27 August 2009 Interface study of insertion layers in organic semiconductor devices
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Abstract
Inserting an ultra-thin interlayer has been an important means in modifying the performance of organic semiconductor devices. Using photoemission and inverse photoemission spectroscopy (UPS, XPS and IPES), we have investigated the electronic structure of a number of insertion layers widely used in organic semiconductor devices. We found that inserting alkali metal compound thin layers such as LiF between the electron transport layer (ETL) and the cathode can induce energy level shift in the ETL that reduces the electron injection barrier. The reduction is attributed to the release of the alkali metal that n-doped the ETL, and as such it depends on the cathode material deposited on top of the insertion layer. For thin metal oxide insertion layers, such as MoO3, between the anode and the hole transport layer (HTL), reduction of the hole injection barrier is also observed. This reduction, however, is due to the large workfunction of the oxide that subsequently moves the highest occupied molecular orbital (HOMO) toward the anode Fermi level. Effects of other insertion layers, such as metal insertion layer in organic bistable device (OBD) and organic insertion layer in bipolar organic thin film transistors (OTFT) will also be discussed.
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Huanjun Ding, " Irfan, Franky So, Yongli Gao, "Interface study of insertion layers in organic semiconductor devices", Proc. SPIE 7415, Organic Light Emitting Materials and Devices XIII, 74150J (27 August 2009); doi: 10.1117/12.829333; https://doi.org/10.1117/12.829333
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