Support for this work was provided by DOE STTR grant DE-SC0003664 on Parallel Tandem Organic Solar Cells with Carbon Nanotube Sheet Interlayers and Welch Foundation grant AT-1617. The authors thank J. Bykova for providing CNT forests and A. R. Howard, K. Meilczarek, and J. Velten for technical assistance and useful discussions.

1. óxido de estaño e indio (ITO) Patrones y limpieza NOTA: El uso 15Ω / □ vidrio ITO, y compra o cortar el vidrio ITO en tamaños adecuados para el recubrimiento por rotación y la fotolitografía. Es más eficiente para realizar los pasos 1.1 a 1.7 en un pedazo de vidrio tan grande como sea posible, y luego se corta en dispositivos más pequeños. También tenga en cuenta que los pasos 1.1 a 1.7 requieren el vidrio ITO a orientarse con el ITO-hacia arriba. Esto se puede comprobar fácilmente con el ajuste de la resistencia de un multímetro. <ol><li> Capa de la vuelta 1 ml de S1813 fotorresistente positivo en el lado ITO-del vidrio ITO a una velocidad de 3.000 rpm durante 1 min. Usar más para resistir grandes piezas de vidrio, asegúrese de que todo el vidrio está recubierta, y eliminar todas las burbujas antes de comenzar el revestidor de giro. </li><li> Recocer el vidrio revestido resistir, en una placa caliente, a 115 ° C durante 1 min. </li><li> Cargar la muestra y la fotomáscara sobre el alineador de contacto. </li><li> Exponga el vidrio ITO fotoprotector recubierto por una aprotiempo proceda. El tiempo de exposición es de alrededor de 10 segundos, pero este tiempo puede variar en base a la intensidad de la lámpara UV, el tipo de resina fotosensible, y grosor. </li><li> Desarrollar los sustratos UV-expuesta en desarrollador MF311. Proceso automatizado de un procesador de giro produce los mejores y más resultados repetibles, pero el desarrollo se puede hacer manualmente como sigue. <ol><li> Sumergir los sustratos expuestas a UV durante 1 min en el revelador, seguido de un enjuague en agua desionizada (DI) de agua y de secar con una pistola de nitrógeno. Debido a que el desarrollador pierde fuerza rápidamente, sustituya el revelador entre las muestras, o, alternativamente, aumentar el tiempo de desarrollo al reutilizar desarrollador. </li></ol></li><li> Etch los sustratos de ITO en ácido clorhídrico concentrado (HCl). Esto tarda entre 5-10 min dependiendo de la concentración del HCl. Enjuague en agua DI, seco, y poner a prueba la resistencia de las partes grabadas con un multímetro. Si cualquiera de conductividad permanece, grabar durante un tiempo más largo. </li><li> Una vez que el grabado, retire la photoresist con acetona. Tenga en cuenta que la pronta eliminación de la fotoprotección impide HCl residual de sobre-grabado de la OIC con dibujos. </li><li> Si es necesario, cortar los grabados sustratos de vidrio ITO en tamaños de los dispositivos. </li><li> Limpiar los sustratos de ITO en un ultrasonicador baño en una secuencia de disolventes - agua DI, acetona, tolueno, metanol, y, finalmente, alcohol isopropílico. </li></ol> 2. OPV Fabricación de células Sub <ol><li> Preparar P3HT: PC 61 BM solución. NOTA: Para obtener los resultados más consistentes, preparar las soluciones en un ambiente de nitrógeno. Es posible seguir este procedimiento en las condiciones ambientales. <ol><li> Encuentre y anote la masa de dos limpias, ~ 4 ml frasco de vidrio y sus tapas, y marcarlos con un marcador permanente para distinguirlos de los otros. </li><li> En una caja de guantes de nitrógeno o argón, transferir aproximadamente 10 mg de poli (3-hexiltiofeno-2,5-diilo) (P3HT) a un vial y aproximadamente 10 mg de fenil-C 61 éster metílico del ácido butírico (PC 61 BM) a la otra. </li><li> Pesar los viales otra vez para encontrar la masa de la P3HT y PC 61 BM. </li><li> La transferencia de los viales con P3HT y PC 61 BM en una caja de guantes para el resto del proceso de toma de solución. </li><li> Añadir una barra de agitación magnética en cada vial y luego agregue suficiente clorobenceno a cada uno para crear soluciones de 45 mg / ml. </li><li> Colocar las soluciones sobre una placa de agitación magnética caliente a 55 ° C durante aproximadamente 2 horas o hasta que los