Systematic strategy for high-performance small molecular hybrid white OLED via blade coating at ambient condition

Large-area organic light-emitting diodes (OLEDs) fabricated by solution process with low-cost are essential for practical applications. However, maintaining desirable uniformity and smoothness of prepared films are challenging with the enhancement of film size and layers. Reported herein is a systematic strategy of solvent and device structure engineering for designing small molecular hybrid white OLED (WOLED) via blade-coating. Benefiting from the uniform blade-coated films with low roughness about 1 nm as well as the balanced charge carrier transport, the blade-coated WOLED with hybrid fluorescence and phosphorescence (small area 0.1 cm2) shows the maximum current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE) of 29.0 cd A−1, 30.4 lm W−1, and 11.6%, respectively. And the WOLEDs achieve low turn-on voltage (Von) of about 2.8 V. Meanwhile, the all-vacuum-based WOLED reaches maximum CE, PE, and EQE of 40 cd A−1, 44.3 lm W−1, and 15.9%, respectively. Remarkably, a larger area of the device (2 cm × 2 cm) with uniform emitting reaches peak EQE of 6.8% by blade-coating, notably, only a small amount of solution about 0.9 μL/cm2 was consumed for blade-coated films. The high-performance and low-cost WOLED via blade-coating is ascribed to the facile strategy to improve the film morphology and the energy-level matching, which provides huge potential in display and flat panel lighting.