MPN is grateful to the Director's Fellowship Program for financial support. MPN wants to thank Yu-Chih Tseng for help with development of the protocol for solar cell processing. This work was performed at the Center for Nanoscale Materials, a U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences User Facility under Contract No. DE-AC02-06CH11357.

1. Signal Acquisition
<ol class="lalpha">
 <li>Install sample (polymer solar cell without cathode (ITO/PEDOT:PSS/P3HT:PC61BM)) into a commercial Multimode AFM (Veeco, Santa Barbara, CA) equipped with Nanoscope-V controller.</li>
 <li>Install conductive AFM probe into Multimode AFM probe holder.</li>
 <li>Create electrical connection between the AFM probe, sample and voltage source.</li>
 <li>Route current amplifier output (current signal), Multimode AFM deflection output (force signal), Multimode AFM sample ...

<ol>
	<li>Chen, W., Nikiforov, M. P., Darling, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphology+characterization+in+organic+and+hybrid+solar+cells.">Morphology characterization in organic and hybrid solar cells.</a> Energy Environ. Sci. , (2012).</li><li>Dupont, S. R., Oliver, M., Krebs, F. C., Dauskardt, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interlayer+adhesion+in+roll-to-roll+processed+flexible+inverted+polymer+solar+cells.">Interlayer adhesion in roll-to-roll processed flexible inverted polymer solar cells.</a> Sol. Energy. 97, 171-175 (2012).</li><li>Green, M. A., Emery, K., Hishikawa, Y., Warta, W., Dunlop, E. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solar+cell+efficiency+tables+(version+39).">Solar cell efficiency tables (version 39).</a> Progress in Photovoltaics. 20 (1), 12-20 (2012).</li><li>Krebs, F. C., Gevorgyan, S. A., Alstrup, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+roll-to-roll+process+to+flexible+polymer+solar+cells:+model+studies,+manufacture+and+operational+stability+studies.">A roll-to-roll process to flexible polymer solar cells: model studies, manufacture and operational stability studies.</a> Journal of Materials Chemistry. 19 (30), 5442-5451 (2009).</li><li>Binnig, G., Quate, C. F., Gerber, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atomic+Force+Microscope.">Atomic Force Microscope.</a> Physical Review Letters. 56 (9), 930-933 (1986).</li><li>Hurley, D. C., Kopycinska-Muller, M., Kos, A. B., Geiss, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoscale+elastic-property+measurements+and+mapping+using+atomic+force+acoustic+microscopy+methods.">Nanoscale elastic-property measurements and mapping using atomic force acoustic microscopy methods.</a> Measurement Science &amp; Technology. 16 (11), 2167-2172 (2005).</li><li>Jesse, S., Nikiforov, M. P., Germinario, L. T., Kalinin, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+thermomechanical+characterization+of+phase+transitions+using+band+excitation+atomic+force+acoustic+microscopy+with+heated+probe.">Local thermomechanical characterization of phase transitions using band excitation atomic force acoustic microscopy with heated probe.</a> Applied Physics Letters. 93 (7), (2008).</li><li>Nikiforov, M. P., Gam, S., Jesse, S., Composto, R. J., Kalinin, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphology+Mapping+of+Phase-Separated+Polymer+Films+Using+Nanothermal+Analysis.">Morphology Mapping of Phase-Separated Polymer Films Using Nanothermal Analysis.</a> Macromolecules. 43 (16), 6724-6730 (2010).</li><li>Nikiforov, M. P., Jesse, S., Morozovska, A. N., Eliseev, E. A., Germinario, L. T., Kalinin, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+the+temperature+dependence+of+the+mechanical+properties+of+polymers+at+the+nanoscale+with+band+excitation+thermal+scanning+probe+microscopy.">Probing the temperature dependence of the mechanical properties of polymers at the nanoscale with band excitation thermal scanning probe microscopy.</a> Nanotechnology. 20 (39), (2009).</li><li>Rabe, U., Amelio, S., Kopycinska, M., Hirsekorn, S., Kempf, M., Goken, M., Arnold, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+and+measurement+of+local+mechanical+material+properties+by+atomic+force+acoustic+microscopy.">Imaging and measurement of local mechanical material properties by atomic force acoustic microscopy.</a> Surface and Interface Analysis. 33 (2), 65-70 (2002).</li><li>Nikiforov, M. P., Zerweck, U., Milde, P., Loppacher, C., Park, T. -. H., Uyeda, H. T., Therien, M. J., Eng, L., Bonnell, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+molecular+orientation+on+the+potential+of+porphyrin-metal+contacts.">The effect of molecular orientation on the potential of porphyrin-metal contacts.</a> Nano Letters. 8 (1), 110-113 (2008).</li><li>Nikiforov, M. N., Brukman, M. J., Bonnell, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+characterization+of+defects+in+oxide+thin+films.">High-resolution characterization of defects in oxide thin films.</a> Applied Physics Letters. 93 (18), (2008).</li><li>Kalinin, S. V., Karapetian, E., Kachanov, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoelectromechanics+of+piezoresponse+force+microscopy.">Nanoelectromechanics of piezoresponse force microscopy.</a> Physical Review B. 70 (18), (2004).</li><li>Kolosov, O., Gruverman, A., Hatano, J., Takahashi, K., Tokumoto, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoscale+Visualization+and+Control+of+Ferroelectric+Domains+by+Atomic-Force+Microscopy.">Nanoscale Visualization and Control of Ferroelectric Domains by Atomic-Force Microscopy.</a> Physical Review Letters. 74 (21), 4309-4312 (1995).