Interface Energy Alignment of Atomic-Layer-Deposited VOx on Pentacene: an in Situ Photoelectron Spectroscopy Investigation

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• 作者：Ran ZhaoYuanhong Gao ; Zheng Guo ; Yantao Su ; Xinwei Wang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2017
• 出版时间：January 18, 2017
• 年：2017
• 卷：9
• 期：2
• 页码：1885-1890
• 全文大小：409K
• ISSN：1944-8252

文摘

Ultrathin atomic-layer-deposited (ALD) vanadium oxide (VO_x) interlayer has recently been demonstrated for remarkably reducing the contact resistance in organic electronic devices (Adv. Funct. Mater. 2016, 26, 4456). Herein, we present an in situ photoelectron spectroscopy investigation (including X-ray and ultraviolet photoelectron spectroscopies) of ALD VO_x grown on pentacene to understand the role of the ALD VO_x interlayer for the improved contact resistance. The in situ photoelectron spectroscopy characterizations allow us to monitor the ALD growth process of VO_x and trace the evolutions of the work function, pentacene HOMO level, and VO_x defect states during the growth. The initial VO_x growth is found to be partially delayed on pentacene in the first ∼20 ALD cycles. The underneath pentacene layer is largely intact after ALD. The ALD VO_x is found to contain a high density of defect states starting from 0.67 eV below the Fermi level, and the energy level of these defect states is in excellent alignment with the HOMO level of pentacene, which therefore allows these VO_x defect states to provide an efficient hole-injection pathway at the contact interface.