Circularly polarized luminescent-active small organic molecules with thermally activated delayed fluorescence properties

Abstract

Circularly polarized luminescent (CPL) materials have attracted considerable research interest, owing to their promising applications in three-dimensional displays, optical data storage and processing, asymmetric photosynthesis, etc. Thermally activated delayed fluorescence (TADF) materials possess the ability to harvest both singlet and triplet excitons, thereby achieving a theoretical internal quantum efficiency (IQE) of 100%. Benefiting from advantages such as an exact molecular structure, high luminescence efficiency, facile structural modification, tunable emission wavelengths and easy manufacturing processes, precious metal-free circularly polarized thermally activated delayed fluorescence small organic molecules (CP-TADF SOMs) have emerged as promising candidates for fabricating circularly polarized organic light-emitting diodes (CP-OLEDs). However, owing to the trade-off between the fluorescence quantum efficiency (Φ_F) and the luminescence dissymmetry factor (g_lum), the development of high-performance CP-TADF SOMs remains a critical challenge. This review highlights the recent research progress in this class of materials. It provides an overview of the design concepts, photophysical properties, chiroptical properties, and device performance for four categories of CP-TADF SOMs based on central, axial, planar, and helical chirality. Furthermore, the current challenges and future prospects are also discussed, with the aim of offering valuable insights for the design of high-performance CP-TADF materials.