Name: using neutron spin echo resolved grazing incidence scattering to investigate organic solar cell materials
Uploaded: 2014-01-15T13:00:00
Description: Watch this Scientific Journal Video about Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials at JoVE.com

AJP was funded by the EPSRC Soft Nanotechnology platform grant EP/E046215/1. The neutron experiments were supported by the STFC via the allocation of experimental time to use OffSpec (RB 1110285).

1. Sample Preparation
<ol>
	<li>Clean the silicon substrates by placing 2 in&#160;silicon wafers that are 4 mm thick in oxygen plasma for 10 min.</li>
	<li>Spincoat the first layer on the substrates
	<ol>
		<li>Filter the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) through a 0.45 &#181;m PTFE filter (PALL).</li>
		<li>Use approximately 0.5 ml for each sample to spin coat a PEDOT:PSS thin film onto the two clean substrates at 5,000 rpm spinning for 60 sec.</li>
		<li>Dry each substrate for 10 mi...

<ol>
	<li>Mezei, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutron+spin+echo:+A+new+concept+in+polarized+thermal+neutron+techniques.">Neutron spin echo: A new concept in polarized thermal neutron techniques.</a> Zeitschriftf&#252;r Physik A Hadrons Nuclei. 255, 146-160 (1972).</li><li>Falus, P., Vorobiev, A., Krist, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Test+of+a+two-dimensional+neutron+spin+analyzer.">Test of a two-dimensional neutron spin analyzer.</a> Physica B Condens. Matter. Mater. Phys. , 385-386 (2006).</li><li>Ashkar, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamical+theory+calculations+of+spin-echo+resolved+grazing-incidence+scattering+from+a+diffraction+grating.">Dynamical theory calculations of spin-echo resolved grazing-incidence scattering from a diffraction grating.</a> J. Appl. Crystallogr. 43 (3), 455-465 (2010).</li><li>Ashkar, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamical+theory:+Application+to+spin-echo+resolved+grazing+incidence+scattering+from+periodic+structures.">Dynamical theory: Application to spin-echo resolved grazing incidence scattering from periodic structures.</a> J. Appl. Phys. 110 (10), (2011).</li><li>Pynn, R., Ashkar, R., Stonaha, P., Washington, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A.L.,Some+recent+results+using+spin+echo+resolved+grazing+incidence+scattering.">A.L.,Some recent results using spin echo resolved grazing incidence scattering.</a> SERGIS). hysica B Condens. Matter. Mater. Phys. 406 (12), 2350-2353 (2011).</li><li>Ashkar, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spin-Echo+Resolved+Grazing+Incidence+Scattering+(SERGIS)+at+Pulsed+and+CW+Neutron+Sources.">Spin-Echo Resolved Grazing Incidence Scattering (SERGIS) at Pulsed and CW Neutron Sources.</a> J. Phy. Conf. Ser. 251 (1), (2010).</li><li>Vorobiev, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase+and+microphase+separation+of+polymer+thin+films+dewetted+from+Silicon-A+spin-echo+resolved+grazing+incidence+neutron+scattering+study.">Phase and microphase separation of polymer thin films dewetted from Silicon-A spin-echo resolved grazing incidence neutron scattering study.</a> J. Phys. Chem. B. 115 (19), 5754-5765 (2011).</li><li>Major, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+spin-echo+resolved+grazing+incidence+scattering+setup+for+the+neutron+interrogation+of+buried+nanostructures.">A spin-echo resolved grazing incidence scattering setup for the neutron interrogation of buried nanostructures.</a> Rev. Sci. Instrum. 80 (12), (2009).</li><li>Parnell, A. J., Dalgliesh, R. M., Jones, R. A. L., Dunbar, A. D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+neutron+spin+echo+resolved+grazing+incidence+scattering+study+of+crystallites+in+organic+photovoltaic+thin+films.">A neutron spin echo resolved grazing incidence scattering study of crystallites in organic photovoltaic thin films.</a> Appl. Phys. Lett. 102, (2013).</li><li>Dalgliesh, R. M., Langridge, S., Plomp, J., De Haan, V. O., Van Well, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Offspec,+the+ISIS+spin-echo+reflectometer.+hysica+B+Condens..">Offspec, the ISIS spin-echo reflectometer. hysica B Condens..</a> Matter. Mater. Phys. 406 (12), 2346-2349 (2011).</li><li>Krouglov, T., de Schepper, I. M., Bouwman, W. G., Rekveldt, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-space+interpretation+of+spin-echo+small-angle+neutron+scattering.">Real-space interpretation of spin-echo small-angle neutron scattering.</a> J. Appl. Crystallogr. 36, 117-124 (2003).</li><li>Brady, M. A., Su, G. M., Chabinyc, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+progress+in+the+morphology+of+bulk+heterojunctionphotovoltaics.">Recent progress in the morphology of bulk heterojunctionphotovoltaics.</a> Soft Matter. 7 (23), 11065-11077 (2011).</li><li>Huang, Y. -. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+the+effect+of+annealing+process+on+the+performance+of+P3HT/PCBM+photovoltaic+devices+using+scanning-probe+microscopy..">Study of the effect of annealing process on the performance of P3HT/PCBM photovoltaic devices using scanning-probe microscopy..</a> Solar Energy Mater. Solar Cells. 93 (6-7), 888-892 (2009).</li><li>Parnell, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Depletion+of+PCBM+at+the+Cathode+Interface+in+P3HT/PCBM+Thin+Films+as+Quantified+via+Neutron+Reflectivity+Measurements.">Depletion of PCBM at the Cathode Interface in P3HT/PCBM Thin Films as Quantified via Neutron Reflectivity Measurements.</a> Adv. Mater. 22 (22), 2444-2447 (2010).</li></ol>

