SrHfO3:Cr3+ Perovskite Microcubes for Rare-Earth-Free NIR-I Light Emission

Near-infrared (NIR)-emitting phosphors are in high demand owing to their application in areas of high importance, such as security, night-surveillance, imaging, storage, and optoelectronics. However, to achieve high success in these applications, wide broadband NIR emissions are needed and, in that context, the crystalline field of the host matrix plays a very important role. In this work, we have achieved a broad NIR emission in the range of 700-1000 nm in hydrothermally synthesized SrHfO3:Cr3+ (SHOC). SHO assumes a microcrystalline cube morphology, and chromium doping make it more and more symmetric, and the particle size increases with doping. Broadband NIR emissions have been ascribed to the stabilization of Cr3+ in a strong crystalline field of HfO6 octahedra. X-ray photoelectron spectroscopy supported this by confirming the formation of oxygen vacancies in all the samples. The shorter lifetime (similar to 13-44 mu s) is attributed to chromium ions situated in close vicinity to oxygen vacancies at distance X, whereas the longer-lived (similar to 56-127 mu s) originate from chromium ions situated at a long distance from oxygen vacancies at distance Y, and Y is greater than X. Positron annihilation lifetime spectroscopy suggested an increase in defect concentration with doping, which causes concentration quenching beyond 2.0 mol% endowed by multipolar interactions. This work culminates the very important role of defects, local site, and doping on efficient NIR light emissions from a perovskite lattice.