Molecular Origin of the Asymmetric Photoluminescence Spectra of CsPbBr₃ at Low Temperature

Abstract

CsPbBr3 has received wide attention due to its superior emission yield and better thermal stability compared to other organic–inorganic lead halide perovskites. In this study, through an interplay of theory and experiments, we investigate the molecular origin of the asymmetric low-temperature photoluminescence spectra of CsPbBr3. We conclude that the origin of this phenomenon lies in a local dipole moment (and the induced Stark effect) due to the preferential localization of Cs+ in either of two off-center positions of the empty space between the surrounding PbBr6 octahedra. With increasing temperature, Cs+ ions are gradually occupying positions closer and closer to the center of the cavities. The gradual loss of ordering in the Cs+ position with increasing temperature is the driving force for the formation of tetragonal-like arrangements within the orthorhombic lattice.

Free and self-trapped exciton emission in perovskite CsPbBr3 microcrystals

“…28,29 In a recent report this phenomenon was attributed to a local dipole moment induced by the off-centre localization of Cs + cations. 30 None of these hypotheses to understand the multiple emission peaks have been conrmed and the occurrence conditions for them have not been explored clearly.…”

A theoretical perspective of the ultrafast transient absorption dynamics of CsPbBr3

“…Among the different lead halide perovskites, [2][3][4][5]7 CsPbBr 3 is especially suited for investigations of the excited state dynamics via transient absorption spectroscopy experiments due to its higher photostability compared to other organic-inorganic lead halide perovskites. 11,[18][19][20][21][22][23][24][25][26] The large band gap of CsPbBr 3 that lies within the range of 2.25-2.36 eV according to measurements performed by different groups, 22,27 prevents direct photovoltaic application, but CsPbBr 3 is instead a promising material for LEDs and laser applications. 9,10,28,29 Although several femtosecond transient absorption spectroscopy measurements have been conducted for MAPbI 3 , MAPbBr 3 , and CsPbBr 3 , 14,15,17,23,24,[30][31][32] the interpretation of the mechanistic origin of the observed features is still under debate.…”

“…Among the different lead halide perovskites, 2 , 3 , 4 , 5 , 7 CsPbBr 3 is especially suited for investigations of the excited state dynamics via transient absorption spectroscopy experiments due to its higher photostability compared to other organic–inorganic lead halide perovskites. 11 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 The large band gap of CsPbBr 3 that lies within the range of 2.25–2.36 eV according to measurements performed by different groups, 22 , 27 prevents direct photovoltaic application, but CsPbBr 3 is instead a promising material for LEDs and laser applications. 9 , 10 , 28 , 29 …”

Tailoring Photoluminescence by Strain-Engineering in Layered Perovskite Flakes

“…Moreover, temperature-dependent photoluminescence measurements show a systematic blueshift when temperature increases (Figure 1c, see Figure S2a,b for peak position, line width and integrated area evolution), similar to the 3D counterpart CsPbBr 3 . 37 Additionally, to exclude phase transition effect in the strain experiments, we checked by temperature-dependent micro-Raman spectroscopy the peak position and line width of the ∼44 cm −1 and ∼70 cm −1 vibrational modes ascribed to the distortion of the [PbBr 6 ] 4− octahedra and translation of Cs + , respectively. 38,39 The monotonous shift toward lower frequency of these Raman modes and their broadening as the temperature increases disregard a phase transition in the temperature range under study (80−300 K) 38,40 (Figure 1d, see Figure S2c,d for Raman spectra, peak position, and line width evolution).…”