||Perovskite solar cells have been regarded as one of the most promising photovoltaics due to the rapid growth of efficiency from 3.8% to 22.1%. To further improve the power conversion efficiency (PCE), a concept of frequency conversion has been suggested. On the other hand, their poor stability against UV light and water makes it difficult to withstand outdoor conditions. Therefore, it is important to develop a new system that can enhance both the performance and the stability of the perovskite solar cells. Here, we present a stable and highly emissive Pt(II) complex as a photon down-shifting material for perovskite solar cells. The thin and less-aggregated layer of the compound was fabricated by using the ultrasonic spray deposition method. With this layer, the perovskite solar cells showed the enhanced JSC and PCE, which was corresponding to the increased stability against UV irradiation. Furthermore, the significantly improved humidity-stability for the devices was also observed.