The performance of hybrid organic perovskite (HOP) for solar energy conversion is driving a renewed interest in their light emitting properties. The recent observation of broad visible emission in ...layered HOP highlights their potential as white-light emitters. Improvement of the efficiency of the material requires a better understanding of its photophysical properties. We present in-depth experimental investigations of white-light (WL) emission in thin films of the (C6H11NH3)2PbBr4. The broadband, strongly Stokes shifted emission presents a maximum at 90 K when excited at 3.815 eV, and below this temperature coexists with an excitonic edge emission. X-rays and calorimetry measurements exclude the existence of a phase transition as an origin of the thermal behavior of the WL luminescence. The free excitonic emission quenches at low temperature, despite a binding energy estimated to 280 meV. Time-resolved photoluminescence spectroscopy reveals the multicomponent nature of the broad emission. We analyzed the dependence of these components as a function of temperature and excitation energy. The results are consistent with the existence of self-trapped states. The quenching of the free exciton and the thermal evolution of the WL luminescence decay time are explained by the existence of an energy barrier against self-trapping, estimated to ∼10 meV.
We synthetize some new perovskite thin layers: p-fluorophenethylamine tetraiodoplumbate pFC(6)H(4)C(2)H(4)NH(3))(2)PbI(4) perovskite molecules, included in a PMMA matrix. We report on the optical ...properties of the perovskite doped PMMA thin layers and we show that these layers are much more stable under laser illumination and present a smaller roughness than the spin-coated (C(6)H(5)C(2)H(4)NH(3))(2)PbI(4) layers. These new layers are used as the active material in vertical microcavities and the strong-coupling regime is evidenced by a clear anti-crossing appearing in the angular-resolved reflectivity experiments at room temperature.
We have realized Perot–Fabry microcavities containing a twodimensional layered perovskite-type semiconductor: (C6H5C2H4–NH3)2PbI4 between a dielectric mirror and a metallic mirror. A strong coupling ...regime between the perovskite exciton and the confined photon mode has been evidenced at room temperature from angular-resolved reflectivity experiments, anticrossings as large as 190 meV are observed between the excitonic and cavity modes. We have shown that the design of the microcavity can be varied at will, so that the detuning or the Rabi splitting can be precisely chosen. The emission of the polaritonic low energy branch has been observed.
Density Functional Theory is used to study the vibrational properties of 2H-PbI2 semiconductor. The Born charge tensors are determined. Calculated phonon frequencies at the Brillouin zone center are ...compared to Raman scattering and IR absorption measurements. The computed Raman spectra show a good agreement with available experimental data. The simulated phonon dispersion curves are compared with triple-axis neutron scattering measurements.
► Symmetry properties of the optical phonons of the 2H-PbI2 crystal are analysed. ► Born charges and the dynamical matrix are calculated the Brillouin zone center. ► Raman spectra and Phonon dispersion have been compared with experimental results. ► Dielectric tensors are calculated and compared to measurements.
The performance of hybrid organic perovskite (HOP) for solar energy conversion is driving a renewed interest in their light emitting properties. The recent observation of broad visible emission in ...layered HOP highlights their potential as white-light emitters. Improvement of the efficiency of the material requires a better understanding of its photophysical properties. We present in-depth experimental investigations of white-light (WL) emission in thin films of the (C6H11NH3)(2)PbBr4. The broadband, strongly Stokes shifted emission presents a maximum at 90 K when excited at 3.815 eV, and below this temperature coexists with an excitonic edge emission. X-rays and calorimetry measurements exclude the existence of a phase transition as an origin of the thermal behavior of the WL luminescence. The free excitonic emission quenches at low temperature, despite a binding energy estimated to 280 meV. Time-resolved photoluminescence spectroscopy reveals the multicomponent nature of the broad emission. We analyzed the dependence of these components as a function of temperature and excitation energy. The results are consistent with the existence of self-trapped states. The quenching of the free exciton and the thermal evolution of the WL luminescence decay time are explained by the existence of an energy barrier against self-trapping, estimated to similar to 10 meV.
The molecular crystal of
(
C
6
H
5
C
2
H
4
–
NH
3
)
2
PbCl
4
perovskite presents an excitonic state with an absorption energy in the ultraviolet range (3.64
eV, 341
nm) and a large binding energy ...(few hundred of meV). We report here on the realization of a Pérot–Fabry
λ
-microcavity containing a thin film of this material as active layer. Angle-resolved reflectivity and photoluminescence measurements demonstrate this microcavity works, at room temperature, in the strong coupling regime: the cavity photon mode and the excitonic state are not eigenmodes of the system any more, the new eigenmodes are a linear and coherent superposition of the exciton and photon states, called cavity polaritons.
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