[2.2]Paracyclophane‐Substituted Chiral Multiresonant Thermally Activated Delayed Fluorescence Emitters for Efficient Organic Light‐Emitting Diodes

Abstract

AbstractThe study reports two pairs of chiral multi‐resonant thermally activated delayed fluorescence (MR‐TADF) materials PCP‐DiKTa and Czp‐DiKTa by decorating a known MR‐TADF core, DiKTa, with different [2.2]paracyclophane (PCP) based planar chiral groups. PCP‐DiKTa shows narrow sky‐blue emission with a full width at half maximum (FWHM) of 44 nm, while the emission of Czp‐DiKTa is slightly broader with a FWHM of 66 nm and redshifted. Both emitters show high photoluminescence quantum yields of 93 and 99% for PCP‐DiKTa and Czp‐DiKTa, respectively. Enantiomerically pure samples of both compounds show chiroptical properties in the ground state while only Czp‐DiKTa exhibits chiroptical activity in the excited state, with dissymmetry factors (|gPL|) of 4 × 10−4. Organic light‐emitting diodes (OLEDs) with PCP‐DiKTa and Czp‐DiKTa show maximum external quantum efficiencies (EQEmax) of 25.7 and 29.2%, with λEL of 489 and 518 nm, and FWHMs of 53 and 69 nm, respectively. These EQEmax values are higher than those of other reported devices employing PCP‐based D‐A type emitters. This work demonstrates that the PCP moiety is not only a powerful building block to develop planar chiral emitters but one that is compatible with the fabrication of high efficiency devices.