solutos se han disuelto completamente. </li><li> Mezclar volúmenes iguales de la P3HT y PC 61 BM soluciones juntos, y dejar que la solución mixta de agitación durante otra hora antes de su uso. </li></ol></li><li> Preparar PTB7: PC 71 BM solución. <ol><li> Repita los pasos 2.1.1 al 2.1.4 con poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) y 7,1-fenil-butírico éster metílico del ácido (PC 71 BM) en lugar de P3HT y PC61 BM. </li><li> Haga una mezcla de 3% en volumen 1,8-diiodooctane (DIO) en clorobenceno. Esta mezcla se llama DIO-CB. </li><li> Añadir una barra de agitación magnética en cada vial y luego añadir una cantidad suficiente DIO-CB al vial PTB7 tener una solución de 12 mg / ml y lo suficientemente DIO-CB a la PC 71 BM vial tener una solución 40 mg / ml. </li><li> Deja que estas soluciones revuelven en un plato caliente a 70 ° C durante dos días. </li><li> Mezclar las soluciones en una relación en peso de PTB7 a PC 71 BM de 1 a 1,5. </li><li> Deje que la solución mixta de agitación durante otra hora a 70 ° C antes de su uso. </li></ol></li><li> Filtro de poli (3,4-etilendioxitiofeno): poli- (estirenosulfonato) (PEDOT: PSS) a través de un filtro de nylon de tamaño de poro 0,45 micras. Tenga en cuenta este procedimiento utiliza P VP AI4083. </li><li> Girar Coat capas activas. <ol><li> Coloque sustratos ITO limpiados, ITO-hacia arriba, en un limpiador UV-ozono durante 5 min. </li><li> Spin-abrigo de 120 l de la PEDOT: PSS se filtraron a los rayos UV tratada con ozono, modelado ITO- sustrato de vidrios a 3.000 rpm durante 1 min. Esto debería producir una capa gruesa 30 nm. </li><li> Recocer el PEDOT: PSS sustratos recubiertos de ITO durante 5 min a 180 ° C. </li><li> Spin-abrigo de 70 l de la P3HT mixta: PC 61 BM solución sobre PEDOT: PSS recubierto ITO sustratos a aproximadamente 1.000 rpm durante 1 min. Variar la velocidad según sea necesario para depositar una capa activa nm de espesor 200. </li><li> Recocer el P3HT: sustratos PC 61 BM recubierto a 170 ° C durante 5 min. Los resultados pueden variar de la temperatura óptima de recocido. </li><li> Spin-abrigo de 70 l de la PTB7 mixta: PC 71 BM solución sobre PEDOT: PSS recubierto ITO sustratos a aproximadamente 700 rpm durante 1 min. Variar la velocidad según sea necesario para depositar una capa activa 100 nm de espesor. </li><li> Cargue el PTB7: PC 71 BM sustratos recubiertos en un alto vacío (&lt;2 x 10 -6 Torr) para eliminar la cámara de DIO residual. Por lo general, dejar las muestras en la cámara de O / N. </li></ol></li></ol> 3. Fabrique el dispositivo Tandem &lt;ol&gt; <li> Electrodos Laminado CNT. <ol><li> Cortar los sustratos PTB7 y P3HT por la mitad para hacer un dispositivo tándem. Un patrón de ITO especializada no requeriría este paso. El patrón de ITO debe tener al menos dos electrodos ITO paralelo que se extiende desde un borde a un mm de distancia de la otra. </li><li> En primer lugar preparar el PTB7 y sustratos recubiertos por P3HT secándose polímero y PEDOT a partir de los bordes del vidrio, y exponer la tira de ITO que se utiliza como electrodo común como se ve en el primer panel de la Figura 1. </li><li> Laminar el electrodo común CNT en la parte superior de los electrodos PTB7 y P3HT. Aplique una capa SWCNT colocando el lado de la CNT del papel de filtro en el dispositivo, presionando suavemente, y luego pelar el papel de filtro de distancia. Esto se muestra en el segundo panel de la Figura 1. </li><li> Densificar el electrodo de CNT sobre la superficie mediante la aplicación de metoxi-nonafluorobutano (C 4 F 9 OCH 3) (HFE) y recubriendo la CNT con una pequeña amount del líquido y luego dejar que se seque. </li><li> Limpie el polímero y CNT en la parte superior de la ITO y vidrio que tendrá el electrodo de puerta como se muestra en el tercer panel de la Figura 1. Retire todo el polímero desde el cristal para evitar fugas de puerta con una hoja de afeitar. </li><li> Lamine el electrodo de puerta de la CNT en el área limpiada de los sustratos PTB7 y P3HT recubiertos. Lamine el MWCNT tirando del borde del bosque MWCNT con una hoja de afeitar y dejar que la hoja de pie libremente entre unos tubos