Extrinsic Photoluminescence and Resonant Raman Spectra of CsPb₂Br₅ Microspheres

Abstract

Tetragonal CsPb2Br5 has attracted tremendous attention due to its high stability and strong green emission. But its luminescence mechanism has become controversial after it was found to have an indirect band gap of 3.35 eV. Here, the phase structure of a sample is confirmed by its X-ray diffraction pattern and absorption spectrum. The mechanism of the green emission is investigated by its temperature evolution features and the resonant Raman signals. The emission wavelength and its large-scale blue shift with increasing temperature from 10 to 300 K agree well with that of perovskite CsPbBr3, while the theoretical calculation indicates a negligible shift for the optical emission in CsPb2Br5. The photoluminescence intensity, peak width, and temporal decay curves also exhibit a temperature dependence similar to that of CsPbBr3. Additionally, the phonon modes derived from the resonant Raman spectrum of the sample are the same as those found in CsPbBr3 nanocubes. The one at 30 cm–1 is thought to be a specific sign for the existence of CsPbBr3. Therefore, the green emission observed in CsPb2Br5 is proposed to be from the traces of perovskite CsPbBr3.

Soft crystal lattice and large anharmonicity facilitate the self-trapped excitonic emission in ultrathin 2D nanoplates of RbPb2Br5

“…S11b, ESI) exhibits an absorption edge at ∼3.54 eV which is consistent with the previous reports. 9,62 . The PL spectrum of bulk CsPb 2 Br 5 polycrystals (Fig.…”

“…S11b, ESI †) exhibits an absorption edge at $3.54 eV which is consistent with the previous reports. 9,62 The PL spectrum of bulk CsPb 2 Br 5 polycrystals (Fig. S11d, ESI †) revealed a narrow emission centred at 550 nm when excited at 350 and 380 nm.…”

“…S11d, ESI†) revealed a narrow emission centred at 550 nm when excited at 350 and 380 nm. 62,63 The narrow emission line for CsPb 2 Br 5 in comparison to that for RbPb 2 Br 5 might be ascribed to the suppression of electron–phonon coupling in CsPb 2 Br 5 . 64 Thus, by changing only the A cation in between 2D [Pb 2 Br 5 ] − polyhedral units, the nature of PL emission varied immensely and subsequently, this exciting observation needs further detailed investigations.…”

Photoelectrochemical performance of ligand-free CsPb2Br5 perovskites

“…13 However, to date, no one has reported the photoelectrochemical properties of CsPb 2 X 5 perovskite synthesized in a pure water phase. 14,15 Thus, it is imperative to develop new strategies for the synthesis of water-stable perovskites that allow them to maintain their good charge transportability while extending their applicability to photoelectronics and related applications. In this study, we developed a pure-water-phase synthesis strategy for ligand-free 2D cesium lead halide perovskite CsPb 2 X 5 nanoplatelets, and the photoelectrochemical performance of CsPb 2 Br 5 nanoplatelets was evaluated and preliminarily explored.…”

“…13 However, to date, no one has reported the photoelectrochemical properties of CsPb 2 X 5 perovskite synthesized in a pure water phase. 14,15…”