Circularly Polarized Electroluminescence of Thermally Activated Delayed Fluorescence-Active Chiral Binaphthyl-Based Luminogens

Abstract

Two pairs of thermally activated delayed fluorescence (TADF)active chiral luminogens (R/S-1 and R/S-2) can be achieved by introducing D− A-type groups to chiral BINOL skeletons. The resulting chiral luminogens can exhibit aggregation-induced emission properties in THF−water mixtures and TADF emission in a doped-film state. The absolute photoluminescence quantum yield (Φ PL ) and delayed fluorescence lifetimes (τ delayed ) were measured to be 18.5% and 1.03 μs for R-1 and 15.7% and 0.97 μs for R-2. However, only R/S-1 with the fixed conjugation structure can emit circularly polarized luminescence signals, and g lum can reach 1.6 × 10 −3 in toluene solution and 9.2 × 10 −4 in the neat film. Most importantly, R/S-1 was chosen as the emitting layers for orangered circularly polarized organic light-emitting diodes, which can display low turnon voltage (V on ) of 3.4 V, high maximum brightness (L max ) up to 40 470 cd m −2 , moderate external quantum efficiency of 4.1%, as well as circularly polarized electroluminescence signal with g EL = −0.9 × 10 −3 /+1.0 × 10 −3 .

Circularly Polarized Luminescence of a Stereogenic Curved Paraphenylene Anchoring a Chiral Binaphthyl in Solution and Solid State

“…[10][11][12][13][14][15][16][17][18] The g CPL value is defined as 2(I L ÀI R )/(I L + I R ), where I L and I R denote left-and right-handed CPL intensity, respectively.I np articular, fora pplications such as circularly polarized organic light emitting diodes( CP-OLEDs), am aterial should exhibit its CPL properties in the solid state. [19][20][21][22][23] However,t he precise relationship between the CPL properties and molecular structure in the solid and solution state remains un-clear,a nd hence the development of reasonable molecular designl eading to an effective CPL dye is still an ongoing critical issue. [24] Cyclic curved p-conjugated systems, such as cycloparaphenylene( CPP) [25][26][27] and carbon nanobelts [28,29] amongo thers,a re of considerable interest owing to their attractive molecular structures, unique photophysical applications.W hen cyclic punits are connected inahelical arrangement along the axial direction, the resulting p-conjugated system exhibits chirality.…”

Solution‐Processed White Circularly Polarized Organic Light‐Emitting Diodes Based on Chiral Binaphthyl Emitters

“…In this study, a pair of sky‐blue chiral D‐A type emitters ( S ‐/ R ‐ BN‐tCz ) containing chiral 1,1’‐binaphthol, benzophenone acceptors and carbazole donors were successfully synthesized (Figure 1). Orange S ‐/ R ‐ BN‐PXZ emitters were also synthesized according to our previous work [17] . Notably, S ‐/ R ‐ BN‐tCz showed good film‐forming property, thermal stability as well as high fluorescence quantum yields, and their non‐doped blue CP‐OLEDs could display high brightness and intense CP‐EL signals.…”

“…As is evident from Figure 4 b, S ‐/ R ‐ BN‐tCz enantiomers could emit obvious mirror‐image CPL signals centered at 486 nm with the luminescence dissymmetry factors ( g lum ) values of +2.68 × 10 −3 / − 2.74 × 10 −3 in spin‐coated films, which was favored for constructing CP‐OLEDs emitting intense CP‐EL. The circularly polarized photoluminescence (CPPL) properties of S ‐/ R ‐ BN‐PXZ have been fully studied in our previous work [17] …”

Maximizing Chiral Perturbation on Thermally Activated Delayed Fluorescence Emitters and Elaboration of the First Top‐Emission Circularly Polarized OLED

“…[8] With BINOL derivatives as the acceptor, Cheng and workers have constructed CP-TADF molecules exhibiting g lum values of up to 1.6 × 10 −3 . [9] Another innovative molecular design involving two TADF chromophores templated by a chiral 1,2-diaminocyclohexane unit was subsequently developed by Chen and coworkers. [10] Thereafter, other intrinsically chiral TADF chromophores were reported.…”