Department of Materials Science and Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.
Proc Natl Acad Sci U S A. 2010 Mar 2;107(9):3972-6. doi: 10.1073/pnas.0910554107. Epub 2010 Feb 16.
The operation of organic diodes in solar cells and light-emitting displays strongly depends on the properties of the interfaces between hole- and electron-carrying organic semiconductors. Such interfaces are difficult to characterize, as they are usually buried under the surface or exist as an irregular "bulk heterojunction." Using a unique fluorinated barrier layer-based lithographic technique, we fabricated a lateral organic p-n junction, allowing the first observation of the potential at an organic p-n interface simultaneously with the charge transport measurements. We find that the diode characteristics of the device (current output and rectification ratio) are consistent with the changes in the surface potentials near the junction, and the current-voltage curves and junction potentials are strongly and self-consistently modulated by a third, gate electrode. The generality of our technique makes this an attractive method to investigate the physics of organic semiconductor junctions. The lithographic technique is applicable to a wide variety of soft material patterns. The observation of built-in potentials makes an important connection between organic junctions and textbook descriptions of inorganic devices. Finally, these kinds of potentials may prove to be controlling factors in charge separation efficiency in organic photovoltaics.
有机二极管在太阳能电池和发光显示器中的工作性能强烈依赖于空穴和电子传输有机半导体之间界面的性质。这些界面很难进行表征，因为它们通常被掩埋在表面之下，或者以不规则的“体异质结”形式存在。我们使用独特的基于氟化阻挡层的光刻技术制造了横向有机 p-n 结，从而首次能够在对有机 p-n 界面处的电势进行观察的同时进行电荷输运测量。我们发现，该器件的二极管特性（电流输出和整流比）与结附近表面电势的变化一致，并且电流-电压曲线和结电势可通过第三个栅电极强烈且自洽地进行调制。我们的技术具有通用性，这使其成为研究有机半导体结物理性质的一种有吸引力的方法。光刻技术适用于各种软材料图案。内置电势的观察在有机结与教科书中无机器件描述之间建立了重要联系。最后，这些类型的电势可能会被证明是控制有机光伏器件中电荷分离效率的因素。
