Rational Molecular Design Enables Efficient Blue TADF−OLEDs with Flexible Graphene Substrate

Sharif P., Alemdar E., Ozturk S., Caylan O., Haciefendioglu T., Buke G., ...More

Advanced Functional Materials, vol.32, no.47, 2022 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 32 Issue: 47
  • Publication Date: 2022
  • Doi Number: 10.1002/adfm.202207324
  • Journal Name: Advanced Functional Materials
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Applied Science & Technology Source, Chemical Abstracts Core, Chimica, Communication Abstracts, Compendex, INSPEC, MEDLINE, Metadex, Civil Engineering Abstracts
  • Keywords: 2D materials, blue OLED, flexible OLED, graphene, graphene anodes, heavy atom effect, OLED, TADF, ACTIVATED DELAYED FLUORESCENT, LIGHT-EMITTING-DIODES, LAYER, ELECTROLUMINESCENCE, PHENOTHIAZINE, SINGLET, GROWTH, CHARGE, FILMS
  • Middle East Technical University Affiliated: Yes

Abstract

© 2022 Wiley-VCH GmbH.Observation of thermally activated delayed fluorescence (TADF) in conjugated systems redefined the molecular design approach to realize highly efficient organic light emitting diodes (OLEDs) in the early 2010s. Enabling effective reverse intersystem crossing (RISC) by minimizing the difference between singlet and triplet excited state energies (ΔEST) is proven to be a widely applicable and fruitful approach, which results in remarkable external quantum efficiencies (EQE). The efficacy of RISC in these systems is mainly dictated by the first-order mixing coefficient (λ), which is proportional to spin-orbit coupling (HSO) and inversely proportional to ΔEST. While minimizing ΔEST has been the focus of the OLED community over the last decade, the effect of HSO in these systems is largely overlooked. Here, molecular systems with increased HSO are designed and synthesized by substituting selected heteroatoms of high-performance TADF materials with heavy-atom selenium. A new series of multicolor TADF materials with remarkable EQEs are achieved. One of these materials, SeDF-B, results in pure blue emission with EQEs approaching 20%. Additionally, flexible graphene-based electrodes are developed for OLEDs and revealed to have similar performance as standard indium tin oxide (ITO) in most cases. These devices are the first report of TADF based OLEDs that utilize graphene-based anodes.