Abstract:

The influence of introduction of chlorine and long alkyl side chains on the hole transport properties of indolo[3,2-b]carbazole derivatives was investigated by combining density functional theory(DFT) with Marcus theory in hopping regime. The results show that the introduction of chlorine atoms induces more delocalized HOMO of 2,8-dichloro-indolo[3,2-b]carbazole(2) and 2,8-dichloro-5,11-dihexyl-indole[3,2-b]carbazole(3) than indolo[3,2-b]carbazole(1), while the LUMO is just the opposite. Besides, both the HOMO/LUMO energy levels and the reorganization energies of compounds 2 and 3 are lower than those of compound 1, and the former is ascribed to chlorine exerting conjugate effect to HOMO but electron-withdrawing effect to LUMO. With the introduction of both chlorine and long alkyl side chains on indolo[3,2-b]carbazole derivatives, compound 3 has higher mobility, which is the result of denser intermolecular packing of dimer A in compound 3 than compounds 1 and 2, thus larger electronic coupling and higher the mobility are measured for compound 3. The results obtained from the band model are consistent with those calculated by hopping regime. Finally, our calculation clarify again in theory that rational chemical modification can improve the carrier transport property of indolo[3,2-b]carbazole derivatives.

Key words: Indolo[3,2-b]carbazole derivative, Transport material, Carrier transport, Density functional theory, Band model