Closing the Gap: Multiresonant TADF Emitters and TADF Dendrimers in Solution-Processed OLEDs

Conspectus Organic light-emitting diodes (OLEDs) have become a cornerstone technology in modern displays, yet their dominant manufacturing route, vacuum deposition (VD), remains cost-intensive and intrinsically wasteful. Solution processing (SP) offers an attractive alternative because it enables high-throughput fabrication, reduced material loss, and compatibility with large-area and flexible substrates. Organic thermally activated delayed fluorescence (TADF) emitters are uniquely positioned for SP-OLEDs, as they can harvest both singlet and triplet excitons, providing a route to near-unity device internal quantum efficiency, without the need for scarce heavy metals. The key challenge, however, is that the performance of SP TADF OLEDs still lags behind VD devices in both maximum external quantum efficiency and efficiency roll-off. These performance gaps originate from SP-specific constraints such as unoptimized film morphology, aggregation-caused quenching (ACQ), limited control over transition dipole orientation, and charge imbalance in multilayer stacks. Consequently, closing the VD–SP performance divide requires coordinated progress in molecular engineering and device engineering. This Account summarizes recent materials-design strategies for high-performance SP TADF OLEDs, with emphasis on multiresonant TADF (MR-TADF) emitters and TADF dendrimers. Small-molecule donor–acceptor (D-A) TADF emitters, though compatible for SP-OLEDs, often show broad emission resulting from their emissive long-range charge-transfer (LRCT) states and large reorganization energies, compromising color purity. MR-TADF emitters address this limitation, providing narrowband emission from a short-range charge-transfer (SRCT) state resulting from the alternating HOMO/LUMO density on adjacent atoms. Yet even state-of-the-art MR-TADF materials that deliver outstanding VD-OLED performance yield SP-OLEDs showing a marked drop in performance, evidencing that processing-induced disorder and bimolecular quenching become dominant in these devices. We therefore highlight how contemporary MR-TADF emitter design has shifted beyond solubility improvements toward deliberate control of film-state organization (e.g., liquid-crystalline self-assembly to induce preferential horizontal dipole orientation and improve outcoupling) and excited-state kinetics (e.g., multichromophore coupling and intramolecular FRET concepts to accelerate effective triplet harvesting and reduce roll-off while retaining narrow emission). In parallel, TADF dendrimers combine the high solubility and film-forming ability of polymers with the high purities possible with small molecules. This leads to SP devices showing comparable performance to VD ones. We discuss how dendrimer design has progressed from early low-performing prototype devices to SP-OLEDs showing EQEmax approaching 30%. We discuss how dendrimer design provides additional levers to modulate charge balance and efficiency roll-off. Importantly, dendrimers have also proven to be versatile beyond OLEDs, for example, in scalable bar-coated light-emitting electrochemical cells and in sensing, illustrating their broader relevance within organic electronics. Finally, we show that MR-TADF dendrimers, particularly when combined with hyperfluorescence (HF) device concepts, can integrate narrowband emission, high photoluminescence efficiency, aggregation suppression, and improved exciton management, enabling SP-OLED performances approaching VD benchmarks. Many bottlenecks of SP-OLEDs, ACQ, limited orientation control, and slow MR-TADF RISC have now been addressed individually. The next step is to integrate these insights into unified emitter host device design rules. MR-TADF emitters and dendritic architectures, especially in HF concepts, provide a promising pathway toward truly scalable, high color-purity OLED manufacturing.