Effects of non-4f states on Pr³⁺ luminescence in phosphors

Different emission wavelengths of Pr³⁺ ion, from the ultraviolet to the infrared, may result from the effects of non-4f states in phosphors. Such non-4f states generally refer to the Pr³⁺ 4f5d state, exciton-like state or charge-transfer state. Here, we present a brief review on Pr³⁺ luminescence by the means of emission spectral measurement in several representative phosphors. Several interesting spectral phenomena are reported and reviewed, including the effects of impurity-trapped exciton state and charge-transfer state on the luminescence quenching in the Pr³⁺-activated phosphors. We expect this review is beneficial to the readers to better understand their experimental findings, and to inspire them to design new and improved phosphor systems.