While PERC (passivated emitter and rear cell) design is currently the most promising cell design and will account for the majority of solar cells in the near future, IBC design is the option with the highest efficiency suitable for mass production. With the contacts soldered only to the rear of the cell, IBC minimizes shadowing and achieves efficiencies of over 23 percent. But quality assurance for IBC cells is not easy, as they typically display much higher metallization on the contact side. This means that the rear of the wafer is more reflective, making it hard to achieve images for reliable inspection performance. Special IBC processes require greater flexibility to capture the relevant structures and clearly separate the features to inspect.
IBC cells are chemically etched flat on the rear of a solar cell. Together, the different contacts create a smooth rear surface, as the wafer is covered with layers of metal, resistors and soldering areas. Differentiating between different materials and overcoming incorrect detection caused by direct reflection is a major challenge for inspection tools.
