Optical Investigation of Broadband White-Light Emission in Self-Assembled Organic–Inorganic Perovskite (C₆H₁₁NH₃)₂PbBr₄

Abstract

ABSTRACT. 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)PbBr4. The broadband, strongly Stokes shifted emission presents a maximum at 90K when excited at 3.815 eV, and below this temperature coexists with an excitonic edge emission.X-rays and calorimetry measurements excludes 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 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.

Pure white-light emitting ultrasmall organic–inorganic hybrid perovskite nanoclusters

“…It is mentioned in the literature that the broad PL emission of 2D perovskite materials generally occurred from self-trapping of excitons or electrons/holes. 10,39,40 This electronic process is different than our proposed mechanism, which involves radiative recombination of excitons at mid-gap trap-states giving our broad PL peak. To unravel the exact mechanism, we performed power dependent excitation PL studies (see Fig.…”

“…Thus, the experimental data do not support the self-trapping of excitons because if this would occur the PL intensity would follow a linear relationship with excitation power. 39,40 Considering that the trap-state concentration in MAPbBr3.8 PNCs is finite and slow to relax, trap-state PL would be expected to saturate at high excitation power, as shown for GaN. 41 Therefore, our results strongly support trap-state-related emission.…”

Benzimidazolium Lead Halide Perovskites: Effects of Anion Substitution and Dimensionality on the Bandgap

“…[8] The transient, photo-induced formation of these self-trapped excitons has been observed to occur on a femtosecond (fs) -timescale and its multicomponent nature has been confirmed by temperature dependent and time-resolved PL measurements. [24][25][26] Note that all compounds studied here show similar levels of distortions of the inorganic sublattice, which is why the observed differences in the PL emission may result from different degrees of lattice "softness" or permanent lattice defects rather than (static) structural distortions.…”

Perovskite Materials for Light‐Emitting Diodes and Lasers

“…As a result of the strong confinement in two dimensions and wide compositional flexibility, these layered perovskites are ideal for light-emitting applications. [18,19,50] Moreover, the binding energy is directly tuned by the number of inorganic layers n in the structure, where n = 1 and n = ∞ represent the "pure" layered vs the 3D perovskite, respectively (Figure 6a). Higher-order layered compounds (A′ 2 A n−1 M n X 3n+2 ) with n = 2, 3, 4, etc.…”

“…[19] Cyclohexylamine-based (C 6 H 11 NH 3 ) 2 PbBr 4 layered perovskites also display broad white-light emission, albeit it at 90 K, with a PL maximum of 2 eV and full-width half-maximum (FWHM) of ≈660 meV. [50] REVIEW Conjugated Systems and Chromophores: Beyond simple amines, layered perovskites have also been formed by larger and more complex molecules, such as conjugated molecules and chromophores. The π-π interactions within and between the molecules strongly influence the ordering (conformation and orientation) between the inorganic layers.…”