(a) “One platform–three emitters” concept: Divergent one-pot borylation of a 5,11-dihydroindolo[3,2-b]carbazole-based precursor IDCz-Br affords three structurally distinct MR-TADF emitters (BN-G, BN-Y, and BN-R) in a single synthetic operation, enabling green-to-red narrowband emissions. (b) Molecular structures (front view of the (P) conformer) and crystal packing diagrams of BN-G (top), BN-Y (middle), and BN-R (bottom), determined by single-crystal x-ray diffraction, with thermal ellipsoids drawn at the 50% probability level; hydrogen atoms are omitted for clarity [52].#
DFT-calculated reaction pathways elucidating the divergent formation of the regioisomers BN-Y and BN-R on the basis of the relative Gibbs free energies (Δ_G_) of plausible intermediates. Calculations were performed at the M06-2X/def2-SVP(SMD = toluene)//def2-TZVP(SMD = toluene) level at the experimental reaction temperature (438 K). Kohn–Sham HOMO distributions and the corresponding energy levels (_E_HOMO) of representative intermediates are included.#
(a) UV–vis absorption and (b) PL spectra of BN-G, BN-Y, and BN-R in toluene (10−5 M). (c) Steady-state PL spectra and (d) transient PL decay profiles of 1 wt%-doped films in an mCBP host measured at 300 K under N2. Insets in (c) and (d) show photographs of the doped films exhibiting green-to-red emissions upon 365 nm UV irradiation, and the prompt fluorescence decay in the nanosecond regime, respectively.#
(a) Vibrationally resolved emission spectra for the S1 → S0 transition of BN-G (top), BN-Y (middle), and BN-R (bottom), calculated at the B3LYP/6-31G(d) level. Stick spectra (black lines) are convoluted with Gaussian functions to generate the emission profiles. (b) Huang–Rhys factor (_S_i) distributions as a function of vibrational frequency (
mathematical equation
), illustrating the mode-resolved vibronic coupling. Insets show the high-frequency region (
mathematical equation
= 1250–1750 cm−1). (c) Representative vibrational modes, including the dominant low-frequency scissoring mode (Mode 1) and selected high-frequency stretching modes contributing significantly to the vibronic progression.#
最后，研究人员评估了三种发光材料在OLED器件中的电致发光性能。如图5所示，以双极性DMIC-Trz作为主体材料构建的掺杂器件表现出出色的发光效率与色纯度，BN-G、BN-Y与BN-R的电致发光峰值分别为519 nm、541 nm和600 nm，半峰全宽维持在24至25 nm。器件的最大外量子效率分别达到了27.2%、31.1%和30.3%（在mCBP主体器件中，BN-Y的最大外量子效率更是高达35.3%）。其中，BN-G的色坐标为(0.22, 0.72)，高度贴近超高清显示的Rec.2020绿光标准。得益于高效的载流子注入与平衡，DMIC-Trz主体器件的启动电压低至2.6 V，在1000 cd m⁻²的初始亮度下，器件的半衰期寿命达到了1100至2500小时，展现出极佳的运行稳定性。
(a) Energy-level diagram and chemical structures of the materials used in TADF-OLEDs based on BN-G, BN-Y, and BN-R with the DMIC-Trz host (Film B). (b) EL coordinates in the CIE chromaticity diagram. (c) EL spectra recorded at 1000 cd m−2. (d) Current density–voltage–luminance (J–V–L) characteristics. (e) External quantum efficiency–luminance (EQE–L) plots. (f) Operational stability, represented by the temporal evolution of EL intensity at an initial luminance (_L_0) of 1000 cd m−2.#
