Hole transporting material 5, 10, 15-tribenzyl-5H-diindolo3, 2-a:3',2'-c-carbazole for efficient optoelectronic applications as an active layer

In order to explore the novel application of the transparent hole-transporting material 5,10,15-tribenzyl-5H-diindolo3,2-a:3',2'-c-carbazole (TBDI), in this article TBDI is used as an active layer but not a buffer layer in a photodetector (PD), organic light-emitting diode (OLED), and organic photovoltaic cell (OPV) for the first time. Firstly, the absorption and emission spectra of a blend layer comprised of TBDI and electron-transporting material bis-(2-methyl-8-quinolinate) 4-phenylphenolate (BAlq) are investigated. Based on the absorption properties, an organic PD with a peak absorption at 320 nm is fabricated, and a relatively-high detectivity of 2.44×10¹¹ cm·Hz^1/2/W under 320-nm illumination is obtained. The TBDI/tris (8-hydroxyquinoline) aluminum (Alq₃) OLED device exhibits a comparable external quantum efficiency and current efficiency to a traditional 4, 4-bisN-(1-naphthyl)-N-phenyl-aminobiphenyl (α-NPD)/Alq₃ OLED. A C₇₀-based Schottky junction with 5 wt%-TBDI yields a power conversion efficiency of 5.0%, which is much higher than 1.7% for an α -NPD-based junction in the same configuration. These results suggest that TBDI has some promising properties which are in favor of the hole-transporting in Schottky junctions with a low-concentration donor.