Susceptibility to environmental factors, such as moisture, humidity, oxygen, heat, and ultraviolet (UV) light (photoinstability), has affected perovskite solar cell (PSC) stability in practical applications. To overcome the instability and performance degradation due to oxygen, humidity, and moisture, different strategies and encapsulation schemes have been proposed, and promising results have been obtained. However, photostability remains a major hurdle because UV light is an inherent part of the standard incident spectrum of PSCs. To prevent photoinstability and increase quantum energy harvesting levels, cadmium chalcogenide (CC) photoluminescent (PL) filters for downconverting the UV part of the incident spectra obtained for PSCs are proposed in this work. The concept was illustrated by matching 500-nm-thick CC-PL filters to the front glass of a PSC to form a CC-PL/glass/indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)/perovskite/Ag structure. Cadmium sulfide (CdS), cadmium selenide, and cadmium telluride were taken as the CC materials. Practical measurements confirmed that the PSC with the CdS-PL filter can maintain 92% of its initial value under continuous light soaking for more than 100 h. Furthermore, this PSC exhibited the best improvement in power conversion efficiency.