High-Resolution Kelvin Probe Force Microscopy Imaging of Interface Dipoles and Photogenerated Charges in Organic Donor–Acceptor Photovoltaic Blends

详细信息    查看全文

• 作者：Franz Fuchs ; Florent Caffy ; Renaud Demadrille ; Thierry Mélin ; Benjamin Grévin
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：January 26, 2016
• 年：2016
• 卷：10
• 期：1
• 页码：739-746
• 全文大小：624K
• ISSN：1936-086X

文摘

We present noncontact atomic force microscopy and Kelvin probe force microscopy studies of nanophase segregated photovoltaic blends based on an oligothiophene–fluorenone oligomer and [6,6]-phenyl C70 butyric acid methyl ester. We carried out a complete analysis of the influence of the tip–surface interaction regime on the topographic, in-dark contact potential and surface photovoltage contrasts. It is demonstrated that an optimal lateral resolution is achieved for all channels below the onset of a contrast in the damping images. With the support of electrostatic simulations, it is shown that in-dark contact potential difference contrasts above subsurface acceptor clusters are consistent with an uneven distribution of permanent charges at the donor–acceptor interfaces. A remarkable dependence of the surface photovoltage magnitude with respect to the tip–surface distance is evidenced and attributed to a local enhancement of the electromagnetic field at the tip apex.