Circularly polarized luminescence and electroluminescence in thin films of novel chiral π-conjugated oligomers

The development of chiral organic semiconductors with high dissymmetry factors glum in thin films, which could be employed as active layers in very innovative technological applications such as circularly-polarized organic light-emitting diodes (CP-OLEDs), is a fundamental research goal. Recently, we reported a family of structurally related benzo[1,2-b:4,5- b’]dithiophene and 1,4-phenylene-based oligothiophenes, studying their electronic circular dichroism (ECD) properties in thin films [1-3]; unfortunately, all these compounds revealed very low luminescence intensity in the solid state, due to aggregation-induced quenching phenomena. Here we describe a set of new structurally related 1,4-phenylene and 9Hcarbazole- based oligothiophenes (Figure 1). Circularly polarized luminescence (CPL) features revealed quite large dissymmetry factors glum values (in the order of 10-2) on a wide wavelengths range, originating from their chiral supramolecular organization in thin film state. In light of the encouraging results, we investigated their electroluminescence (EL) and circularly polarized electroluminescence (CPEL) in organic light-emitting diodes: a multilayer CP-OLED device with dissymmetry factor |gEL| values up to 5.4·10-2 was obtained, which represents to the best of our knowledge the first example of CP-OLEDs based on chiral oligothiophenes as the organic semiconductor.