This study provides a reliable strategy to tune the mechanoluminescent colors by adjusting the weak intermolecular interactions.

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A samarium-based down conversion material was employed to simultaneously improve the device performance and long-term stability of perovskite solar cells.

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The stability of both the perovskite material and the interfacial layer is a key issue toward commercializing perovskite solar cells, due to the detrimental effects of water and oxygen under ambient conditions. Here, we report a solution‐processed organic–inorganic halide perovskite solar cell that employs a bilayer PC61BM/CrOx as the electron transport layer. Use of an additional CrOx interfacial layer can enhance the stability of a device in air without encapsulation by more than 10 times compared to that for a device using only a PC61BM electron transport layer. The device with a CrOx interfacial layer can also improve the power conversion efficiency by 17.5% compared to that using PC61BM only. The improved performance is attributed to the better matching of the energy levels of the active layer with the metal electrode and more effective electron collection when using interfacial CrOx as the bilayer electronic transport layer. It was also found that use of CrOx as a passivating layer could resist the diffusion of water and oxygen into the active layer and prevent the reaction of the metal electrode with the perovskite layer.