Direct Observation of CdCl2 Treatment Induced Grain Boundary Carrier Depletion in CdTe Solar Cells Using Scanning Probe Microwave Reflectivity Based Capacitance Measurements

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• 作者：Mohit Tuteja ; Prakash Koirala ; Vasilios Palekis ; Scott MacLaren ; Chris S. Ferekides ; Robert W. Collins ; Angus A. Rockett
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：April 7, 2016
• 年：2016
• 卷：120
• 期：13
• 页码：7020-7024
• 全文大小：329K
• ISSN：1932-7455

文摘

Device grade polycrystalline CdTe films, grown by rf-sputtering (yielding up to 13% efficient devices) and close-spaced sublimation (CSS) (yielding up to 16% efficient devices), have been analyzed using scanning microwave impedance microscopy (sMIM). In order to study the effect of Cl on the electronic properties of grain boundaries in CdTe, sMIM based capacitance measurements were performed on the surfaces of as-deposited and CdCl₂ annealed CdTe films. The measurements were performed with an sMIM instrument operating at ∼3 GHz probe signal frequency in conjunction with a combination of ac and dc voltage biases applied to the tip. It was found that CdCl₂ annealed CdTe samples deposited using both CSS and sputtering exhibit carrier depletion along the grain boundaries as compared to the grain bulk. The grain boundary carrier depletion was not observed in samples that have not been CdCl₂ annealed and hence have no incorporated Cl.