Design of lanthanide-based OLEDs with remarkable circularly polarized electroluminescence

Organic Light-Emitting diodes (OLEDs) able to directly emit circularly polarized (CP) electroluminescence (CP OLEDs) are gaining much interest, due to their possible applications in anti glaring screens, 3D displays and in medical diagnosis. We have recently demonstrated that chiral lanthanide complexes can be employed in solution processed CP OLEDs, obtaining highly CP emission [1]. Here, we present a strategy to improve devices efficiency both in terms of external quantum efficiency and degree of polarization of emitted photons, based on the optimization of the active layer formulation and devices architecture [2]. In this way, 75 % of emitted photons at 595 nm are circularly polarized with an EQE enhanced by one order of magnitude with respect to our earlier proof-of-concept prototype. Moreover, by comparing experimental data and a modeling the main factors affecting polarization inside such devices are identified: the position of the recombination zone allied with the reflection on the cathode plays a major role on the polarization outcomes. The development of devices embedding other classes of chiral emitters can be envisaged to possibly bring the organic chiral photonic technology to the next readiness level.