A Novel Blade‐Jet Coating Method for Achieving Ultrathin, Uniform Film toward All‐Solution‐Processed Large‐Area Organic Light‐Emitting Diodes

Abstract

This paper reports a new type of large‐area solution coating method that combines a blade coating process and an air‐jet finishing process, and its application to soluble organic light‐emitting diodes (OLEDs) fabrication. The blade coating with stable coating conditions results in a relatively thick uniform wet film. Air‐jet finishing subsequently adjusts the wet film to the target thickness by precisely controlling the flow of the coating solution. By hybridizing the blade coating method and air‐jet finishing technique, functional thin‐film layers can be produced with outstanding quality in terms of thickness uniformity and controllability with high reproducibility. In particular, the blade–jet coating method enables the fabrication of an ultrathin electron injection layer (EIL) of Cs2CO3 at less than a few nanometer scale over a large area by a solution process. The superior performance of the blade–jet coating method enables solution‐processed large‐area OLED fabrication on both rigid and flexible substrates, with outstanding light‐emitting uniformity. Furthermore, by controlling the thickness and interfacial properties of the EIL, device performance can be optimized. The luminous power efficiency of the optimum OLED device is 8.42 lm W−1, and the luminous nonuniformity is only 2.68% at 6 V over a large area.

Inkjet Printing of Super Yellow: Ink Formulation, Film Optimization, OLEDs Fabrication, and Transient Electroluminescence

“…The printed OLEDs with 70 nm thick Super Yellow layer have shown the highest maximum luminescence of 64,000 cd/m 2 . The value of maximum luminescence achieved here exceeds previously reported values for SY OLEDs partially fabricated by printing 22,46 . Comparing with SY OLEDs fabricated by spin-coating, maximum luminescence of our printed devices is the same as of our spin-coated devices, and is state-of-the-art 47 .…”

Inkjet Printing of an Electron Injection Layer: New Role of Cesium Carbonate Interlayer in Polymer OLEDs

“…The spin-coated Cs 2 CO 3 also forms efficient electron injection interlayer and PLEDs displayed slightly higher current efficiency than the PLEDs with Ca/Al, indicating the potential application for printable electronic devices. Our results are similar to Super Yellow-based PLEDs previously recorded in literature [ 60 , 61 ].…”

“…The spin-coated Cs 2 CO 3 also forms efficient electron injection interlayer and PLEDs displayed slightly higher current efficiency than the PLEDs with Ca/Al, indicating the potential application for printable electronic devices. Our results are similar to Super Yellow-based PLEDs previously recorded in literature [60,61]. The PLEDs with printed Cs 2 CO 3 performed better than the PLEDs without Cs 2 CO 3 showing a fourfold increase higher brightness and twenty-fold increase in current efficiency.…”

Metal halide perovskite nanocrystals: application in high-performance photodetectors

“…At present, it has been widely used in the preparation of photovoltaic and photoelectric devices. [91][92][93][94] When using the doctor blading process, the slurry mixed evenly is placed on the side of the substrate close to the blade, and the blade passes through the surface of the substrate uniformly to spread the solution on the substrate. Usually, the film thickness can reach hundreds of microns, which is affected by the concentration of solution, the surface energy of substrate, coating speed ang the gap between scraper and substrate.…”