High-Efficiency and Robust PhOLEDs Fabricated by Blade-Coated Planar Source Evaporation

Planar source evaporation (PSE) is a promising technology for fabricating organic light-emitting diodes (OLEDs) devices due to its high material utilization, low-temperature accessibility, and minimized shadow effect, which should have led to low-cost fabrication, efficient light emission, and high resolution. However, PSE-OLEDs have been struggling with poor performance and stability due to an unclear photoelectric mechanism caused by distinct film formation with PSE. In this work, an innovative method of blade-coated PSE (BCPSE) is proposed to realize easily-accessible phosphorescent OLEDs with micro-ternary doped emitting layer. Based on it, comprehensive analysis on morphology, optoelectrical properties, and carrier dynamics reveal the superior electrical and optical properties caused by distinct film formation with PSE including better equilibrium of carriers, decreased nonradiative recombination loss, and reduction of exciton-polaron annihilation aroused by BCPSE, thus resulting in comparable efficiency and promoted half-life time (maximum current efficiency CE<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>max</roman></sub> = 25.9 cd/A, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>50</roman></sub> = 54 306 h@100 cd/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sup>) compared to device produced with vacuum thermal evaporation (VTE) (CE<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>max</roman></sub> = 22.8 cd/A, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>50</roman></sub> = 17 149 h@100 cd/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sup>). BCPSE not only reduces fabrication cost but also improves device stability, positioning it as a promising method for next-generation OLED applications.