Secondary Ion Mass Spectrometry of Silicon Photovoltaic Cells: Impacts of Pyramidal Surface Texture

Chemical characterization of the thin passivation layers on commercial silicon photovoltaic (PV) cells is essential to understand and improve device performance and reliability. However, characterization methods are complicated by surface texture, which can cause shadowing and artefacts. Secondary ion mass spectrometry (SIMS) is an important tool for depth profiling silicon passivation layers due to its high chemical sensitivity enabling detection of hydrogen. Hydrogen concentration and migration is an important topic for reliability of silicon PV, especially for newer cell types such as the silicon heterojunction (SHJ) modules studied here. In these studies, we demonstrate the orientation of pyramidal surface texture with respect to the SIMS ion beam, and we give examples of different SIMS profiles on the same sample that depend on the angles (θ) between the ion beam and (111) pyramidal face as well as (α) between the ion beam and the (100) direction normal to the sample surface.