Enhanced Stability of Tin Halide Perovskite Photovoltaics Using a Bathocuproine—Copper Top Electrode

Abstract

Abstract Unencapsulated organo‐tin halide perovskite photovoltaic (PV) devices exhibiting record stability (for organo‐tin perovskite PV devices) when tested under continuous one sun solar illumination in ambient air and under electrical load are reported. This exceptional stability is made possible by the use of a bathocuproine | copper cathode in an inverted device architecture. A series of experiments designed to elucidate the underlying reasons for the high stability show that, compared to conventional silver electrodes, compact copper electrodes are far more resistant to corrosion by I 2 gas (evolved when organo‐tin halide decomposes) and toward adverse morphological evolution and ingress of oxygen and water molecules through the top electrode into the device. The findings of these experiments show that copper should be the metal of choice for the reflective cathode in inverted tin perovskite PVs when the material interfacing the metal interacts strongly with it, enabling compact film formation and a stable interface toward copper diffusion into the adjacent charge transport layer.