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Electrospray deposition of polymer thin films for organic light-emitting diodes.

Hwang W, Xin G, Cho M, Cho SM, Chae H - Nanoscale Res Lett (2012)

Bottom Line: PLED devices made by an electrospray process were compared with spin-coated ones.PLED devices made by the electrospray process showed lower current density than that of spin-coated ones.The PL peak shift and reduced current of electrosprayed films can therefore be attributed to the conformation of the polymer.

View Article: PubMed Central - HTML - PubMed

Affiliation: SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University (SKKU), Suwon, 440-746, South Korea. hchae@skku.edu.

ABSTRACT
Electrospray process was developed for organic layer deposition onto polymer organic light-emitting diode [PLED] devices in this work. An electrospray can be used to produce nanometer-scale thin films by electric repulsion of microscale fine droplets. PLED devices made by an electrospray process were compared with spin-coated ones. The PLED device fabricated by the electrospray process showed maximum current efficiency of 24 cd/A, which was comparable with that of the spin-coating process. The electrospray process required a higher concentration of hole and electron transport materials in the inks than spin-coating processes to achieve PLED maximum performance. Photoluminescence [PL] at 407 nm was observed using electrosprayed poly(N-vinyl carbazole) films, whereas a peak at 410 nm was observed with the spin-coated ones. Similar difference in peak position was observed between aromatic and nonaromatic solvents in the spin-coating process. PLED devices made by the electrospray process showed lower current density than that of spin-coated ones. The PL peak shift and reduced current of electrosprayed films can therefore be attributed to the conformation of the polymer.

No MeSH data available.


Schematic description of the electrospray process used for PLED fabrication.
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Figure 1: Schematic description of the electrospray process used for PLED fabrication.

Mentions: The layer structure of the devices was as follows: indium tin oxide [ITO]/poly(3, 4-ethylenedioxythiophene) poly(styrenesulfonate) [PEDOT:PSS]/active layer/metal cathode. A hole-injection PEDOT:PSS layer of 30-nm thick was first spin-coated on pre-cleaned ITO substrates and then baked at 120°C for 20 min. About 80-nm-thick emissive layer [EML] was formed by electrospray or spin-coating process and then annealed at 80°C for 30 min. A schematic diagram of the experimental setup for the electrospray process is shown in Figure 1. For the electrospray process, the blend ink was injected through the nozzle at a rate of 30 μl/min, and about 3 kV was applied to break the meniscus formed at the tip of the nozzle. The distance between the tip of the nozzle (150 μm in diameter) and the substrate was maintained at 3 to 4 cm. During spraying, the nozzle and substrate were fixed, and the thickness of EML was controlled by varying the deposition time. For the comparative spin-coating process, the solution was spin-coated at 2, 000 rpm for 20 s. All the experiments were carried out at 20°C to 25°C and a humidity of 30% to 35%. The interlayer and cathode were thermally evaporated on the top of the EML at a pressure of 2 × 10-5 Torr.


Electrospray deposition of polymer thin films for organic light-emitting diodes.

Hwang W, Xin G, Cho M, Cho SM, Chae H - Nanoscale Res Lett (2012)

Schematic description of the electrospray process used for PLED fabrication.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3275458&req=5

Figure 1: Schematic description of the electrospray process used for PLED fabrication.
Mentions: The layer structure of the devices was as follows: indium tin oxide [ITO]/poly(3, 4-ethylenedioxythiophene) poly(styrenesulfonate) [PEDOT:PSS]/active layer/metal cathode. A hole-injection PEDOT:PSS layer of 30-nm thick was first spin-coated on pre-cleaned ITO substrates and then baked at 120°C for 20 min. About 80-nm-thick emissive layer [EML] was formed by electrospray or spin-coating process and then annealed at 80°C for 30 min. A schematic diagram of the experimental setup for the electrospray process is shown in Figure 1. For the electrospray process, the blend ink was injected through the nozzle at a rate of 30 μl/min, and about 3 kV was applied to break the meniscus formed at the tip of the nozzle. The distance between the tip of the nozzle (150 μm in diameter) and the substrate was maintained at 3 to 4 cm. During spraying, the nozzle and substrate were fixed, and the thickness of EML was controlled by varying the deposition time. For the comparative spin-coating process, the solution was spin-coated at 2, 000 rpm for 20 s. All the experiments were carried out at 20°C to 25°C and a humidity of 30% to 35%. The interlayer and cathode were thermally evaporated on the top of the EML at a pressure of 2 × 10-5 Torr.

Bottom Line: PLED devices made by an electrospray process were compared with spin-coated ones.PLED devices made by the electrospray process showed lower current density than that of spin-coated ones.The PL peak shift and reduced current of electrosprayed films can therefore be attributed to the conformation of the polymer.

View Article: PubMed Central - HTML - PubMed

Affiliation: SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University (SKKU), Suwon, 440-746, South Korea. hchae@skku.edu.

ABSTRACT
Electrospray process was developed for organic layer deposition onto polymer organic light-emitting diode [PLED] devices in this work. An electrospray can be used to produce nanometer-scale thin films by electric repulsion of microscale fine droplets. PLED devices made by an electrospray process were compared with spin-coated ones. The PLED device fabricated by the electrospray process showed maximum current efficiency of 24 cd/A, which was comparable with that of the spin-coating process. The electrospray process required a higher concentration of hole and electron transport materials in the inks than spin-coating processes to achieve PLED maximum performance. Photoluminescence [PL] at 407 nm was observed using electrosprayed poly(N-vinyl carbazole) films, whereas a peak at 410 nm was observed with the spin-coated ones. Similar difference in peak position was observed between aromatic and nonaromatic solvents in the spin-coating process. PLED devices made by the electrospray process showed lower current density than that of spin-coated ones. The PL peak shift and reduced current of electrosprayed films can therefore be attributed to the conformation of the polymer.

No MeSH data available.