Benzo[b]selenophene/thieno[3,2-b]indole-Based N,S,Se-Heteroacenes for Hole-Transporting Layers

Two series of new N,S,Se-heteroacenes, namely, 6H-benzo[4',S' selenopheno[2',3':4,5]thieno[3,2-b]indoles and 12H-benzo[4 '',5 '']selenopheno[2 '',3 '':4',5']thieno[2',3'4,5]thieno[3,2-b]indoles, were successfully obtained using an effective strategy based on Fiesselmann thiophene and Fischer indole synthesis. The new molecules exhibit a large optical band gap (2.82 eV < E-g(opt) < 3.23 eV) and their highest occupied molecular orbital (HOMO) energy formed by the plane pi-core ranges between -5.2 and -5.6 eV, with the narrower optical band gap and lower HOMO level corresponding to selenated heteroacenes. In thin solid films of the heteroacenes, hole mobility measured using the conventional CELIV technique ranges between 10(-5) and 10(-4) cm(2).V-1, s(-1). All these make the proposed condensed-ring compounds a promising platform for the development of hole-transporting materials applicable in organic electronics.