Cr3+↔Fe3+ Energy Transfer Offset Enabling Anti‐Thermal Quenching Near‐Infrared Emission for Coded Wireless‐Communication Applications

Abstract Broadband near‐infrared (NIR) emission phosphors are crucial for the construction of next‐generation smart lighting sources; however, the thermal quenching (TQ) issue poses a significant challenge to their applications. In this study, anti‐TQ NIR emission is demonstrated in hexafluoride phosphors, using a facile Cr 3+ /Fe 3+ co‐doping strategy. Owing to the controlled forward resonance energy transfer (ET) from Cr 3+ to Fe 3+ and one‐phonon‐assisted back ET from Fe 3+ to Cr 3+ , the thermally enhanced broadband NIR luminescence is realised in series of fluoride such as Na 3 FeF 6 :Cr 3+ , Na 3 GaF 6 :Cr 3+ , Fe 3+ , K 2 NaScF 6 :Cr 3+ , Fe 3+ , etc. By varying the chemical composition of the phosphor, the anti‐TQ emission is achieved even upon raising the temperature to ≈423 K. The anti‐TQ luminescence mechanism is investigated, and the ET offset effect on luminescence TQ is demonstrated. More importantly, by combining these phosphors with blue InGaN chip, anti‐/zero‐TQ NIR light emitting diodes with a high photoelectric conversion efficiency even up to 19.13%@20 mA are further fabricated to realize the emerging coded optical wireless‐communication applications. These findings can initiate the exploration of NIR phosphors with anti‐TQ luminescence properties for advanced optoelectronic applications.