Bright blue-emitting Ce3+ complexes with encapsulating polybenzimidazole tripodal ligands as potential electroluminescent devices.

Electronic transitions in luminescent molecules or centers in crystals couple to vibrations. This results in broadening of absorption and emission bands, as well as in the occurence of a Stokes shift EStokes. In principle, one can derive from EStokes the Huang–Rhys parameter S, which describes the microscopic details of the vibrational coupling and can be related to the equilibrium position offset ΔQe between the ground state and excited state. The commonly used textbook relations EStokes = (2S − 1)ℏω and EStokes = 2Sℏω are only approximately valid. In this paper we investigate how EStokes is related to S, taking into account the effects of a finite temperature. We show that in different ranges of temperature, different approximate relations between EStokes and S are appropriate. Moreover, we demonstrate that the difference between the barycenters of absorption and emission bands can be used to determine S in an unambiguous way. The position of the barycenter is, contrary to the Stokes shift, unaffected by temperature.

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Resolving the ambiguity in the relation between Stokes shift and Huang–Rhys parameter

Relationship of Stokes shift with composition and structure in Ce3+/Eu2+-doped inorganic compounds

The absorption, excitation, and emission spectra of the Sr2CeO4 nanocrystals prepared by the modified sol–gel method were investigated. The impact of the average grain size of Sr2CeO4 nanocrystals on their optical properties was investigated. It was observed that with increasing the average grain size of Sr2CeO4 nanocrystals, the emission decay times decreased significantly. A similar behavior was observed for the emission quantum efficiencies and the Huang–Rhys factors. The grain size dependence of optical parameters of Sr2CeO4 nanocrystals was found well fitted by functions of the reciprocal of the grain diameter. It was shown that this dependence may be rationalized assuming that the correction for electric local field associated with effective refractive index affecting the spherical nanoparticle is governed by its shell.

Influence of grain size on optical properties of Sr2CeO4 nanocrystals.

Synthesis of novel Eu2+ activated K3Ca2(SO4)3F down-conversion phosphor for near UV excited white light emitting diode

Photoluminescence and electron-vibrational interaction in 4fn−15d states of Ce3+ or Pr3+ ions doped LnBO3 (Ln=Lu, Y, La) orthoborates materials

Emission and excitation spectra of the Ce3+ ion in LuF3 single crystal were measured at 77 K. The broad bands observed in these spectra were attributed to the parity-allowed electric-dipole 4f ← 5d transitions within Ce3+ ion. No zero-phonon lines were observed, which is indicative of a strong electron-phonon coupling in this host. It is shown that Ce3+ 5d excited configuration splits into five crystal-field components in LuF3. The influence of the crystalline environment on the position of the lowest Ce3+ 5d level is investigated. The energy of the lowest level of the 4f N −15d excited configuration was predicted for all the trivalent rare earth ions embedded in LuF3. Positions of crystal field spitting levels of 4f N −15d configuration relative to the host electronic bands were discussed.

O. Krachni

Papers

Photoluminescence and electron-vibrational interaction in 4fn−15d states of Ce3+ or Pr3+ ions doped LnBO3 (Ln=Lu, Y, La) orthoborates materials

The 4f-5d luminescence transitions in cerium-doped LuF3