Narrowband Emission from Organic Fluorescent Emitters with Dominant Low‐Frequency Vibronic Coupling

Abstract

Organic fluorescent emitters with narrowband emissions are highly desirable for high‐resolution organic light‐emitting diode (OLED) display technology. In principle, this can be achieved by specifically controlling the intrinsic structural relaxation and vibronic coupling in the excited state. Here, a design strategy to realize narrowband emission of organic fluorescent emitters is proposed by significantly enhancing the low‐frequency vibronic coupling strength (Λ) while simultaneously reducing the high‐frequency Λ of the commonly involved stretching modes. The quinolino‐[3,2,1‐de]acridine‐5,9‐dione (QAO) species is found to be directly associated with this design principle. By introducing single bond‐linked peripheral moieties into the QAO core, the constructed QAO derivatives are shown to exhibit better performance, by achieving a full width at half‐maximum of 23 nm/0.13 eV in toluene for the narrowest band as well as 27 nm/0.15 eV in doped devices, with negligible dependence on the doping concentrations. The maximum external quantum efficiency of the fabricated blue OLED is 17.5%.

Highly Efficient Electroluminescent Materials with High Color Purity Based on Strong Acceptor Attachment onto B–N-Containing Multiple Resonance Frameworks

“…in the emission spectrum owing to the involvement of vibrational progression separated by the vibrational frequency. 30 Based on the above analysis, it can be concluded that lowering the reorganization energies of the excitation and emission processes can be achieved by restricting the structural deformation between the ground and excited states, which may impart small Stokes shift and narrowband emission to TADF molecules eventually. S11 and Table S1), which are well consistent with the theoretically calculated results (Table S2).…”

“…Generally, the enhanced low-frequency and suppressed high-frequency vibronic coupling are conducive to narrow FWHM. [30][31][32] For DtCzB-DPTRZ, the representative normal vibration modes with large contribution to reorganization energies are nearly distributed in all-frequency regions. However, the observed reorganization energies for the different normal vibration modes of DtCzB-DPTRZ have extremely small values (< 20 cm −1 ).…”

Quenching‐Resistant Multiresonance TADF Emitter Realizes 40% External Quantum Efficiency in Narrowband Electroluminescence at High Doping Level

“…In this regard, the deplanarized/ sterically hindered MR-TADF skeleton should be designed with caution to reduce vibrational progression and retain high color purity. [17] Herein, we demonstrate a novel strategy to realize MR-TADF motif with concurrent ultrahigh color purity, efficiency, and concentration-resistance by shielding the B/N based chromophore with carbazolyl units. The target emitter BN-CP1 is derived by covalent linking the blueish-green BN-Cz skeleton with 1,3-di(9H-carbazol-9-yl)benzene (mCP), and an isomeric emitter BN-CP2 with flattened geometry is also constructed for comparison (Scheme 1).…”

Multi-resonant thermally activated delayed fluorescence emitters based on tetracoordinate boron-containing PAHs: colour tuning based on the nature of chelates

“…18 Large structural changes between the ground and excited states are responsible for the broad emission. 41 We exclude excimer or aggregate emission as the origin of the broad emission as the emission remains broad in dilute solution. We also note that the orthogonal arrangement of the phenyl substituent on the boron centre should effectively inhibit excimer or aggregate formation (see Fig.…”