TRANSPARENT GRAPHENE ANODES FOR ORGANIC LIGHT EMITTING DIODES

2021-7-14
Sharif, Parisa
This thesis presents a novel method for fabrication of OLEDs on a specific flexible PET substrate with graphene anodes, demonstrating low sheet resistance, high work function, and an extremely high luminance. Firstly, a single-layer graphene growth process with chemical vapor deposition (CVD) method is optimized. Flexible anodes are then fabricated by stacking 7-layers of graphene films and doped with nitric acid to reduce the sheet resistance. Modified few layer graphene anodes by 29 Ω/□ sheet resistance and 84% transparency are used to fabricate OLEDs with a new family of thermally activated delayed fluorescence (TADF) materials. Observation of TADF in conjugated systems redefined the molecular design approach to realize highly efficient OLEDs in the early 2010s. Enabling effective reverse intersystem crossing (RISC) by minimizing the difference between singlet and triplet excited state energies (ΔEST) has been proven to be a widely applicable and fruitful approach, which resulted in the unproduction of numerous OLED devices with remarkable external quantum efficiencies (EQE). Here, a new series of TADF materials (SeTADFs) with heavy-atom selenium is used as emitters in OLED structure. One of these materials, SeDF-B, resulted in pure blue emission with EQEs approaching 26%. Additionally, flexible graphene-based electrodes were developed for OLEDs vi and revealed similar performance with indium tin oxide (ITO) on glass in most cases while, remarkably, suppressing ITO/Glass in pure blue OLED devices. These devices highlight the first-ever TADF based OLEDs that utilize graphene-based anodes in the literature.

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Citation Formats
P. Sharif, “TRANSPARENT GRAPHENE ANODES FOR ORGANIC LIGHT EMITTING DIODES,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.