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

Abstract

Flexible red OLEDs based on a quadruple-layer stack, in between electrodes, with 160 mm 2 active area were fabricated in ambient air on PET via slotdie-coating. For the OLED structure PET/ITO/PEDOT:PSS/PVK/PFO:tPDI 2 N-EH/ZnO/Ag, the ink formulations and coating parameters for each layer were systematically evaluated and optimized. The air-stable red-light-emitting material tPDI 2 N-EH was successfully utilized as blended homogeneous film with PFO for the emitting layer. The use of an organic hole-transport layer (PVK) and inorganic electron injection layer (ZnO) significantly improved the brightness of the reference device from 4 to 303 cd/m 2 . Surface analysis using AFM measurements showed that the PVK interlayer reduced the surface roughness of the hole injection layer (PEDOT:PSS) from 0.45 to 0.17 nm, which improved the ability to form uniform emitting layers on top. In addition, the ZnO interlayer decreased surface roughness from 1.26 to 0.85 nm and reduced the turn-on voltage of the device from 5.0 to 2.8 V.

Synthesis, characterization and use of benzothioxanthene imide based dimers

“…Moreover, the performance of these BTXI-based OLEDs could be improved by using a multilayer OLEDs structure. 12…”

Organic light emitting diodes (OLEDs) with slot-die coated functional layers

“…Slot-die coating, among many printing/coatings techniques, is widely used to fabricate electronic devices including OLEDs [41][42][43] , Organic Photovoltaics (OPVs) [44][45][46] Sensors [47][48][49] , and Organic Thin Film Transistors (OTFTs) [50][51][52] . It is a low-cost coating method that can easily be adapted to continuous roll-to-roll processing and is effective in delivering large area and uniform thin-films.…”

“…QUPD is N,N¢-bis(4-(6-((3-ethyloxetan-3-yl)methoxy) hexyloxy)phenyl)-N,N¢-bis(4-methoxyphenyl)biphenyl-4,4¢-diamine, TSG-M is green emitter. (reproduced from the reference95 ).Rahmati et al42 presented the slot-die coating of four organic layers for the fabrication of flexible red OLEDs. The OLED structure consisted of: PET/ITO/PEDOT:PSS/PVK/PFO:tPDI2NEH/ZnO/Ag.…”

“…Comparison of the different OLEDs performance (reproduced with the performance from the reference42 ). Summary of single, double, triple and quadruple layer slot-die coated OLEDs.…”

Improved performance of solution processed OLEDs using N-annulated perylene diimide emitters with bulky side-chains

“…Such larger oligomers and/or starburst derivatives can reduce co-facial pi-pi stacking and limit ACQ. 14 Recently, the Welch group has reported on a series of N-annulated PDI dimers with controlled aggregation tendencies 15 and green solvent processability 16 that have found utility in both organic solar cells [17][18][19][20] and OLEDs 21,22 . These compounds are readily made on scale, are highly soluble in common organic processing solvents, and exhibit a range of optoelectronic properties.…”