This work investigates non-rare-earth phosphor (Sr 4 Al 14 O 25 :Mn 4+ , 0.5%Mg) with intensively red luminescence as a luminescent down-shifting layer for perovskite solar cells. The power conversion efficiency of the fabricated device with a structure of NiO/CH 3 NH 3 PbI 3 /[6,6]-phenyl C 61 -butyric acid methyl ester/Au coated with phosphor layer shows a 10% increase as compared with that of the control devices. Importantly, the phosphor layer coating can realize UV-protection as well as

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... erproof capability, achieving a reduced moisture-degradation of CH 3 NH 3 PbI 3 perovskite upon applying an UV irradiation. Therefore, perovskite devices using this luminescent coating show a combined enhancement in both UV downshifting conversion and long term stability. This can be expanded as a promising encapsulation technique in the perovskite solar cell community. A significant progress has been achieved over the past few years for the development of solar cells using hybrid lead halide perovskite as next generation light harvester. 1-4 Currently, the certified power conversion efficiency (PCE) for the perovskite solar cells is dramatically increased over 22.1% for the lab-scale devices. 5 In addition to the high PCE, the perovskite solar cells take advantages of low cost and solution processability, making them as a promising photovoltaic technology till date. 6,7 At present, excellent solar cell performance has been achieved for devices based on inorganic-organic hybrid lead perovskites. However, a number of obstacles limit its commercialization, including long-term device stability in operation conditions with oxygen, humidity/rain/ice, heat, and ultra-violet (UV) light exposure. Previous works have pointed