturation current density. Finally, an efficiency of 20.39% is achieved for the large area solar cells.