showed significant efficiency roll-off, with EQE1000 of 12.4, 11.4, and 11.7%, respectively. The device performance was significantly improved with the addition of CTPCF3 as an assistant dopant in HF-OLEDs, which showed EQEmax of 30.5, 37.2 and 27.5%, respectively, while the EQE1000 remained high at 26.2, 34.3 and 24.1%, respectively. Using a very similar emitter design, Jiang et al. reported BN-CP1 and BN-CP2, two compounds featuring carbazoles positioned either at the ortho or meta positions of a pendant phenyl ring, which itself is substituted para to the boron atom of the MR-TADF core DtBuCzB (Figure ). BN-CP1, a carbazole analogue to D-Cz-BN, is more resistant to ACQ, evidenced by the almost unchanged FWHM of 25 to 26 nm upon increasing the doping concentration from 1 to 30 wt% in DMIC-TRZ film, while the FWHM broadens from 26 to 43 nm for BN-CP2 across the same range of doping concentrations. The device with BN-CP1 showed an unchanged electroluminescence (EL), lEL= 496 nm and FWHM = 25 nm, and a smaller decrease in the EQEmax from 40.0 to 33.3%, as the doping concentration increased from 5 to 30 wt%. By contrast, the device with BN-CP2 showed red-shifted and broadened EL (lEL from 494 to 502 nm and FWHM from 25 to 33 nm) and the EQEmax decreased to 23.7 from 36.7% across the same doping concentration range. These two studies reveal the value of judiciously placed bulky substituents to mitigate ACQ. Following a similar strategy, Xie et al. reported another analogue of D-Cz-BN that contains four tert-butyl carbazoles on the pendant phenyl ring of the same DtBuCzB MR-TADF core (6TBN, Figure ). 6TBN also exhibited strong resistance to aggregation, reflecting in its almost unchanged emission spectra (lPL ranging from 497-499 nm and FWHM ranging from 25-29 nm) in mCP films with doping concentrations ranging from 10 to 100 wt%. The 20 wt% in mCP and host-free SP-OLEDs with 6TBN showed an EQEmax of 23.0 and 12.3%, respectively. Luo et al. reported an encapsulated TADF emitter, NBNN2 (Figure ) that contains the BN2 MR-TADF core, which is flanked by N-centred and O-bridging donor (DPXZ) moieties, all linked via a common carbazole scaffold. This sandwich configuration endows NBNN2 a resistance to aggregation as the emission profile is almost unchanged (lPL ranging from 531 to 534 nm and FWHM ranging from 39 to 40 nm) as the doping concentration increasing from 10 to 50 wt% in mCP; however, there is a rather significant decrease in the FPL from 91 to 52%. Owing to the through space charge transfer (TSCT) excited states that form as a result of the interactions between BN2 and the flanking groups the reverse intersystem crossing rate constant (kRISC) was found to be high for MR-TADF emitters at 1.2×10 5 s -1 in 10 wt% doped films in mCP. The devices with NBNN2 showed high EQEmax of 31.7% and a small efficiency roll-off, with EQE1000 of 20.9% and EQE3000 of 16.7%.