The microscopy data in Figure 1 clearly shows that before annealing the P3HT:PCBM thin film is flat and smooth and after thermal annealing there are many large irregular PCBM crystallites present on the surface with lateral dimensions ranging between about 1-10 &#181;m. This is attributed to PCBM migration towards the top surface of the film and subsequent aggregation to form large crystallites. A strong SERGIS signal associated with scattering from PCBM crystallites in the annealed sample is seen in <st...

The SERGIS technique aims to be able to yield unique structural information not accessible using other scattering or microscopy techniques from thin film samples. Microscopy techniques are typically surface limited or require significant alteration/sample preparation to view internal structures. Conventional scattering techniques such as reflectivity can provide detailed information about buried sample structures as a function of depth within the thin film but cannot probe structure in the plane of the thin film easily. Ultimately it is hoped that SERGIS will enable this lateral structure to be probed even when buried within the thin film sample. The representative results presented here demonstrate that it is possible to observe a SERGIS signal from irregular sample features and that the measured signal can be correlated with a characteristic length scale associated with the features present in the sample, as confirmed by conventional microscopy techniques.
Inelastic spin echo techniques were developed by Mezei&#160;et al.1&#160;in the 1970s. Since then the SERGIS technique (which is an extension of the ideas of Mezei&#160;et al.) has been successfully demonstrated experimentally using a variety of samples such as highly regular diffraction gratings2-6 and circular de-wetted polymer droplets7. A dynamical theory has been developed by Pynn and coworkers to model the strong scattering from highly regular samples3-6,8. This work has highlighted many practical aspects to be considered when performing this type of measurement and has led to a constant dialogue within a small multinational community.
Good results from SERGIS experiments will most likely be obtained if the sample being measured consists of a thin film on a flat substrate and contains scattering features with a high density of moderately sized features (30 nm to 5 &#181;m) that scatter neutrons strongly, as demonstrated by the authors9. Unlike other established reflectivity techniques that probe the sample as a function of depth, the SERGIS technique has the advantage that it can probe structures in the plane of the sample surface. Furthermore, the use of spin-echo removes the requirement to tightly collimate the neutron beam in order to obtain either high spatial or energy resolution, consequently significant flux gains can be achieved. This is particularly relevant for grazing incidence geometries that are significantly flux limited because of the need to collimate the beam strongly in one direction. Using the OffSpec instrument it should therefore be possible to probe length scales from 30 nm to 5 &#181;m in both bulk and surface structures.

