Infrared Detection in Perovskite Solar Cells Enhanced by NaYGdF ₄ :Yb ³⁺ , Er ³⁺ Up‐Conversion Nanoparticles

Perovskite solar cells (PSCs), originally developed for low‐cost photovoltaic energy harvesting, can also serve as versatile platforms for photodetection. However, their intrinsic absorption edge below 800 nm prevents direct response to most of the near‐infrared (NIR) spectrum. Here, we demonstrate that integrating up‐conversion (UC) nanoparticles (NaY 65 Gd 15 F 4 :Yb 18 3+ , Er 2 3+ ) enables these devices to function as self‐powered NIR detectors. The nanoparticles, synthesized by a simple hydrothermal route, convert NIR photons into visible emission that matches the perovskite absorption edge. Structural analysis confirmed that particles grown at 220°C with a 15% Gd content crystallize in the hexagonal phase, showing red‐dominated luminescence. Once incorporated into complete perovskite devices, the UC nanoparticles (UCNPs) preserved the baseline photovoltaic response while producing a measurable photocurrent under 980 nm excitation. Our results reveal a practical route to transform PSCs into affordable and scalable devices for infrared sensing.