Vibration intensity and Fröhlich electron phonon coupling in halide perovskite CsPbBr3
Résumé
In recent years, 3D inorganic CsPbX3 (X=Cl, Br, I) perovskite materials have gained popularity for their potential in various optoelectronic applications. These materials, especially as quantum dots, offer an attractive platform for classical and quantum light emission, exhibiting high photoluminescence quantum yield, broadband absorption, tunable emission wavelength and high photoluminescence stability[1,2,3]. For example, quantum lasers[4] and quantum computing[5] are considered to be their most promising applications. However, the precise nature of the coupling between electrons and phonons in 3D CsPbX3 perovskite materials remains unclear. This effect has potential to affect fundamental optoelectronic properties, including carrier mobility and excitonic effects. To access the electron phonon interaction, studying the lattice vibrations is the first step. We choose CsPbBr3 as a typical material in our study due to its wide range of applications in quantum dots. To measure the lattice vibrations, we carry out coherent inelastic neutron scattering experiments. Well-defined optical phonon bundles are measured in CsPbBr3. In order to further study the electron phonon coupling especially for optical phonons, we carry out first-principles calculations. Based on our simulation parameters, we calculate the electron phonon interaction strengths using the Fröhlich model as CsPbBr3 is a strong polar semiconductor. In addition, the disordered structure is introduced to take into account the strong anharmonicity of this material[6]. The dominant optical mode of CsPbBr3 is approximately 20 meV, which is consistent with temperature broadening of photoluminescence spectra and Raman scattering measurements reported for CsPbBr3 quantum dots[7,8]. These results provide support for our ongoing theoretical studies on carrier-phonon interactions in disordered structures and excitonic polaron effects.