Design and synthesis of chiral thermally activated delayed fluorescence emitters for organic light emitting diodes

Organic circularly polarized thermally activated delayed fluorescence (CP-TADF) emitters have received significant attention for use in organic light-emitting diodes (OLEDs) because they utilize both singlet and triplet excitons, achieving up to 100% theoretical internal quantum efficiency, and emit circularly polarized light. However, their broad emission from the large molecular relaxation leads to unsatisfied color purity. Multi-resonant TADF (MR-TADF) compounds address this by featuring separated frontier molecular orbitals, enabling a small energy splitting between the first singlet and triplet excited states (ΔE_{ST}), and a rigid structure, ensuring narrowband emission and high photoluminescence quantum yield. Circularly polarized OLEDs (CP-OLEDs) are promising for energy-efficient 3D and high-resolution displays. Developing emitters with narrowband emission, high efficiency, and high dissymmetry factor circularly polarized luminescence (CPL) remains a challenge. This thesis investigates the design of chiral TADF emitters having fast reverse intersystem crossing process, and CP-MR-TADF emitters that are capable of two-photon excited CPL. Chapter 1 introduces OLED mechanisms, and the principles of photoluminescence and electroluminescence. The design of TADF emitters, and an overview of the development of CP-MR-TADF emitters are also included. Chapters 2 and 3 introduce emitter designs that merge the planar chiral motif [2.2]paracyclophane (PCP) and known MR-TADF emitter DiKTa and tCzBN, respectively, aiming to explore the role that the PCP plays, including a through-space heavy atom effect on perturbing their photophysical and chiroptical properties, and their OLED performance. Chapter 4 presents a novel emitter combining tCzBN and DiKTa at the pseudo-ortho position of PCP to accelerate RISC, while maintaining both CPL and narrowband emission. Chapter 5 introduces a new emitter incorporating a novel carbazolophane (1,7)tBuCzp, and its photophysical, chiroptical performance, and OLED performance. Chapter 6 discusses the first reported two-photon excited CP-MR-TADF emitters, featuring excellent chiroptical properties and two-photon absorption cross-sections. Chapter 7 details the experimental methods used in this thesis.