Surface-Segregated Monolayers: A New Type of Ordered Monolayer for Surface Modification of Organic Semiconductors

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• 作者：Qingshuo Wei ; Keisuke Tajima ; Yujin Tong ; Shen Ye ; Kazuhito Hashimoto
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：December 9, 2009
• 年：2009
• 卷：131
• 期：48
• 页码：17597-17604
• 全文大小：358K
• 年卷期：v.131,no.48(December 9, 2009)
• ISSN：1520-5126

文摘

We report a new type of ordered monolayer for the surface modification of organic semiconductors. Fullerene derivatives with fluorocarbon chains ([6,6]-phenyl-C₆₁-buryric acid 1H,1H-perfluoro-1-alkyl ester or FC_n) spontaneously segregated as a monolayer on the surface of a [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) film during a spin-coating process from the mixture solutions, as confirmed by X-ray photoelectron spectroscopy (XPS). Ultraviolet photoelectron spectroscopy (UPS) showed the shift of ionization potentials (IPs) depending on the fluorocarbon chain length, indicating the formation of surface dipole moments. Surface-sensitive vibrational spectroscopy, sum frequency generation (SFG) revealed the ordered molecular orientations of the C₆₀ moiety in the surface FC_n layers. The intensity of the SFG signals from FC_n on the surface showed a clear odd−even effect when the length of the fluorocarbon chain was changed. This new concept of the surface-segregated monolayer provides a facile and versatile approach to modifying the surface of organic semiconductors and is applicable to various organic optoelectronic devices.