Hydrophobic small-molecule emissive layers enabling fully solution-processed high-performance OLEDs

The fabrication of OLEDs via fully solution-based techniques is a coveted advancement for large-area, high-luminance, and cost-effective organic light panels. A major challenge lies in preventing film dissolution or intermixing during multilayer deposition, especially when applying the electron transport layer (ETL) onto the emitting layer (EML). This study explores the use of hydrophobic host : guest small-molecule systems in the EML, which are typically considered too fragile for successive solution processing. We demonstrate that an ETL can be deposited from a hydroalcoholic solution without damaging the EML, thanks to the hydrophobic nature of the materials used. OLEDs were fabricated using both spin-coated and thermally evaporated ETLs to evaluate the performance. The best devices showed comparable results, reaching current efficiencies of ∼35 cd/A at 1000 cd/m 2 , with limited efficiency roll-off at higher luminance. Importantly, FTIR analysis confirmed that residual water from the ETL solution is eliminated during annealing. Lifetime measurements under ambient conditions confirmed the robustness of the devices, with lifetimes of approximately 150 hours from an initial luminance of 1000 cd/m 2 . These results provide new insight into the potential of commercial small-molecules for high-performance, multilayer OLEDs fabricated entirely through solution-processing methods.