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

Abstract

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 cm 2 ) 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 ( V on ) 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/cm 2 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. Benefiting from the solvent and device structure engineering, the blade-coated hybrid white organic light-emitting diodes (WOLEDs) reach external quantum efficiencies (EQEs) close to 12% (small-area, 0.1 cm 2 ) and 6.8% (2 cm × 2 cm) with a small amount of solution about 0.9 μL/cm 2 . • Fabricating a hybrid white organic light-emitting diodes (WOLEDs) by blade-coating at ambient conditions. • Selecting the ideal solvents (solvent engineering) and electron-transporting layer for the highly efficient blade-coating WOLED which reaches the maximum EQE, power efficiency (PE), and current efficiency (CE) of 11.6%, 30.4 lm W −1 , and 29.0 cd A −1 , respectively. • Fabricating a blade-coated WOLED (2 cm × 2 cm) owning peak EQE of 6.8% with a small amount of solution of 0.9 μL/cm 2 .