Nanoscale Charge Transport and Internal Structure of Bulk Heterojunction Conjugated Polymer/Fullerene Solar Cells by Scanning Probe Microscopy

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• 作者：Mark Dante ; Jeffrey Peet ; Thuc-Quyen Nguyen
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：May 8, 2008
• 年：2008
• 卷：112
• 期：18
• 页码：7241 - 7249
• 全文大小：1214K
• 年卷期：v.112,no.18(May 8, 2008)
• ISSN：1932-7455

文摘

Tapping mode atomic force microscopy (AFM) was used to probe the surface and internal structures of bulkheterojunction poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) films.AFM images obtained from the surface of the P3HT:PCBM film and from the cross section reveal for thefirst time the nanoscale three-dimensional P3HT and PCBM networks. Two different measurement modes ofconducting atomic force microscopy (C-AFM) were used to study the nanoscale charge transport in P3HT:PCBM films. In C-AFM, the local current map at a constant bias and the surface topography are obtainedsimultaneously. Hole and electron current images can be used to determine the composition of the phasesegregation domains. Alternatively, local current-voltage curves can be measured that can be used to calculatecharge carrier mobilities. Hole current images and mobilities were obtained using Pt-coated silicon probes,whereas Mg-coated silicon probes were used to measure nanoscale electron mobilities. Variations in electricalproperties and surface topography were examined. Comparison against films of neat P3HT shows that blendingP3HT with PCBM decreases the polymer hole mobility. In all cases, nanoscale hole and electron mobilitiesincrease upon annealing, consistent with increased internal order. A direct correlation between the C-AFM-determined nanoscale properties and solar cell power conversion efficiencies is observed.