In view of the outstanding EL performance of CCO-2, it is chosen as an example for the fabrication of deepblue and green HF OLEDs with the configuration of ITO/HATCN (5 nm)/TAPC (50 nm)/TCTA (5 nm)/mCP (5 nm)/EML (20 nm)/DPEPO (5 nm)/TmPyPB (30 nm)/LiF (1 nm)/Al. In EML, the commercially available deep-blue and green MR-TADF materials of DABNA-NP-TB and BN2 45 are adopted as dopants, whose absorption spectra are partially overlapped with the PL spectrum of CCO-2 (Supplementary Fig. ). And CCO-2 doped in 9-(3-(9H-carbazol-9-yl)phenyl)-9H-3,9'-bicarbazole (mCPBC) and 2,6-bis(4-(9Hcarbazol-9-yl)phenyl)pyridine (2,6-DCzPPy) hosts with a doping concentration of 40 wt% functions as the sensitizer for DABNA-NP-TB and BN2 (doping concentration = 1 wt%), respectively. The HF OLED based on DABNA-NP-TB radiates high-purity deep-blue light with an EL peak at 456 nm (CIEx,y = 0.14, 0.10; FWHM = 31 nm) and a maximum luminance reaching up to 21670 cd m -2 . Meanwhile, a remarkable ηext of 32.5% is attained, verifying this device is one of the best HF OLEDs with EL peaks < 460 nm . The HF OLED based on BN2 shows strong green light with an EL peak at 540 nm (CIEx,y = 0.32, 0.64; FWHM = 41 nm) and a maximum luminance as high as 33930 cd m -2 . Impressive ηC, ηP and ηext of 158.8 cd A -1 , 136.8 lm W -1 and 37.6% are achieved, being the highest EL efficiencies for green MR-TADF materials . The operational lifetimes of these HF OLEDs are also investigated. Two kinds of device structures are optimized for DABNA-NP-TB (HF1 and HF2, device structures are listed in Supplementary Materials). Devices HF1 and HF2 display deep blue lights with CIEx,y of (0.14, 0.12) and (0.14, 0.10) and provide maximum ηexts of 23.5% and 17.0%, respectively (Supplementary Fig. and Table ). The operational lifetimes (LT50) for the luminance to decay to 50% of the initial luminance of 1000 cd m -2 are 9.8 and 21.9 h for HF1 and HF2, respectively, and the estimated LT50 values at 100 cd m -2 initial luminance are calculated as 621 and 1099 h, respectively, with a decay factor of 1.7. It is worth noting that, at 100 cd m -2 initial luminance, the LT80 values of HF1 and HF2 are 133 and 250 h, respectively, significantly advanced relative to the reported data (ηext = 19.5%; LT80 = 19 h) for DABNA-NP-TB . Device HF3, optimized for BN2, shows green light (CIEx,y = 0.33, 0.63) with a maximum ηext of 29.7%, and the LT50 at 1000 cd m -2 initial luminance is 692 h, from which the LT50 at 100 cd m -2 initial luminance is obtained as 34669 h. These operational lifetimes acquired in common laboratory are virtually good (Supplementary Table ), and could be further improved under better conditions with robust functional materials in industry.