Chiral thiophene-based oligomers with remarkable circularly polarized luminescence and electroluminescence in thin films

In recent years, circularly polarized luminescence (CPL) spectroscopy has acquired considerable interest in organic optoelectronics.1 A fundamental research goal is the development of chiral organic semiconductors showing high dissymmetry factor glum values in thin films, which can be employed as active layers in technological applications such as circularly-polarized organic light-emitting diodes (CP-OLEDs). We reported the synthesis of 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: we discovered that these compounds can generate a manifold of situations, with the dichroic signals due to the sum of true circular dichroism contribution (i.e. CDiso), related to the intrinsic chirality of the supramolecular aggregates, which is invariant upon sample orientation, and the interference between linear dichroism (LD) and linear birefringence (LB), termed LDLB, arising at a higher hierarchical level.2 Unfortunately, all these compounds revealed very low luminescence intensity in thin films due to aggregation-induced quenching phenomena.