</li><li>Nikiforov, M. P., Thompson, G. L., Reukov, V. V., Jesse, S., Guo, S., Rodriguez, B. J., Seal, K., Vertegel, A. A., Kalinin, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Double-Layer+Mediated+Electromechanical+Response+of+Amyloid+Fibrils+in+Liquid+Environment.">Double-Layer Mediated Electromechanical Response of Amyloid Fibrils in Liquid Environment.</a> Acs Nano. 4 (2), 689-698 (2010).</li><li>Botiz, I., Darling, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optoelectronics+using+block+copolymers.">Optoelectronics using block copolymers.</a> Materials Today. 13 (5), 42-51 (2010).</li><li>Brabec, C. J., Heeney, M., McCulloch, I., Nelson, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+blend+microstructure+on+bulk+heterojunction+organic+photovoltaic+performance.">Influence of blend microstructure on bulk heterojunction organic photovoltaic performance.</a> Chemical Society Reviews. 40 (3), 1185-1199 (2011).</li><li>Karagiannidis, P. G., Kassavetis, S., Pitsalidis, C., Logothetidis, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+annealing+effect+on+the+nanomechanical+properties+and+structure+of+P3HT:+PCBM+thin+films.">Thermal annealing effect on the nanomechanical properties and structure of P3HT: PCBM thin films.</a> Thin Solid Films. 519 (12), 4105-4109 (2011).</li><li>Sweers, K., vander Werf, K., Bennink, M., Subramaniam, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanomechanical+properties+of+alpha-synuclein+amyloid+fibrils:+a+comparative+study+by+nanoindentation,+harmonic+force+microscopy,+and+Peakforce+QNM.">Nanomechanical properties of alpha-synuclein amyloid fibrils: a comparative study by nanoindentation, harmonic force microscopy, and Peakforce QNM.</a> Nanoscale Research Letters. 6, (2011).</li><li>Nikiforov, M. P., Darling, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+conductive+atomic+force+microscopy+measurements+on+organic+photovoltaic+materials+via+mitigation+of+contact+area+uncertainty.">Improved conductive atomic force microscopy measurements on organic photovoltaic materials via mitigation of contact area uncertainty.</a> Progress in Photovoltaics: Research and Applications. , (2012).</li><li>Li, H. -. C., Rao, K. K., Jeng, J. -. Y., Hsiao, Y. -. J., Guo, T. -. F., Jeng, Y. -. R., Wen, T. -. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nano-scale+mechanical+properties+of+polymer/fullerene+bulk+hetero-junction+films+and+their+influence+on+photovoltaic+cells.">Nano-scale mechanical properties of polymer/fullerene bulk hetero-junction films and their influence on photovoltaic cells.</a> Solar Energy Materials and Solar Cells. 95 (11), 2976-2980 (2011).</li><li>Mueller, C., Goffri, S., Breiby, D. W., Andreasen, J. W., Chanzy, H. D., Janssen, R. A. J., Nielsen, M. M., Radano, C. P., Sirringhaus, H., Smith, P., Stingelin-Stutzmann, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tough,+semiconducting+polyethylene-poly(3-hexylthiophene)+diblock+copolymers.">Tough, semiconducting polyethylene-poly(3-hexylthiophene) diblock copolymers.</a> Advanced Functional Materials. 17 (15), 2674-2679 (2007).</li><li>Kuila, B. K., Nandi, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physical,+mechanical,+and+conductivity+properties+of+poly(3-hexylthiophene)-montmorillonite+clay+nanocomposites+produced+by+the+solvent+casting+method.">Physical, mechanical, and conductivity properties of poly(3-hexylthiophene)-montmorillonite clay nanocomposites produced by the solvent casting method.</a> Macromolecules. 37 (23), 8577-8584 (2004).</li><li>O'Connor, B., Chan, E. P., Chan, C., Conrad, B. R., Richter, L. J., Kline, R. J., Heeney, M., McCulloch, I., Soles, C. L., DeLongchamp, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlations+between+Mechanical+and+Electrical+Properties+of+Polythiophenes.">Correlations between Mechanical and Electrical Properties of Polythiophenes.</a> Acs Nano. 4 (12), 7538-7544 (2010).</li><li>Tahk, D., Lee, H. H., Khang, D. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elastic+Moduli+of+Organic+Electronic+Materials+by+the+Buckling+Method.">Elastic Moduli of Organic Electronic Materials by the Buckling Method.</a> Macromolecules. 42 (18), 7079-7083 (2009).</li><li>Kuila, B. K., Nandi, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+hierarchy+in+melt-processed+poly(3-hexyl+thiophene)-montmorillonite+clay+nanocomposites:+Novel+physical,+mechanical,+optical,+and+conductivity+properties.">Structural hierarchy in melt-processed poly(3-hexyl thiophene)-montmorillonite clay nanocomposites: Novel physical, mechanical, optical, and conductivity properties.</a> Journal of Physical Chemistry B. 110 (4), 1621-1631 (2006).</li><li>Nikiforov, M. P., Darling, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+conductive+atomic+force+microscopy+measurements+on+organic+photovoltaic+materials+via+mitigation+of+contact+area+uncertainty.">Improved conductive atomic force microscopy measurements on organic photovoltaic materials via mitigation of contact area uncertainty.</a> Progress in Photovoltaics: Research and Applications. , (2012).</li><li>Kim, J. Y., Frisbie, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+of+Phase+Behavior+and+Charge+Transport+in+Conjugated+Polymer/Fullerene+Blends.">Correlation of Phase Behavior and Charge Transport in Conjugated Polymer/Fullerene Blends.</a> Journal of Physical Chemistry C. 112 (45), 17726-17736 (2008).</li><li>Bange, S., Kuksov, A., Neher, D., Vollmer, A., Koch, N., Ludemann, A., Heun, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+poly(3,4-ethylenedioxythiophene):poly(styrenesulphonate)+as+a+hole+injection+layer+in+a+blue-emitting+polymer+light-emitting+diode.">The role of poly(3,4-ethylenedioxythiophene):poly(styrenesulphonate) as a hole injection layer in a blue-emitting polymer light-emitting diode.</a> Journal of Applied Physics. 104 (10), (2008).</li></ol>

