The generation of electricity through solar energy stands out as one of the fastest-growing renewable energy sources worldwide. The global demand for energy, coupled with the rising levels of CO2 in the atmosphere, highlights the need to develop renewable sources of energy. The current challenge of utilizing photovoltaic cells for electricity production lies in the efficiency of the photovoltaic conversion process occurring within the device. To enhance the efficiency of photovoltaic devices, scientists have been investigating light conversion processes to improve radiation absorption and conversion. The study and application of the downconversion process with luminescent materials have been explored to prevent energy loss in solar devices. Zinc Oxide nanoparticles (ZnO NPs) have been employed for this purpose due to their favorable optical properties for downconversion applications. Organic–inorganic perovskites, such as methylammonium lead iodide perovskite (CH3NH3PbI3), have shown promising results for power conversion efficiency, and the present study aimed to assess the increased efficiency of perovskite devices with the addition of ZnO nanoparticles on top of the device. Such optical improvement in the device can occur because high-energy photons, which would be absorbed by layers such as glass and ITO, which are not semiconductors and do not generate charge carriers, will now be absorbed by the ZnO NPs and emitted at longer wavelengths. These longer wavelengths will be absorbed in the active layer of the device, thus generating charge carriers. The obtained results demonstrated that ZnO nanoparticles with approximately 45 nm diameter can successfully produce a downconversion process, leading to improved light absorption by the active layer of the cell and consequently improving photovoltaic efficiency of a perovskite device by 5.5 %.