OLED Inkjet Printing
The OLED inkjet printing uses solvents to melt OLED organic materials and subsequently prints materials on the surface of substrates to form R (red), G (green), and B (blue) organic light-emitting layers. Learn more at https://semiconductor.alfachemic.com/product/silver-nanoparticles-ink-for-inkjet-printing-334550.html
The OLED inkjet printing uses solvents to melt OLED organic materials and subsequently prints materials on the surface of substrates to form R (red), G (green), and B (blue) organic light-emitting layers. Learn more at https://semiconductor.alfachemic.com/product/silver-nanoparticles-ink-for-inkjet-printing-334550.html
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
OLED Inkjet Printing
The OLED inkjet printing uses solvents to melt OLED organic materials and subsequently prints
materials on the surface of substrates to form R (red), G (green), and B (blue) organic
light-emitting layers.
Inkjet Printing Polymer Materials
Due to the greater molecular weight of polymers, solution processing was mainly used to form
films, such as spin coating or printing, while inkjet printing technology has proven to be the most
efficient method for preparing light-emitting polymer solutions. In 1990, Richard Friend et al.
discovered the electroluminescence properties of polymers in Cavendish Laboratory at the
University of Cambridge and invented the polymer light-emitting diode (PLED). Since then, PLED
display has attracted great attention and demonstrated considerable potential for manufacturing
next-generation flat-panel displays.
Inkjet Printing of Small Molecule Materials
At present, the efficiency (6-8cd/A) and the lifetime of polymer light-emitting devices (PLEDs) are
generally low. Small-molecule light-emitting devices (SM-OLEDs) possess obvious performance
advantages, such as higher efficiency (84cd/A) and a longer lifespan. Although PLEDs possess
limitations in their application use, multilayer phosphorescent SM-OLEDs fabricated through the
thermal evaporation process can achieve higher efficiency to overcome certain limitations.
In one study, Xia et al. created thin films of these traditional thermally evaporated small-molecule
materials by inkjet printing and prepared phosphorescent small-molecule light-emitting devices
with better performance. As a result, obtaining high-quality functional thin films remains
necessary for fabricating efficient and long-life devices, while available small molecule materials
have poor film-forming properties. During the drying process of the liquid film on the substrate, it
is easy to form a discontinuous film. In this regard, there are two primary methods to improve
the film-forming properties of small molecules. First, the molecular volume can be upregulated
by modifying the alkyl chain length to design and synthesize molecules of good solubility and
film-forming properties; Second, polymer materials can be added to small molecular materials to
enhance film-forming properties.
In addition, modifying the physical and chemical properties of the substrate surface can improve
the film-forming properties of materials. Sirringhaus et al. inkjet printed water-soluble materials
on the surface of hydrophilic substrates patterned with hydrophobic materials and obtained
high-resolution polymer electrodes. Hendriks et al. printed nano-silver ink wires on a hot-pressed
engraved substrate surface. Since the contact angle was small, the ink was drawn into the
channel by capillary action, especially the fluid properties of small molecule solutions mainly
depend on the properties of solvents. Although the effect of solvents on the film-forming
properties of small molecules has been extensively studied, they still remain complicated.
Inkjet Printed Cathodes
Similar to the principle of evaporating small molecules, the cathodes of OLED devices are
generally produced through the vacuum evaporation process, but the evaporation equipment
and masks required are expensive. Using inkjet printing technology to prepare cathodes can
greatly reduce cost, but alternative problems such as uniform film formation within a large area
remain a major challenge. Based on the preliminary research about the OLED display through the
full printing process, the major factors toward development are printable cathode ink and
large-area film formation technology. The main difficulty lies in the affinity between the cathode
material and the organic functional layer, which is required to form a stable film for the printed
cathode. Additionally, the fineness of the printed pattern must be guaranteed to provide a
high-resolution image. As a result, the destruction of the bottom layer by the cathode paste must
be avoided. The effective injection of carriers must be ensured to guarantee top-grade brightness
and high display performance. These requirements should be met to ensure high brightness and
high-efficiency display performance.
The OLED functional layer requires a uniform standard for film thickness and should retain
optoelectronic properties for easy solvent drying and removal during the film formation process.
Similarly, other additives in ink need also to be removed with minimum interference on the
performance of the organic semiconductor film. This development of OLED display technology
through inkjet printing not only furthers the development of inkjet printers and print heads but
also attracts growing attention and research on related topics such as ink formulation,
ink/substrate interface contact characteristics, and the drying process.
The solution for the inkjet printing OLED display is mainly composed of optoelectronic materials
and solvents. It is necessary to consider the preparation of ink through the various processes
related to fluid characteristics, degrees of spreading, and the drying process in film formation.
The printability of ink is primarily determined by the amount of viscosity, surface tension, and
shear rate variation, while the molecular structure and molecular weight, solids content, and
choice of solvent are the main factors that produce these physical parameters. Alfa Chemistry is
one of the leading suppliers of photochemistry products, ranging from fluorophores, fluorescent
probes, luminescence material, photosensitizers, and photocatalysts, to quantum dots. Alfa
Chemistry also provides chemicals and materials like zinc oxide ink, aluminum-doped zinc oxide
ink, molybdenum disulfide ink, and silver nanoparticle ink for inkjet printing.