Unlocking Solution‐Processable Deep‐Blue “Hot‐Exciton” Electroluminescence via High‐Throughput Optimized Aqueous Organic Nanoparticles

ABSTRACT The “hot‐exciton” materials allow for the efficient harvesting of high‐lying triplet excitons, making them promising candidates for high‐performance blue organic light‐emitting diodes (OLEDs). However, the fabrication of solution‐processed deep‐blue OLEDs is limited by the toxicity of conventional organic solvents for emissive‐layer deposition. To overcome this issue, we present a high‐throughput strategy for developing blue OLEDs based on water‐dispersible organic nanoparticles (NPs). Based on systematic high‐throughput experimentation, we optimize the processing parameters for NP‐based films and elucidate their process–photophysics–device relationships. The optimized organic NP films processed from aqueous suspension exhibit improved low‐voltage operation and enhanced peak device efficiency compared to films cast from traditional organic solvents. The corresponding OLED devices achieve a maximum external quantum efficiency ( EQE MAX ) of 4.1%, deep‐blue emission with a peak at 448 nm, and a low turn‐on voltage of 3.8 V. Combined morphological and interfacial analyses suggest that the reduced turn‐on voltage arises from the coupled effects of altered interfacial energetics and deposition‐induced interfacial morphology. This work demonstrates a practical aqueous nanoparticle approach for emissive‐layer deposition in solution‐processed deep‐blue OLEDs.