Comparative Study of Printed Multilayer OLED Fabrication through Slot Die Coating, Gravure and Inkjet Printing, and Their Combination

Abstract

In this study, multilayer organic light-emitting diodes (OLEDs) consisting of three solution-processed layers are fabricated using slot die coating, gravure printing, and inkjet printing, techniques that are commonly used in the industry. Different technique combinations are investigated to successively deposit a hole injection layer (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)), a cross-linkable hole transport layer (N,N′-bis(4-(6-((3-ethyloxetan-3-yl)methoxy)-hexyloxy)phenyl)-N,N′-bis(4-methoxyphenyl)biphenyl-4,4′-diamin (QUPD)), and a green emissive layer (TSG-M) on top of each other. In order to compare the application techniques, the ink formulations have to be adapted to the respective process requirements. First, the influence of the application technique on the layer homogeneity of the different materials is investigated. Large area thickness measurements of the layers based on imaging color reflectometry (ICR) are used to compare the application techniques regarding the layer homogeneity and reproducible film thickness. The total stack thickness of all solution-processed layers of 32 OLEDs could be reproduced homogeneously in a process window of 30 nm for the technique combination of slot die coating and inkjet printing. The best efficiency of 13.3 cd A−1 is reached for a process combination of slot die coating and gravure printing. In order to enable a statistically significant evaluation, in total, 96 OLEDs were analyzed and the corresponding 288 layers were measured successively to determine the influence of layer homogeneity on device performance.

Rapid and high-resolution patterning of microstructure and composition in organic semiconductors using ‘molecular gates’

“…In terms of throughput, for instance in the context of OLEDs, typical material deposition speeds by inkjet printing, slot-die coating and gravure printing are in the 0.1-5 m s −1 range 23 . Evidently, the speeds used in this first demonstration of molecular-gate-based patterning (≤3 mm s −1 ) fall short of those for these established techniques.…”

“…4,6 . These can be broadly classified into light-based methods such as photolithography 16 and laser-induced forward transfer (LIFT) 17,18 ; printing methods such as inkjet, vapour jet and aerosol jet [19][20][21][22][23] , and contact methods such as hard and soft imprint lithography [24][25][26] . Of these, photolithography represents the most mature technology, with a further advantage being its high spatial resolution (~1 μm in large-field proximity-mode implementations).…”

All solution-processed ITO free flexible organic light-emitting diodes

“…[10][11][12] More studies can be found based on sheet-tosheet printing processes. [13][14][15][16][17][18][19] But only a few studies reported all solution-processed OLEDs compared to OPVs. [20][21][22][23][24][25] The choice of the materials is the first step to address a lowcost R2R fabrication process.…”

Interlayer Engineering of Flexible and Large Area Red Organic Light Emitting Diodes Based on a N-Annulated Perylene Diimide Dimer

“…The large area coating of organic electronic devices is an active research area due to the potential to deliver next-generation printed electronics at ultra-low costs. Roll-to-roll and pattern coatings are the most common methods used for the fabrication of multi-layer organic electronic devices such as organic-light-emitting-diodes (OLEDs) 1 , photovoltaics 2 , sensors 3 , and transistors 4 . One of the most user-friendly and inexpensive methods is slot-die coating.…”