LeTID sensitivity of gallium- & boron-doped Cz-Si PERC solar cells with an average conversion efficiency of 23.6 %

Within this work, both the performance and reliability of industrial Boron- and Gallium-doped p-type monocrystalline silicon solar cells with dielectrically passivated rear side with an average conversion efficiency of 23.6 % are investigated. Currently, in the p-type wafer market, mainly Gallium-doped material is available. Only a few studies on the so-called “Light and elevated Temperature Induced Degradation” (LeTID) of this material are available in literature. It is advertised that the well-known degradation effect caused by boron-oxygen can be avoided by using gallium as dopant. This work shows that, if not adequately suppressed, LeTID can also occur in Gallium-doped p-type Czochralski silicon passivated emitter and rear solar cells with a degradation in cell and module output power of up to 3 %_rel., which cannot be significantly suppressed in a straightforward manner by conventional processing steps to permanently deactivate the light- induced degradation defect. We demonstrate the possibility to reduce LeTID significantly on Boron- and Gallium-doped p-type monocrystalline solar cells and modules by adapting the cell process and processing sequence.