Recent breakthroughs in power conversion efficiency (PCE) of organic photovoltaic (OPV) cells (pushing 10% at the cell level)3 in concert with compliance with high-throughput and low-cost manufacturing processes4 have brought a spotlight onto OPV technology as a possible solution for the challenge of inexpensive manufacturing of large-area solar cells. OPV materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials and performance of photovoltaic devices are intimately connected. Thus, understanding inhomogeneity in composition as well as electrical properties of OPV materials is of paramount importance for moving OPV technology forward. Atomic force microscopy (AFM) has been developed as a tool for high-resolution measurements of surface topography since 1986.5 Nowadays, techniques for materials properties (Young's modulus,6-10 work function,11 conductivity,12 electromechanics,13-15 etc.) measurements are attracting increasing attention. In the case of OPV materials, correlation of local phase composition and electrical properties holds promise for revealing better understanding of the inner workings of organic solar cells.1, 16-17 AFM-based techniques are capable of high-resolution phase attribution8 as well as electrical properties mapping in polymeric materials. Thus, in principle, correlation of polymer phase composition (through mechanical measurements)18 and electrical properties is possible using AFM-based techniques. Many AFM-based techniques for measurements of mechanical and electrical properties of materials use the assumption of constant area of contact between the AFM probe and the surface. This assumption often fails, which results in strong correlation among surface topography and mechanical/electrical properties. Recently, a new AFM-based technique for high-throughput measurements of mechanical properties (PeakForce)19 was introduced. PeakForce TUNA (variation of the PeakForce method) provides a platform for concurrent measurements of mechanical and electrical properties of the sample. However, the PeakForce TUNA method produces mechanical and electrical property maps, which usually are strongly correlated because of unaccounted variability of contact during measurements. In this paper, we present an experimental protocol for removing correlations associated with varying contact radius while maintaining accurate measurements of the mechanical and electrical properties using AFM. Implementation of the protocol results in quantitative measurements of materials' resistance and Young's Modulus.

