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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.


Related in: MedlinePlus

Current density-voltage curve of PVK devices using spin-coating and electrospray deposition (ITO/PEDOT:PSS/PVK/CsF/Al). The thin films using CB/DCB showed a better current density under the same conditions.
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Figure 5: Current density-voltage curve of PVK devices using spin-coating and electrospray deposition (ITO/PEDOT:PSS/PVK/CsF/Al). The thin films using CB/DCB showed a better current density under the same conditions.

Mentions: To investigate the difference between electrospray and spin-coating processes, PVK thin films were formed by two different processes, and their electric and PL characteristics were investigated. As mentioned earlier, development of a proper solvent is an important step in the electrospray process. Accordingly, we also investigated the effects of solvents on electric and PL film characteristics. Figure 4 shows the effects of solvents and process method on PL characteristics. We chose two different types of solvents: an aromatic solvent which comprised a mixture of CB and DCB and non-aromatic solvents, chloroform [CF] and 1, 2-dichloroethane [DCE]. The mixture of CB and DCB was selected as it was optimum for our device structure and process. The PL peaks of the thin films were observed at 407 nm with CF and DCE and at 410 nm with the aromatic solvent mixture. Using the same aromatic solvent, PVK films processed by the electrospray process showed PL peaks at 407 nm, while those made by spin-coating showed PL peaks at 410 nm. Qian et al. [19] reported a peak shift of PVK due to polymer conformation caused by the solvent effect. We believe that a similar polymer conformation effect results not only from the solvent, but also from the processing method as shown in this work. Figure 5 shows the current-voltage characteristics of the PVK film using different solvents and processing methods. At the same thickness, the thin films using the aromatic solvent (mixture of CB and DCB) showed a higher current density than those processed with the DCE nonaromatic solvent. In terms of processing methods, the PVK film processed with the electrospray method showed a lower current density than that of spin-coated ones. These results suggest that polymer conformation of PVK thin films was affected by the processing method as well as by the solvent's molecular structure as also indicated in PL results in Figure 4. Based on these results, we speculate that the properties of thin films made by the electrospray process are similar to those of spin-coated films made with DCE.


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)

Current density-voltage curve of PVK devices using spin-coating and electrospray deposition (ITO/PEDOT:PSS/PVK/CsF/Al). The thin films using CB/DCB showed a better current density under the same conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Current density-voltage curve of PVK devices using spin-coating and electrospray deposition (ITO/PEDOT:PSS/PVK/CsF/Al). The thin films using CB/DCB showed a better current density under the same conditions.
Mentions: To investigate the difference between electrospray and spin-coating processes, PVK thin films were formed by two different processes, and their electric and PL characteristics were investigated. As mentioned earlier, development of a proper solvent is an important step in the electrospray process. Accordingly, we also investigated the effects of solvents on electric and PL film characteristics. Figure 4 shows the effects of solvents and process method on PL characteristics. We chose two different types of solvents: an aromatic solvent which comprised a mixture of CB and DCB and non-aromatic solvents, chloroform [CF] and 1, 2-dichloroethane [DCE]. The mixture of CB and DCB was selected as it was optimum for our device structure and process. The PL peaks of the thin films were observed at 407 nm with CF and DCE and at 410 nm with the aromatic solvent mixture. Using the same aromatic solvent, PVK films processed by the electrospray process showed PL peaks at 407 nm, while those made by spin-coating showed PL peaks at 410 nm. Qian et al. [19] reported a peak shift of PVK due to polymer conformation caused by the solvent effect. We believe that a similar polymer conformation effect results not only from the solvent, but also from the processing method as shown in this work. Figure 5 shows the current-voltage characteristics of the PVK film using different solvents and processing methods. At the same thickness, the thin films using the aromatic solvent (mixture of CB and DCB) showed a higher current density than those processed with the DCE nonaromatic solvent. In terms of processing methods, the PVK film processed with the electrospray method showed a lower current density than that of spin-coated ones. These results suggest that polymer conformation of PVK thin films was affected by the processing method as well as by the solvent's molecular structure as also indicated in PL results in Figure 4. Based on these results, we speculate that the properties of thin films made by the electrospray process are similar to those of spin-coated films made with DCE.

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.


Related in: MedlinePlus