capilares. Pase el dispositivo a través de la hoja independiente para laminar la CNT en el dispositivo. El electrodo de puerta debe tener 2-3 veces el número de capas tal como se establece en el electrodo común. </li><li> Densificar el electrodo de puerta con HFE. </li></ol></li><li> Colocar una pequeña gota (≈10 l) de líquido iónico, N, N -dietil- N-metil-N - (2-metoxietil) tetrafluoroborato de amonio, DEME-BF 4, en la parte superior de ambos electrodos de CNT unode los sustratos. </li><li> Colocar con cuidado el sustrato sin líquido iónico en la parte superior del sustrato con líquido iónico con los electrodos comunes de puerta y en la parte superior de cada-otro. Esto se muestra en el último panel de la Figura 1. </li><li> Coloque una fotomáscara con un tamaño de abertura más pequeño que el tamaño del electrodo sobre el área activa. Use pequeños clips para mantener la fotomáscara en su lugar, así como para mantener el dispositivo juntos durante la prueba. </li></ol> 4. Medir el dispositivo <ol><li> Transferir el dispositivo en la guantera de medición. </li><li> Realice las conexiones eléctricas. <ol><li> Conecte la fuente de suministro de puerta entre el electrodo común y el electrodo de puerta con el común como suelo. </li><li> Conectar los dos ánodos de ITO a los cables que están conectados a un conmutador que permite la selección de cualquiera de ánodo o ánodos ambos. </li><li> Conecte la salida del interruptor a la entrada de la unidad de medida de fuente. </li><li> Conecte el suelo de las meas de origenunidad ure al electrodo común. </li></ol></li><li> Mida las características IV del dispositivo mediante la repetición de los siguientes pasos para ascender V Puerta. <ol><li> Set V Puerta al siguiente valor, a partir de V = 0 V Puerta a Puerta V = 2 V en incrementos de 0,25 V. </li><li> Espere 5 minutos o hasta que se estabiliza la corriente de puerta. Lo ideal sería que la corriente de puerta debería estabilizarse en torno a 10s de nanoamperios. </li><li> Ajuste el conmutador en ambas sub-células. </li><li> Abra el obturador de la lámpara. </li><li> Ejecutar un barrido de tensión en la unidad de medida de voltios fuente de -1 a +1 voltios en incrementos de alrededor de 100 o más. </li><li> Ejecutar un barrido de tensión de 1 volt a -1 voltio. </li><li> Cierre el obturador de la lámpara. </li><li> Ejecute los barridos de tensión de nuevo. </li><li> Ajuste el conmutador en la sub-celular frente. </li><li> Repita los pasos 4.3.4 al 4.3.8. </li><li> Ajuste el conmutador en la sub-celular de vuelta. </li><li> Repita los pasos 4.3.4 al 4.3.8. </li></ol></li><li> Calcular los parámetros del dispositivo. &lt;ol&gt; <li> Encuentra la corriente de cortocircuito (J SC) de cada sub-celular en cada puerta de V mediante la búsqueda de la corriente producida por el dispositivo cuando el voltaje a través de la sub-celular es 0 V. </li><li> Encuentra la tensión de circuito abierto (V OC) de cada sub-celular en cada puerta de V mediante la búsqueda de la tensión producida por el dispositivo cuando la corriente a través de la sub-celular es 0 A. </li><li> Encuentra la salida de potencia máxima de la célula solar multiplicando cada valor de la tensión con cada valor actual y seleccionando el valor máximo (más negativo). Esto supone que se mide la corriente actual como negativa la foto-generado. </li><li> Encuentra la eficiencia de conversión de potencia (η) dividiendo la potencia máxima por la potencia de la luz de entrada. </li><li> Calcula el factor de llenado (FF) dividiendo la potencia máxima por el producto de J SC y V OC. </li></ol></li></ol>

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The authors have nothing to disclose.

Los resultados ponen de manifiesto algunas consideraciones en el diseño de células solares en tándem paralelo. Cabe destacar que, si uno de los sub-células está realizando mal, el rendimiento en tándem afectada negativamente. Los resultados muestran que hay dos efectos principales. Si está en corto un sub-celular, por ejemplo, muestra un comportamiento óhmico, el FF T no será mayor que el FF de la mala sub-celular. J T SC y V T OC se verán afectad...

