TY - JOUR
T1 - Multi-charged conjugated polyelectrolytes as a versatile work function modifier for organic electronic devices
AU - Lee, Byoung Hoon
AU - Jung, In Hwan
AU - Woo, Han Young
AU - Shim, Hong Ku
AU - Kim, Geunjin
AU - Lee, Kwanghee
N1 - Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.
PY - 2014/2/26
Y1 - 2014/2/26
N2 - Despite the excellent work function adjustability of conjugated polyelectrolytes (CPEs), which induce a vacuum level shift via the formation of permanent dipoles at the CPE/metal electrode interface, the exact mechanism of electron injection through the CPE electron transport layer (ETL) remains unclear. In particular, understanding the ionic motion within the CPE ETLs when overcoming the sizable injection barrier is a significant challenge. Because the ionic functionality of CPEs is a key component for such functions, a rigorous analysis using highly controlled ion density (ID) in CPEs is crucial for understanding the underlying mechanism. Here, by introducing a new series of CPEs with various numbers of ionic functionalities, energy level tuning at such an interface can be determined directly by adjusting the ID in the CPEs. More importantly, these series CPEs indicate that two different mechanisms must be invoked according to the CPE thickness. The formation of permanent interfacial dipoles is critical with respect to electron injection through CPE ETL (≤ 10 nm, quantum mechanical tunneling limit), whereas electron injection through thick CPE ETL (20-30 nm) is dominated by the reorientation of the ionic side chains under a given electric field. An electron injection mechanism for conjugated polyelectrolyte (CPE) electron transport layers in organic electronic devices is demonstrated by introducing a new series of CPEs with various numbers of ionic functionalities. Energy level tuning at the CPE/metal interface can be determined directly by adjusting ion density in the CPEs. Thickness-dependent electron injection characteristics indicate that two different mechanisms must be invoked according to the CPE thickness.
AB - Despite the excellent work function adjustability of conjugated polyelectrolytes (CPEs), which induce a vacuum level shift via the formation of permanent dipoles at the CPE/metal electrode interface, the exact mechanism of electron injection through the CPE electron transport layer (ETL) remains unclear. In particular, understanding the ionic motion within the CPE ETLs when overcoming the sizable injection barrier is a significant challenge. Because the ionic functionality of CPEs is a key component for such functions, a rigorous analysis using highly controlled ion density (ID) in CPEs is crucial for understanding the underlying mechanism. Here, by introducing a new series of CPEs with various numbers of ionic functionalities, energy level tuning at such an interface can be determined directly by adjusting the ID in the CPEs. More importantly, these series CPEs indicate that two different mechanisms must be invoked according to the CPE thickness. The formation of permanent interfacial dipoles is critical with respect to electron injection through CPE ETL (≤ 10 nm, quantum mechanical tunneling limit), whereas electron injection through thick CPE ETL (20-30 nm) is dominated by the reorientation of the ionic side chains under a given electric field. An electron injection mechanism for conjugated polyelectrolyte (CPE) electron transport layers in organic electronic devices is demonstrated by introducing a new series of CPEs with various numbers of ionic functionalities. Energy level tuning at the CPE/metal interface can be determined directly by adjusting ion density in the CPEs. Thickness-dependent electron injection characteristics indicate that two different mechanisms must be invoked according to the CPE thickness.
KW - conjugated polyelectrolytes
KW - ionic motion
KW - organic electronics
KW - work function tuning
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U2 - 10.1002/adfm.201301810
DO - 10.1002/adfm.201301810
M3 - Article
AN - SCOPUS:84894415143
VL - 24
SP - 1100
EP - 1108
JO - Advanced Functional Materials
JF - Advanced Functional Materials
SN - 1616-301X
IS - 8
ER -