Effective charge collection area during conductive and photoconductive atomic force microscopy
Effective charge collection area during conductive and photoconductive atomic force microscopy
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DOI：
10.1063/1.5035351
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发表时间：
2018-06
影响因子：
4
通讯作者：
Haian Qiu;Xue Dong;J. Shim;Junghyun Cho;J. Mativetsky
中科院分区：
文献类型：
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作者：
Haian Qiu;Xue Dong;J. Shim;Junghyun Cho;J. Mativetsky
导电原子力显微镜(C-AFM)已被广泛应用于研究导电聚合物、纳米材料和有机电子器件的纳米尺度电学性质。虽然这些测量提供了对电性能的空间依赖性的有价值的洞察，但用C-AFM测量的电流密度和电导率始终比宏观尺度上测量的高得多。在这里，我们证明了这些异常高的电流密度和电导率是由于忽略了电流扩展而低估了载流区域。我们提出了一种在C-AFM测量过程中估算有效电荷收集面积的简单实验方法。以半导体聚合物聚3-己基噻吩膜为例，我们发现有效电荷收集面积可以比探头与薄膜之间的机械接触面积大三个数量级。得到了校准的电导图，与接受值定量对应，纳米结构有机-无机混合太阳能电池有源层的C-AFM光电流测量产生了与宏观器件报道的短路电流密度相匹配的短路电流密度。最后，我们解释了电流扩展增加了探针-样品接触尺寸之外的有效电荷收集面积，但并不排除低于10 nm的成像分辨率。导电原子力显微镜(C-AFM)已被广泛用于绘制导电聚合物、纳米材料和有机电子器件的纳米级电学性质。虽然这些测量提供了对电性能的空间依赖性的有价值的洞察，但用C-AFM测量的电流密度和电导率始终比宏观尺度上测量的高得多。在这里，我们证明了这些异常高的电流密度和电导率是由于忽略了电流扩展而低估了载流区域。我们提出了一种在C-AFM测量过程中估算有效电荷收集面积的简单实验方法。以半导体聚合物聚3-己基噻吩膜为例，我们发现有效电荷收集面积可以比探头与薄膜之间的机械接触面积大三个数量级。得到了刻度后的电导率图，并给出了定量的电导率图。
Conductive atomic force microscopy (C-AFM) has been widely used to map the nanoscale electrical properties of conducting polymers, nanomaterials, and organic electronic devices. While these measurements provide valuable insight into the spatial dependence of electrical performance, reported current densities and electrical conductivities measured by C-AFM are consistently much higher than those measured at the macroscopic scale. Here, we demonstrate that these anomalously high current densities and conductivities arise from ignoring current spreading and hence underestimating the current-carrying area. We present a simple experimental means of estimating the effective charge collection area during C-AFM measurements. Using semiconducting polymer poly(3-hexylthiophene) films as a test case, we find that the effective charge collection area can be as much as three orders of magnitude larger than the mechanical contact area between the probe and the film. Calibrated conductivity maps are obtained, with a quantitative correspondence with accepted values, and C-AFM photocurrent measurements of a nanostructured hybrid organic-inorganic solar cell active layer yield short-circuit current densities that match those reported for macroscopic devices. Finally, we address the observation that current spreading increases the effective charge collection area beyond the size of the probe-sample contact but does not preclude an imaging resolution below 10 nm.Conductive atomic force microscopy (C-AFM) has been widely used to map the nanoscale electrical properties of conducting polymers, nanomaterials, and organic electronic devices. While these measurements provide valuable insight into the spatial dependence of electrical performance, reported current densities and electrical conductivities measured by C-AFM are consistently much higher than those measured at the macroscopic scale. Here, we demonstrate that these anomalously high current densities and conductivities arise from ignoring current spreading and hence underestimating the current-carrying area. We present a simple experimental means of estimating the effective charge collection area during C-AFM measurements. Using semiconducting polymer poly(3-hexylthiophene) films as a test case, we find that the effective charge collection area can be as much as three orders of magnitude larger than the mechanical contact area between the probe and the film. Calibrated conductivity maps are obtained, with a qua...