Highly Efficient Solution-Processed Deep Blue Organic Light-Emitting Diodes with an External Quantum Efficiency of 17.2% Alleviate the Hole Accumulation with a Modifying Layer Prepared by the Spontaneous Spreading Method

Preparing multilayer organic films via a solution process without solvent intercalation is crucial for developing high-performance organic light-emitting diodes (OLEDs). This work elucidates a simple solution preparation method for efficiently stacking multilayer blue OLEDs. The process involves stamping different polymer films formed via spontaneous spreading (SS) on the water surface. These films can be stamped onto the blue emission layer without any interference from adjacent films as the modifying layer. Hence, high-performance blue OLEDs based on mCP:TDBA-AC with the emission peak at 465 nm have been fabricated on glasses and flexible substrates, in which the modifying layer with a mixture of poly[2-methoxy-5-(2-ethylhexyloxy) phenylenevinylene-1,4-diyl] and 1,3,5-Tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene was inserted via the SS method to alleviate the effect of leakage holes from the emission layer. By adjusting the mixing ratio of organic substances in SS films, the properties of the films can be effectively regulated to optimize the performance of blue OLEDs. Finally, highly efficient blue OLEDs with Commission Internationale de I'Eclairage coordinates of (0.15,0.15) and an external quantum efficiency (EQE) of 17.2% were prepared on glass substrates. In addition, an EQE of 15.6% was also achieved on a flexible substrate.