Electronic energy dynamics of photoexcited ternary Zintl phase LiSbTe 2 and the distance estimation between trap sites

Abstract

For newly synthesized ternary Zintl phase LiSbTe 2, absorption, fluorescence, and excitation spectra indicate that it has an E g of 4.46 eV, and there is an absorption band around 300 nm below the band gap and a Stokes-shifted fluorescence band around 390 nm. At both room temperature and 77 K, power dependent steady-state and time-resolved fluorescence studies result in the appearance of another fluorescence band at about 450 and 520 nm. As the photon power increases, the 390 nm band is blue shifted at the saturation stage with the saturation of the 520 nm band as well. Along with fluorescence lifetime data, the results imply that the 390 and 450 nm bands correspond to shallow trapped exciton state and deep self-trapped exciton state originating from lattice distortion, respectively, and the 520 nm band is from the surface trap state coupled to the frozen solvent environment. The upper limit distance between the trap sites corresponding to 390 nm band is estimated to be about 17.6 nm by the dielectric function calculation of the gas phase model.