Designs and Applications of Circularly Polarized Thermally Activated Delayed Fluorescence Molecules

Abstract

The design of fluorophores merging circularly polarized luminescence and thermally activated delayed fluorescence properties has recently emerged as a promising direction for the development of efficient CP‐Organic Light‐Emitting Diodes (CP‐OLEDs). This progress report gives an overview of the molecular designs explored to obtain CP‐TADF properties, of their performances as chiral emitters in CP‐OLEDs, and discusses future challenges for this burgeoning field of research.

Pathways to increase the dissymmetry in the interaction of chiral light and chiral molecules

“… 108,109 While efforts have been taken to make chiral versions of such small molecules, in almost all cases | g lum | is impractically low (<10 −2 ). 110 In contrast, polymeric thin film systems can allow for the generation of CP-OLEDs with | g lum | >1. Furthermore, by focusing on polymeric systems that exhibit high intrinsic chiroptical activity, rather than structural chirality, it is possible to maintain the optimum thin film thickness (∼100 nm) required for high performance devices.…”

High‐Efficiency Circularly Polarized Electroluminescence from TADF‐Sensitized Fluorescent Enantiomers

“…Moreover, the PLQY of ( S , S )‐ CPAD was recorded to be 0.98 in un‐degassed toluene, and the PL transient decay curve of the enantiomer was also recorded in toluene with fluorescence lifetime of 12.47 ns (Figure S11). Thus, the κ r of ( S , S )‐ CPAD was calculated to be 7.8×10 7 s −1 with the equation of k r = ϕ PL / τ , which is higher than all of the reported CP‐TADF emitters [1c] …”

“…Meaningfully, the TADF‐sensitized fluorescent devices show high EQE max of 21.5 % and remarkably low efficiency roll‐off, whose EQEs are 21.2 % and 15.3 % at 1000 and 10 000 cd m −2 , respectively. Moreover, the obtained EQEs of TADF‐sensitized CP‐FL emitters are comparable to those of CP‐TADF emitters, [1c] which provides a promising perspective to not only break through the EL efficiency limit of CP‐FL emitters, but also expand the kinds of efficient CPEL materials.…”

“…Intriguingly, the efficiencies of this TADF‐sensitized devices were much higher than that of reported CP‐OLEDs based on CP‐FL emitters (EQE max <5 %) (Table S11), and they were also higher than that of most devices based on CP‐TADF emitters (see Table S12). Importantly, the device exhibited extremely low efficiency roll‐off, whose EQEs were 21.2 % and 15.3 % at 1000 and 10 000 cd m −2 , respectively, which was the best of all the reported CP‐OLEDs (see Table S11,S12) [1c, 5] …”

Chiral Thermally Activated Delayed Fluorescence Materials Based on R/S‐N2,N2′‐Diphenyl‐[1,1′‐binaphthalene]‐2,2′‐diamine Donor with Narrow Emission Spectra for Highly Efficient Circularly Polarized Electroluminescence

“…[ 3 ] Particularly, circularly polarized TADF (CP‐TADF) materials not only possess TADF properties but could also emit left‐ and right‐handed CP light ( I L and I R ) with different intensities, arousing extensive concern in fabricating circularly polarized OLEDs (CP‐OLEDs). [ 4 ] Owing to directly generating circularly polarized electroluminescence (CPEL), CP‐OLEDs could avoid power loss and complicated device structures compared with the conventional methods of obtaining CP light. [ 5 ] However, in terms of the current research, the most common ways to construct CP‐TADF materials are through chiral perturbation strategy by introducing chiral units, such as 1,2‐diaminocyclohexane, [ 6 ] chiral binaphthol (BINOL), and its derivatives, [ 7,8 ] into the twisted D‐A structures.…”