Since the first report of an MR-TADF compound from the group of Hatakeyama, over two hundred separate MR-TADF materials have been identified as hosts or emitters for OLEDs, with examples of their use in high-efficiency blue, green and red OLEDs. Near UV and violet emitters for OLEDs are one class where there is a dearth of reports. Potential uses of short wavelength OLEDs are for sensing, photocopying, high density information storage and sterilization. Most of the reported efficient near UV OLEDs (<400 nm) using purely organic emitters to date contain materials that emit from a hybridized local and charge transfer excited state (HLCT) where triplets are harvested through a hot exciton channel mechanism involving reverse intersystem crossing (RISC) from higher lying triplet (Tn) states to S1. A recent report from Tang et al. demonstrated record setting performance values for an HLCT emitter-based near UV-OLED [λEL = 396 nm, EQEmax = 10.79%, CIE (0.161, 0.031)]. There are also a small number of reports of near UV TADF and MR-TADF emitters and their use in OLEDs (Figure ). The first report of a near UV-emitting MR-TADF compound is based on a boron, oxygen doped triangulene type structure reported by Hatakeyama, 2a (λPL = 398 nm, FWHM = 33 nm, ΔEST = 0.18 eV, τD = 66 μs in 1wt% PMMA). This compound, also known as DOBNA, was initially identified as a potential host material due to its large band gap and high triplet energy. In the same report, phenyl derivatives of 2a were employed as host materials in phosphorescent OLEDs. Other reports have mostly documented the use of the DOBNA fragment as a weak acceptor in D-A type violet (λPL < 450 nm) TADF emitters. In 2015, Kwon et al. reported two deep blue emitters containing the DOBNA fragment as the acceptor. The OLED with the acridine donor-based emitter, TDBA-Ac presented an EQEmax of 21.5% and an excellent CIEy of 0.06. Choi et al. reported devices using related tercarbazole donor-based TB-3Cz and TB-P3Cz emitters that showed EQEmax of 9.9% and 6.1%, respectively, with corresponding CIEy values were 0.07 and 0.08, respectively for TB-3Cz and TB-P3Cz. A structurally related deep blue emitter containing a spiroacridan donor was reported by Kim et al., TDBA-SAF-based device achieved an EQEmax of 28.2% and a CIEy of 0.09. Recently, Choi et al. reported two deep blue solution-processible emitters containing extended carbazole donor units connected to DOBNA acceptor, BO-tCzPhICz and BO-tCzDICz. The solution-processed OLEDs showed EQEmax of 17.8% and 14.8%, respectively, and with CIEy of 0.07 and 0.062, respectively. Hong et al. reported two tri-spiral acridine donor based blue emitters, OBOtSAc and tBuOBOtSAc and their use in OLEDs. Both emitters showed efficient (ΦPL above 90%) deep blue emission at 452nm (FWHM = 50 nm) and 446 nm (FWHM = 48 nm), respectively for OBOtSAc and tBuOBOtSAc. Both devices achieved very high EQEmax of 31.2% and 28.2% with CIEy of 0.092 and 0.061, respectively. Tong et al. reported OLEDs using two deep blue emitters TDBA-PAS and TDBA-DPAC that can achieve EQEmax of 22.4% and 24.6% at CIEy of 0.042 and 0.085, respectively. These two emitters each show two different conformers in the solid state and the authors contend that one conformer acts as a host for the other, evidenced by the improved performance in the device at high doping concentrations (≤ 50 wt%). Su et al. reported a disk-like emitter based on a DOBNA acceptor decorated with three diphenylamine units, BO3N, which showed narrowband blue emission (λPL = 424 nm, FWHM = 34 nm) with high ΦPL of 80% in toluene solution. The OLED with the emitter BO3N showed an EQEmax of 10.4% and CIEy value of 0.08. The DOBNA fragment has thus been shown to be a promising motif used in the construction of D-A type efficient deep blue TADF emitters. An alternative design for UV emitters was highlighted by Lee et al. where they reported a fused indolocarbazole (tDIDCz) derivative that presented incredibly narrowband EL (FWHM = 14 nm, λEL = 401 nm) with CIE coordinates of (0.164, 0.018) in the device. Though this compound shows the characteristic pattern of alternating increasing and decreasing electron density on adjacent atoms in the excited state, the DEST of 0.44 eV is too large due to the very different natures of the S1 and T1 excited states resulting in the absence of delayed fluorescence. The absence of triplet harvesting in the OLED limited the EQEmax to only 2.75% (Table ). In 2020, we reported a near UV emitting linear ladder type B,N-doped heptacene (Figure ), α-3BNOH (λPL = 390 nm, FWHM = 31 nm, ΔEST = 0.31 eV in THF) that showed an emission resulting from TADF and TTA and narrow deep blue emission in solution. By replacing the OH group attached to boron with mesityl units in α-3BNOH, a red shift of the emission was observed for α-3BNMes (λPL = 443 nm, FWHM = 30 nm, THF, ΔEST = 0.28 eV, 1 wt% in PMMA). Here, we report two emitters, one based on an A-D-A design containing two DOBNA acceptor groups that emits in the deep blue (DIDOBNA-N), and a second B,N,O doped heptacene MR-TADF compound that emits in the near UV (MesB-DIDOBNA-N). Both compounds exhibit weak TADF due to their moderately large DEST of 0.23 and 0.24 eV yet demonstrate high FPL of 81 and 75% for DIDOBNA-N and MesB-DIDOBNA-N, respectively. The OLED with DIDOBNA-N showed deep blue emission at 444 nm (FWHM = 64 nm) corresponding to CIE coordinates of (0.152, 0.073) with an EQEmax of 15.2%. The OLED with MesB-DIDOBNA-N showed near UV emission with lEL of 401 nm, FWHM = 22 nm, corresponding to CIE coordinates of (0.165, 0.044). By increasing the doping concentration of MesB-DIDOBNA-N in the emitting layer of the device, from 1.5 wt% to 3 wt% and 5 wt%, the EQEmax increased from 9.3%, 11.3% and 13.6% respectively. Only minor variances were observed in the emission maxima and CIEy value with increasing doping concentration. The EQEmax value of the 5 wt% doped device represents the most efficient device among those employing purely organic violet emitters.