Polarized Electroluminescence Emission in High-Performance Quantum Rod Light-Emitting Diodes via the Langmuir-Blodgett Technique.

Due to their anisotropic structure, quantum rods (QRs) feature unique properties that differ from quantum dots, such as suppression of non-radiative Auger recombination and linearly polarized light emission. Despite many potential advantages, the progress of QR-based light-emitting diodes (QR-LEDs) is left behind due to the difficulty in aligning QRs. In this study, polarized electroluminescence emission is reported in high-performance QR-LEDs by employing the Langmuir-Blodgett (LB) technique. The adoption of the LB technique successfully produces a highly dense and smooth QR film with a high degree of alignment. As a result, the aligned QR films exhibit polarized photoluminescence emission with a degree of linear polarization of 2.1. Advantageous features of the LB technique, such as nondestructiveness, precise thickness control, and the nonnecessity of an additional matrix material, allow to fabricate QR-LEDs with the same procedure as the standard spin coating-based scheme. The device is fabricated via the LB technique, which shows excellent device performance, such as the low turn-on voltage of 1.8 V, peak luminance of 56 287 cd m-2 , and peak external quantum efficiency (EQE) of 10.33%. Furthermore, these devices clearly exhibit an indication of polarized electroluminescence emission, which opens new opportunities for QRs in display technologies.