Abstract
Phosphole-based systems due to the unique electronic and optical properties have recently been paid much attention as optoelectronic materials. In this work, the relationship among the electronic structure, charge injection, and transport was investigated for five derivatives of dithieno[3,2-b:2',3'-d]phosphole (systems 1-5). The structures of systems 1-5 in the ground (S-0) and the lowest singlet excited (S-1) states were optimized at the HF/6-31G* and CIS/6-31G* levels of theory, respectively. Based on these structures, electronic spectra were calculated by time-dependent density functional theory. The simulated emission peaks of five phosphole derivatives locating at the blue-green region (448-516 nm), are in good agreement with the experimental data. Compared with tris-(8-quinolinolate) aluminum (III) (Alq(3)), normally used as an excellent electron transporter, systems 1-5 show a significant improvement in electron affinity (EA) due to sigma*-IEuro* hyperconjugation, which can effectively promote ability of electron injection. The small differences between lambda (h) and lambda (e) for systems 1-5 (0.06-0.14 eV) facilitate charge transfer balance, which suggests systems 1-5 can act as potential ambipolar materials. Owing to good rigidity, low-lying LUMO levels, delocalized frontier molecular orbitals, and the small reorganization energies, the five derivatives of dithieno[3,2-b:2',3'-d]phosphole are expected to be high-efficiency blue materials in single-layer OLEDs.