Electron-phonon Interaction And Scattering Rate Of New Carbon Materials

With the continuous development of computational physics,it has become an efficient way to guide the experimentalist fabricating the new structure.For semiconductor materials,electron-phonon interaction determines many important properties of materials,such as optical absorption,Raman spectroscopy,thermalization mechanism of hot carriers,etc.Finding materials with long-lived hot carriers by calculation is considered as one of the most possible ways to design and develop new photovoltaic materials.Here we use density functional theory and many-body perturbation theory plus Wannier interpolation method to study the electron-phonon interaction and its scattering rate related problems in recent theoretically predicted or experimentally successfully synthesized carbon materials.(1)Firstly,we investigated the electron-phonon scattering rate and optical properties containing excitonic effects in T-carbon.The results show that optical phonons and acoustic phonons dominate the scattering near the valence band and conduction band edges,respectively.Furthermore,the relaxation time of the hole(0.5 ps)is longer than that of the electron(0.24 ps)due to the different scattering intensity.We also predict that the mean free paths of the hot hole is up to 80 nm,whereas the mean free paths of the hot electron is only 15 nm,which leads to different extraction range for the hot carriers in T-carbon.Our computed results show that the lifetime of the first dark exciton is 3.4 s while it is 2.8 ns for the first bright exciton.The longer exciton lifetime of the lower energy dark exciton would trap much exciton population and further lower the photoluminescence quantum yield in T-carbon.(2)In addition,we have studied D-carbon,a new three-dimensional carbon material.The results show that optical phonons and acoustic phonons are dominant scattering at the valence band and conduction band edges,the relaxation time of holes(3.5 ps)is larger than electrons(0.12 ps)by more than one order of magnitude,resulting in a much higher mean free paths(400 nm)of hot holes than the mean free paths(5.8 nm)of hot electrons.These studies are the theoretical basis for the potential applications of the above two structures in the field of optoelectronic materials in the future.