Investigation of the stability of metallic grids for large-area perovskite solar cells

Metal contacts are an extremely important part of photovoltaic devices, since they might decrease device stability, or underperform in their function of current extraction. In the case of perovskite solar cells, the metallic component has been less investigated than other cell components, either in the back (rear) contact, or in the form of grid collectors in the front contact. The interaction between the perovskite layer and the metal contact is of utmost importance, since it has been demonstrated for gold and silver (most used metals in perovskite cells) that degradation processes might derive from unwanted contacts between the metal and the perovskite components. Herein, we present a systematic investigation of a series of metals typically used in the electronic or photovoltaic industries (Ag, Al, Au, Cu, Mo, Ni, Pd, Pt, and Ta) in order to assess their stability towards the processing steps of a typical perovskite cell assembly, and also when direct contact between the perovskite and the metal layer takes place. By assessing the morphological and electrical properties of the metal layer after performing a variety of tests, we observed that only four of those metals maintained their integrity. Based on the results, we point out which metal is expected to be most suitable one, from an industrial point of view, and to enable long-term device operation.