Molecular structure and excitation characteristics of DHR under different external electric fields

Abstract

Dicycloheptarubicene (DHR) is a new organic P-type semiconductor material. In this paper, the B3LYP/ 6-311G (d,p) method of density Functional Theory (DFT) was used to optimize the geometric structure of DHR molecule. On this basis, the same method and basis group are used to calculate and analyze the effects of applying different electric fields (0–0.025a.u.) along the X-axis on the geometric structure, energy, dipole moment and molecular infrared spectrum of DHR molecule. Then, the WB97XD/ DEF2-TZVP method of time-dependent density Functional Theory (TD-DFT) was used to calculate the first 20 excited states of DHR molecules under different electric fields, and the main excited states were analyzed by hole-electron analysis. Finally, the effect of applied electric field on the hole mobility of DHR was investigated by calculating the frontier orbital energy levels. The results show that: DHR molecule exhibits strong vibration Stark effect under different external electric fields. With the appearance of red shift or blue shift, the molar absorption coefficient of the molecule is also redistributed. The applied electric field can change the electron excitation characteristics and excitation types of DHR molecules. When F = 0.025 a.u., the excited states of S0-S1 and S0-S13 change from highly local π → π* excitation to π → σ* charge transfer excitation. The external electric field can change the hole transfer rate by changing the HOMO energy level of DHR molecule. When F > 0.025a.u., the hole transfer rate of DHR molecule will exceed 0.082 cm2·v-1·s−1. This provides theoretical basis for designing DHR molecules as organic semiconductors in the future.