<table border="0" cellpadding="0" cellspacing="0" width="605">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Silicon 2 in silicon substrates</td>
			<td style="width:103px;">Prolog</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">4 mm thick polished one side</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Oxygen plasma</td>
			<td style="width:103px;">Diener</td>
			<td style="width:119px;"></td>
			<td>Oxygen plasma cleaning system to clean substrates prior to coating</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)</td>
			<td style="width:103px;">Ossila</td>
			<td style="width:119px;"></td>
			<td>PEDOT:PSS conductive polymer layer for organic photovoltaic samples</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.45 &#956;m PTFE filter</td>
			<td style="width:103px;">Sigma Aldrich</td>
			<td style="width:119px;"></td>
			<td>Filer to remove aggregates from PEDOT:PSS and P3HT solutions</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chlorobenzene</td>
			<td style="width:103px;">Sigma Aldrich</td>
			<td style="width:119px;"></td>
			<td>Solvent for P3HT</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Poly(3-hexylthiophene-2,5-diyl)</td>
			<td style="width:103px;">Ossila</td>
			<td style="width:119px;"></td>
			<td>P3HT - polymer used in polymer photovoltaics</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Spin Coater</td>
			<td style="width:103px;">Laurell</td>
			<td style="width:119px;"></td>
			<td>Deposition system for making flat thin polymer films</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Vacuum Oven</td>
			<td style="width:103px;">Binder</td>
			<td style="width:119px;"></td>
			<td>Oven fro annealing samples after preparation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nikon Eclipse E600 optical microscope</td>
			<td style="width:103px;">Nikon</td>
			<td style="width:119px;"></td>
			<td>Microscope</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Veeco Dimension 3100 AFM</td>
			<td style="width:103px;">Veeco</td>
			<td style="width:119px;"></td>
			<td>AFM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tapping mode tips (~275 kHz)</td>
			<td style="width:103px;">Olympus</td>
			<td style="width:119px;"></td>
			<td>AFM tips</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Quartz Disc</td>
			<td style="width:103px;"></td>
			<td style="width:119px;"></td>
			<td>Refrence samples for SERGIS measurement</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Spin Echo off-specular reflectometer</td>
			<td colspan="2">OffSpec at the ISIS Pulsed Neutron and Muon Source (Oxfordshire, UK)</td>
			<td>Produces pulsed neutrons 2-14 &#197;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Neutron Detector</td>
			<td style="width:103px;">Offspec</td>
			<td style="width:119px;"></td>
			<td>vertically oriented linear scintillator detector</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RF spin flippers</td>
			<td style="width:103px;">Offspec</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Magnetic Field Guides</td>
			<td style="width:103px;">Offspec</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Data Manipulation Software</td>
			<td style="width:103px;">Mantid</td>
			<td style="width:119px;"></td>
			<td><a href="http://www.mantidproject.org/Main_Page">http://www.mantidproject.org/Main_Page</a></td>
		</tr>
	</tbody>
</table>

using neutron spin echo resolved grazing incidence scattering to investigate organic solar cell materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

The representative results from samples of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly(3-hexylthiophene-2,5-diyl) (P3HT) presented here are of significant interest because of their widespread application as bulk hetero-junction materials in organic photovoltaic cells12,13. Typically during the fabrication of an organic photovoltaic device, a P3HT:PCBM blend solution is spin-cast from a blend solution to form a thin film on a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coa...

Watch this Scientific Journal Video about Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials at JoVE.com

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

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