Efficient small molecule organic light-emitting diodes fabricated by brush-coating

Abstract

With the ongoing progress in exploring novel fabrication methods, topics towards high-performance, simply fabricated organic light-emitting diodes (OLEDs) have received a great deal of attention. Brush-coating is a superior liquid phase thin film deposition technology with nearly 100% material utilization, which has remarkable potential application in depositing large-area uniform films. Here, a uniform and smooth polymer hole-injection layer and a small molecule light-emitting layer are successfully fabricated through brush-coating by controlling the wetting and dewetting processes. White phosphorescent OLEDs with blue and orange complementary colours are constructed by continuously brush-coating the hole-injection layer and small molecule light-emitting layer. The brush-coated white device possesses a peak luminance of 29 190 cd m⁻² and a current efficiency of 29.3 cd A⁻¹, which are comparable to those of the spin-coated device with the same structure. In addition, the brush-coated red, green and blue phosphorescent OLEDs exhibit excellent performance in our research with peak current efficiencies of 16.7, 30.4 and 20.9 cd A⁻¹, respectively. These results demonstrate that the brush-coating technology is a simple and effective strategy for depositing uniform organic films and, consequently, fabricating a high-performance device. What's more, brush-coating is expected to be applied to the best-to-date, large-area, flexible or patterned OLEDs in the future.