Multi-Charged Conjugated Polyelectrolytes as a Versatile Work Function Modifier for Organic Electronic Devices
Multi-Charged Conjugated Polyelectrolytes as a Versatile Work Function Modifier for Organic Electronic Devices
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DOI：
10.1002/adfm.201301810
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发表时间：
2014-02-01
影响因子：
19
通讯作者：
Lee, Kwanghee
中科院分区：
文献类型：
--
作者：
Lee, Byoung Hoon;Jung, In Hwan;Lee, Kwanghee
尽管共轭聚电解质（CPE）具有优异的功函数可调性，其通过在CPE/金属电极界面处形成永久偶极子来诱导真空能级移动，但是通过CPE电子传输层（ETL）的电子注入的确切机制仍然不清楚。特别是，了解克服相当大的注入障碍时CPE ETL内的离子运动是一个重大的挑战。由于CPE的离子功能是这些功能的关键组成部分，因此使用CPE中高度受控的离子密度（ID）进行严格分析对于理解潜在机制至关重要。在这里，通过引入一系列新的CPE与各种数量的离子功能，在这样的界面处的能级调谐可以直接通过调整的ID在CPE确定。更重要的是，这些系列CPE表明，根据CPE厚度，必须调用两种不同的机制。永久性界面偶极子的形成对于通过CPE ETL（10 nm，量子力学隧穿极限）的电子注入是关键的，而通过厚CPE ETL（20-30 nm）的电子注入由给定电场下离子侧链的重取向主导。
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.