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Characteristics of Solution‐Processed Small‐Molecule Organic Films and Light‐Emitting Diodes Compared with their Vacuum‐Deposited Counterparts
Author(s) -
Lee TaeWoo,
Noh Taeyong,
Shin HeeWon,
Kwon Ohyun,
Park JongJin,
Choi ByoungKi,
Kim MyeongSuk,
Shin Dong Woo,
Kim YongRok
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200801045
Subject(s) - oled , materials science , optoelectronics , layer (electronics) , diode , solution process , luminous efficacy , vacuum deposition , small molecule , ultra high vacuum , molecule , nanotechnology , organic chemistry , chemistry , biochemistry
Although significant progress has been made in the development of vacuum‐deposited small‐molecule organic light‐emitting diodes (OLEDs), one of the most desired research goals is still to produce flexible displays by low‐cost solution processing. The development of solution‐processed OLEDs based on small molecules could potentially be a good approach but no intensive studies on this topic have been conducted so far. To fabricate high‐performance devices based on solution‐processed small molecules, the underlying nature of the produced films and devices must be elucidated. Here, the distinctive characteristics of solution‐processed small‐molecule films and devices compared to their vacuum‐deposited counterparts are reported. Solution‐processed blue OLEDs show a very high luminous efficiency (of about 8.9 cd A –1 ) despite their simplified structure. A better hole‐blocking and electron‐transporting layer is essential for achieving high‐efficiency solution‐processed devices because the solution‐processed emitting layer gives the devices a better hole‐transporting capability and more electron traps than the vacuum‐deposited layer. It is found that the lower density of the solution‐processed films (compared to the vacuum‐deposited films) can be a major cause for the short lifetimes observed for the corresponding devices.