Temperature dependence of photoluminescence spectra and dynamics of the red-emitting K2SiF6:Mn4+ phosphor

Investigating and understanding temperature-dependent photoluminescence (PL) properties of inorganic phosphors are of vital importance to optimize their performance and expand their application. Recently, K2SiF4:Mn4+ phosphors have attracted intense attention as a red phosphor candidate for white LED applications because of their extremely narrow emission peaks in the red spectral region. Here, temperature-dependent (20-200 °C) diffuse reflection spectra and steady and transient PL spectra of K2SiF4:Mn4+ were systematically investigated. Both the emission intensities and spectral characteristics of the phosphor showed excellent thermal stability at temperatures from 20 to 150 °C, ensuring its great potential for practical white LED applications. An abnormal PL enhancement was found at elevated temperatures that differed from the thermal quenching behavior of common phosphors and could be attributed to enhanced phonon-assisted radiative transitions at higher temperatures. We further successfully tested and verified that the intensity ratio of anti-Stokes and Stokes emission peaks of Mn4+ ions was sensitive to temperature and followed a Boltzmann-type distribution function very well, making the K2SiF4:Mn4+ phosphor a good candidate for temperature sensing, especially for investigating the thermal distribution of white LEDs.