Europium-Doped CsPbBr ₃ Epitaxial Films: Fabrication, Optical and Electrical Properties, and High-Performance Photodetectors

To modulate the optical and electrical properties of quasi-intrinsic CsPbBr 3 epitaxial films, europium bromide (EuBr 3 ) is introduced as a heterovalent dopant source, and europium-doped CsPbBr 3 (CsPbBr 3:Eu) films are epitaxially grown on (100)-oriented SrTiO 3 substrates via pulsed laser deposition (PLD). By X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS) analyses, we demonstrate that Eu 3+ ions incorporate into the lattices of CsPbBr 3 epitaxial films and partially substitute for B-site Pb 2+ . Temperature-dependent photoluminescence (TDPL) studies reveal the optical signatures of Eu-induced donor defects in the CsPbBr 3:Eu films, with a donor-bound exciton (D 0 X) emission peak being clearly identified. Ultraviolet photoelectron spectroscopy (UPS) and Hall results demonstrate that the conductive type of epitaxial films changes from quasi-intrinsic to obvious N-type after Eu 3+ doping. Moreover, Eu 3+ doping also remarkably reduced the trap density and enhanced the film conductivity. As a result, the CsPbBr 3:Eu film photodetector achieves a responsivity nearly five times that of its undoped device, along with an increase in detectivity from 8.91 × 10 12 to 4.17 × 10 13 Jones. The epitaxial film photodetectors without encapsulation show good long-term stability in ambient air. Our work demonstrates that heterovalent doping is a viable strategy for modulating the semiconductor properties of CsPbBr 3 epitaxial films, offering a valuable idea for designing high-performance photoelectric devices.