Rod-Shaped Nanographenes as Emitters in Fluorescent OLEDs

Abstract

A significant challenge in the field of organic light-emitting diodes (OLEDs) technology is the development of stable, cost-effective, and sustainable emitters. Current emitters are frequently based on rare metals and heteroatom-based chromophores. Carbon-based nanomaterials, such as carbon dots (CDs) or nanographenes (NGs), offer a promising alternative due to their high photoluminescence quantum yields, the abundance of carbon materials, and the versatility of their syntheses. In this work, we fabricated green-light-emitting electroluminescent devices containing C₆₀-tBu₈ nanographene acting as the emitter. This nanographene contains 60 sp² carbon atoms and tert-butyl solubilizing group on the periphery; it was synthesized via the bottom-up approach. The C₆₀-tBu₈ was fully characterized, and it was incorporated into the emissive layer of a benchmark OLED stack (ITO/PEDOT:PSS/NG-containing active layer/BCP/TmPyPB/LiF/Al). The OLED devices containing the C₆₀-tBu₈ exhibited current and power efficiencies (CE and PE) of 2.27 cd·A^–1, 0.28 lm·W^–1 and luminance of 164 cd·m^–2. The performance remains modest in comparison to state-of-the-art OLEDs, but it outperforms previous attempts to utilize nanographenes as active materials for fluorescent OLEDs. Following the initial results, we also tested two other NGs (C₇₈-tBu₆ and C₉₆-tBu₈), which contain 78 and 96 sp² carbon atoms as fluorescent emitters in OLEDs. The objective was to fine-tune the electroluminescence to yellow-orange and red light.