<table border="1">
 <tbody>
 <tr>
 <td>Name of Reagent/Material</td>
 <td>Company</td>
 <td>Catalog Number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>Plextronics inks</td>
 <td>Plexcore </td>
 <td>PV 1000</td>
 <td></td>
 </tr>
 <tr>
 <td>ITO-coated glass substrates</td>
 <td>Delta Technologies, Inc</td>
 <td></td>
 <td>25 Ohms/sq</td>
 </tr>
 <tr>
 <td>30 MHz synthesized function generator</td>
 <td>Stanfor Research Systems</td>
 <td>DS345</td>
 <td></td>
 </tr>
 <tr>
 <td>Current amplifier</td>
 <td>Femto</td>
 <td>DLPCA-200</td>
 <td></td>
 </tr>
 <tr>
 <td>Multimode AFM</td>
 <td>Veeco, Santa Barbara, CA</td>
 <td></td>
 <td>equipped with Nanoscope-V controller</td>
 </tr>
 <tr>
 <td>DAQ card</td>
 <td>National Instruments</td>
 <td>NI-PCI-6115</td>
 <td></td>
 </tr>
 <tr>
 <td>Metal Pt probes</td>
 <td>RMNano</td>
 <td>12Pt3008</td>
 <td></td>
 </tr>
 <tr>
 <td>MATLAB software</td>
 <td>Mathworks</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>LabView software</td>
 <td>National Instruments</td>
 <td></td>
 <td></td>
 </tr>
 </tbody>
</table>

concurrent quantitative conductivity and mechanical properties measurements of organic photovoltaic materials using afm

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. Thus, understanding of spatial variations in composition as well as electrical properties of OPV materials is of paramount importance for moving PV technology forward.1,2 In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution. Currently, materials properties measurements performed using commercially available AFM-based techniques (PeakForce, conductive AFM) generally provide only qualitative information. The values for resistance as well as Young's modulus measured using our method on the prototypical ITO/PEDOT:PSS/P3HT:PC61BM system correspond well with literature data. The P3HT:PC61BM blend separates onto PC61BM-rich and P3HT-rich domains. Mechanical properties of PC61BM-rich and P3HT-rich domains are different, which allows for domain attribution on the surface of the film. Importantly, combining mechanical and electrical data allows for correlation of the domain structure on the surface of the film with electrical properties variation measured through the thickness of the film.

Young's modulus and resistivity maps (Figure 3) present typical results of the measurements described above. Mechanical and electrical properties of the ITO/PEDOT:PSS/P3HT:PC61BM stack were measured at negative (-10 V) and positive (+6 V) voltages applied to the AFM probe. Imaging artifacts, associated with electrostatic interaction between the AFM probe and the sample, are a common problem for quantitative measurements of functional properties using AFM. The similarity of Young's modul...

Watch this Scientific Journal Video about Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM at JoVE.com

Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution.

Organic photovoltaic  (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale  inhomogeneity of OPV materials affects performance ...

concurrent-quantitative-conductivity-mechanical-properties

Research

JoVE Journal

Engineering

11.6K vistas.  Argonne National Laboratory. Fotovoltaicos orgánicos (OPV) materiales son inherentemente no homogénea a escala nanométrica. Falta de homogeneidad de escala nanométrica de materiales OPV afecta al rendimiento de los dispositivos fotovoltaicos. En este trabajo se describe un protocolo para las mediciones cuantitativas de las propiedades eléctricas y mecánicas de los materiales de la OPV con resolución sub-100 nm.