Supramolecular π−π Stacking Pyrene-Functioned Fluorenes: Toward Efficient Solution-Processable Small Molecule Blue and White Organic Light Emitting Diodes

Abstract

In this paper, we described a new category of solution-processible small molecule organic light emitting materials—the pyrene-functioned diarylfluorenes: 2PPPF and DPPPF. In solution, both of the materials show deep blue emission. In film, their emission largely red-shifted due to strong π−π stacking of pyrene groups. 2PPPF, which is quite rigid in molecular structure, bearing only one alkoxyl group, could form smooth film by spin-coating. From the photoluminescence and morphology study, we believe the strong π−π stacking enhanced the film forming ability. 2PPPF is an amorphous blue light emitter, with a Tg over 100 °C and Td over 430 °C. The good thermal stability is comparable to polymeric light emitting materials. The material shows strong aggregated emission with a broad structureless peak at about 460 nm in film. Electroluminescent devices by spin-coating were successfully fabricated. A single-layered device using 2PPPF as the active material shows a turn on voltage of 4.3 V, brightness over 3600 cd/...