To reveal the geometrical stability of both emitters, we calculated the energy barriers (ΔG ‡ ) associated with the racemization process. As illustrated in Figure , high ΔG ‡ s of 45.74 kcal/mol and 42.05 kcal/mol were obtained for BN[8]H-ICz and BN[8]H-BO, respectively. It is commonly believed that for a stable helicene, a minimum threshold of ΔG ‡ = 24 kcal/mol should be realized. The much higher ΔG ‡ s manifested the good geometrical chiral stability of both emitters, highlighting the contribution of helical extension and a rigid skeleton to the increased racemization energy barrier. [nm] were characterized using CD and CPL spectra in toluene (1.0ⅹ10 -5 M). The enantiomers displayed mirror-image CD spectra with opposite Cotton effects, and the anisotropy factors (gabs, defined as Δɛ/ɛ) were quantified as +4.83/-4.65ⅹ10 -4 at 415 nm and +3.01/-2.97ⅹ10 -3 at 520 nm (Figure ). The absolute configurations have been simulated by the computed ECD value, supporting the assignment of the first fraction to M-BN[8]H-ICz and the second to P-BN[8]H-ICz isomer, consistent with BN[8]H-BO (Figure ). CPL spectra were characterized in both solution and solid states, with the glum calculated to be +2.41/-2.37ⅹ10 -4 at 525 nm for P/M-BN[8]H-ICz, and +2.75/-2.52ⅹ10 -3 at 550 nm for P/M-BN[8]H-BO in toluene. In the doped film state, glum values were +2.27/-2.21ⅹ10 -4 at 530 nm for P/M-BN[8]H-ICz, and +2.15/-2.10 ⅹ10 -3 at 560 nm for P/M-BN[8]H-BO. The BCPL values were calculated to be 1.2 and 13.7 M -1 cm -1 respectively according to the recent definition (BCPL=ɛⅹΦPLQY ⅹ glum/2) . Overall, BN[8]H-ICz and BN[8]H-BO showed similar properties regarding their helical structure, stacking mode, and photophysics. However, the glum values of BN[8]H-BO were nearly an order of magnitude larger than those of BN[8]H-ICz, confirming our conclusion that the chiral properties of the molecules are predominantly governed by the electronic structure helicene properties. phenylpyridin-3-yl)anthracene, 30 nm)/ LiF (0.7 nm)/ Al (100 nm). In this device architecture, HATCN and LiF were used as hole and electron injection layers; TAPC and DPPyA served as hole and electron transport layers; TCTA/CzPhPy were chosen as electron-and hole-blocking layers. The EML contained an optimized ternary system with a DMIC-TRZ host, 10 wt.% phosphor assistant Ir(ppy)3, and 1.0 wt.% dopant (Figure ). showed a higher gCPEL than glum. We believe that the reason should be attributed to the lightorbital coupling from the geometrical helicene structures. As pointed out by Zheng et al in a recent work, chiral material could also work like an organic polarizer in the devices to polarize the light from the luminescence layer. In our device, the above emitters in the emitting layers would act as organic polarizers for the below emitters, which thus leads to a larger gCPEL. EL peak wavelength. b) Turn-on voltage (Von). c) Maximum luminescence (L). Full-width at half-maximum of the EL spectrum given in wavelength and energy. e) Maximum external quantum efficiency (EQE), value at 100 and 1000 cd/cm 2 . f) CIE coordinates at 1000 cd/cm 2 . The operational lifetimes at an initial luminance of 2000 cd/cm 2 . Furthermore, the operation stability of those devices was also testified under a constant current density at an initial luminance of 2000 cd/m 2 . Excitingly, both emitters demonstrated remarkable stability, with ultra-long lifetimes LT95 (time to 95% of the initial luminance) of approximately 401 hours for P- BN[8]H-ICz and 225 hours for P-BN[8]H-BO. The LT95 at an initial luminance of 1000 cd/m 2 can be extrapolated using an equation of LT95 (1000 cd/m 2 ) = LT95 (2000 cd/m 2 ) ⅹ(2000 cd/m 2 / 1000 cd/m 2 ) n with a regular degradation acceleration factor (n) of 1.7, being 1302 h and 731 h, respectively. To the best of our knowledge, although various chiral emitters for CP-OLED devices have been extensively reported, there has been limited exploration into device stability, which is a critical factor hindering the commercialization of CP-OLED technology. Our work here firstly studied the operation stability of green CP-OLEDs and state-of-the-art stability was obtained compared with the device using non-CPL emitters.