High‐Performance Orange–Red Organic Light‐Emitting Diodes with External Quantum Efficiencies Reaching 33.5% based on Carbonyl‐Containing Delayed Fluorescence Molecules

Abstract

Developing orange to red purely organic luminescent materials having external quantum efficiencies (ηexts) exceeding 30% is challenging because it generally requires strong intramolecular charge transfer, efficient reverse intersystem crossing (RISC), high photoluminescence quantum yield (ΦPL), and large optical outcoupling efficiency (Φout) simultaneously. Herein, by introducing benzoyl to dibenzo[a,c]phenazine acceptor, a stronger electron acceptor, dibenzo[a,c]phenazin‐11‐yl(phenyl)methanone, is created and employed for constructing orange–red delayed fluorescence molecules with various acridine‐based electron donors. The incorporation of benzoyl leads to red‐shifted photoluminescence with accelerated RISC, reduced delayed lifetimes, and increased ΦPLs, and the adoption of spiro‐structured acridine donors promotes horizontal dipole orientation and thus renders high Φouts. Consequently, the state‐of‐the‐art orange–red organic light‐emitting diodes are achieved, providing record‐high electroluminescence (EL) efficiencies of 33.5%, 95.3 cd A−1, and 93.5 lm W‒1. By referring the control molecule without benzoyl, it is demonstrated that the presence of benzoyl can exert significant positive effect over improving delayed fluorescence and enhancing EL efficiencies, which can be a feasible design for robust organic luminescent materials.

Donor–Acceptor Type of Fused-Ring Thermally Activated Delayed Fluorescence Compounds Constructed through an Oxygen-Containing Six-Membered Ring

“…These EQE max values are significantly higher than the theoretical limit (ca. 5−7.5%) of the OLEDs based on traditional fluorophores, 1,16 confirming the contribution of TADF to electroluminescence. The 5 wt % doped device of t-BMA(OO)Q showed weaker EQE roll-offs at higher luminance compared with the corresponding device of PA(OO)Q (Figure 5), which is rational considering the shorter τ DF of the doped emitting layer of the t-BMA(OO)Q device.…”

“…49,52 The SOC matrix elements between the S 1 and T 1 /T 2 states of these compounds are small, suggesting weak SOC effects. 1 In the optimized S 1 -state geometries of these compounds, a nearly planar core skeleton is maintained, which indicates weak excited-state structural relaxations owing to the higher skeleton rigidity (Figure S2).…”

“…Purification of the residue by silica-gel column chromatography (petroleum ether/ethyl acetate = 4:1) provided compound 1 as a white solid (2.5 g, 23%). 1 This compound was synthesized according to the procedure of compound 1. The molar quantities of reactants were the same as those in the synthesis of compound 1.…”

Alkyl-Engineered Dual-State Luminogens with Pronounced Odd–Even Effects: Quantum Yields with up to 48% Difference and Crystallochromy with up to 22 nm Difference

“…On the other side, the development of OLMs has enabled wide applications in sensors, bioimaging, electronics, and smart devices. − Among the OLMs, dual-state luminogens (DSEgens) have been of particular interest in recent years as these materials can luminesce in both dilute solutions and the solid state . It is understood that conventional aggregation-caused quenching luminogens which only luminesce in dilute solutions or the trending aggregation-induced emission luminogens which only luminesce in the aggregated state are usually employed in their respective emissive state, namely, dilute solutions or aggregates. − In contrast, DSEgens are demonstrated to be applicable in both a molecularly dispersed state and an aggregated/solid state attributed to their DSE features. , It is clear that the emission intensity is a crucial property of a DSEgen.…”

A polymer acceptor containing a B ← N unit with strong fluorescence for organic photovoltaics

“…Organic light-emitting diodes (OLEDs) have been successfully commercialized and play an irreplaceable role in our daily life with the development of new emissive materials. [35][36][37][38] A lot of highly fluorescent conjugated polymers have already been developed because of their applications in OLEDs. 39,40 However, OSC device applications of these fluorescent conjugated polymers are rarely reported.…”