Bright single-active layer small-molecular organic light-emitting diodes with a polytetrafluoroethylene barrier

Single-layer organic light-emitting diodes (OLEDs) with a small molecule, tris(8-hydroxyquinoline) aluminum $({\mathrm{Alq}}_3)$ as the only active material, have been prepared. In order to achieve an efficient hole injection, a thin layer of polytetrafluoroethylene (Teflon) was inserted between the anode and the ${\mathrm{Alq}}_3$ layer. The effect of the Teflon layer thickness upon the device performance has also been investigated. A brightness of 16 000 cd/m² with 6 nm thick Teflon layer was achieved, whereas the conventional double-layer OLEDs with ${\mathrm{N,N}}^{\prime }$ -bis-(1-naphthyl)-${\mathrm{N,N}}^{\prime }$ -diphenyl-${\text{1,1}}^{\prime }$ biphenyl ${\text{4,4}}^{\prime }$ -diamine and ${\mathrm{Alq}}_3$ showed only 9500 cd/m² in our experiments. The single-layer structure technology is of great importance to the OLED’s commercialization due to its possible lower cost and higher production efficiency. And it is reasonable to infer that, based on this work, higher device performance could be realized by screening both the active material and the barrier layer material.