Moreover, the fused MR segment enhances the SRCT property of BN[8]H-BO, a narrowband green emission peaking at 538 nm with an FWHM of merely 34 nm was observed, which is relatively narrower than most multiresonance CPL helicenes reported. The corresponding OLEDs showed not only high efficiency with EQEmax of 31.7% which remains 31.0% at 1000 cd/m 2 , but also large gCPELs of +5.23/-5.07ⅹ10 -3 . Noteworthy, an extremely long LT95 of 731 h at an initial luminance of 1000 cd/m 2 was obtained for the same device. Our research underscores that chiral helical emitters are among the most promising building blocks for achieving a combination of narrowband emission, high device efficiency, high color purity (CPEL), and high stability simultaneously. Our findings here are anticipated to accelerate the development of highly performed emitters with helical chirality.