Chromium Cluster Luminescence: Advancing Near‐Infrared Light‐Emitting Diode Design for Next‐Generation Broadband Compact Light Sources

Abstract In modern technology devices, an energy‐saving miniature near‐infrared (NIR) light source plays a critical role in non‐destructive, non‐invasive sensing applications and further advancement of technology. This paper reports the broadband NIR luminescence of Cr³⁺ clusters for designing phosphor‐converted NIR light‐emitting diodes as an alternative to typical isolated Cr³⁺ centers and Cr³⁺ ion pairs. Here, Cr³⁺ clusters form in the intermediate spinel structure of MgGa₂O₄ by utilizing the long‐chain edge‐shared octahedral dimers with the shortest bond distance between Cr³⁺ cations. Electron paramagnetic and magnetometry measurements confirm the isolated Cr³⁺ and Cr³⁺ clusters, resulting in NIR luminescence with three distinct emission centers. The formation of Cr³⁺ clusters in MgGa₂O₄ ensures stable internal quantum efficiency (≈94%), full‐width‐half‐maximum (248 nm), thermal stability (87%), and a radiant flux of ≈17.66 mW. This work offers a promising approach to NIR phosphor design and enhances the understanding of luminescence mechanisms in spinel and related structures.