Semiconductores de polímero son los fotovoltaicos orgánica (OPV) materiales principales debido a la alta capacidad de absorción, buenas propiedades de transporte, la flexibilidad, y la compatibilidad con sustratos sensibles a la temperatura. Dispositivos OPV eficiencia de conversión de energía, η, se han subido significativamente en los últimos años, con eficiencias de células individuales de hasta 9.1% 1, por lo que una tecnología de energía cada vez más viable. A pesar de las mejoras en η, los espesores de las capas delgadas activos óptimos de los dispositivos limitan la absorción de luz y dificultan la fabricación confiable. Además, la anchura espectral de absorción de la luz de cada polímero está limitada en comparación con materiales inorgánicos. Polímeros de emparejamiento de diferente sensibilidad espectral no pasa por estas dificultades, por lo que las arquitecturas tándem 2 una innovación necesaria. Dispositivos en tándem de la serie son la arquitectura tándem más común. En este diseño, un materi de transporte de electronesal, una capa de recombinación metálica opcional, y una capa de transporte de huecos se conectan dos capas fotoactivas independientes llamados sub-células. La vinculación de sub-células en una configuración en serie aumenta la tensión de circuito abierto del dispositivo de combinación. Algunos grupos han tenido éxito con capas de transporte dopadas degeneradamente de 3 - 5, pero más grupos han utilizado partículas de oro o plata para ayudar a la recombinación de huecos y electrones en la capa intermedia 6,7. En contraste, los tándems paralelas requieren un electrodo de alta conductividad, ya sea ánodo o cátodo, que une las dos capas activas. La capa intermedia debe ser altamente transparente, lo que limita la serie en tándem capas intermedias que contienen partículas metálicas, y más aún para las capas intermedias en tándem paralelas, compuestas de electrodos de metal delgada y continua. Los nanotubos de carbono (CNT) hojas muestran mayor transparencia de capas de metal. Así que el Instituto NanoTech, en colaboración con la Universidad de Shimane, tiene introducido el concepto de usar como el electrodo en capa intermedia, dispositivos en tándem paralelas monolíticos 8. Los esfuerzos previos del momento, OPV, dispositivos tándem paralelas monolíticas con hojas de la CNT que funcionan como ánodos de capa intermedia 8,9. Estos métodos requieren un cuidado especial para evitar el cortocircuito de una o dos células o capas precedentes perjudiciales al depositar capas posteriores. El nuevo método descrito en este documento facilita la fabricación colocando el electrodo de CNT en la parte superior de las capas activas poliméricos de dos células individuales, a continuación, laminación de los dos dispositivos separados entre sí como se muestra en la Figura 1. Este método es notable como el dispositivo, incluyendo un aire -stable cátodo CNT, puede ser fabricado en su totalidad en las condiciones ambientales que emplea sólo el procesamiento seco y la solución. Hojas de CNT no son intrínsecamente buenas cátodos, ya que requieren el dopaje de tipo n para disminuir la función de trabajo a fin de recoger los electrones de la región fotoactivade una célula solar 10. Eléctrico de doble capa de carga en un electrolito, tal como un líquido iónico, se puede utilizar para cambiar la función de trabajo de CNT electrodos 11-14. Como se describe en un documento anterior y 15 representado en la Figura 2, cuando el voltaje de puerta (V GATE) está aumenta, la función de trabajo del electrodo común CNT se disminuye, creando asimetría del electrodo. Esto evita que la colección agujero de donante de la vacuna antipoliomielítica oral en favor de la recogida de electrones del aceptador de la OPV, y los dispositivos de encender, cambiar de fotoresistor ineficiente en fotodiodo 15 comportamiento. También debe tenerse en cuenta que la energía utilizada para cargar el dispositivo y la potencia perdida debido a las corrientes de fuga puerta es trivial en comparación con la energía generada por la célula solar 15. Gating iónica de electrodos CNT tiene un gran efecto sobre la función de trabajo debido a la baja densidad de estados y el altorelación de superficie a volumen en los electrodos de la CNT. Métodos similares se han utilizado para mejorar una barrera Schottky en la interfase de CNT con n-Si 16.

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			<td height="25" style="height:25px;">phenyl-C61 -butyric&#160; acid methyl&#160; ester</td>
			<td style="width:191px;">1- Material</td>
			<td style="width:119px;">PC61BM</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b&#8242;]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl})&#160;</td>
			<td style="width:191px;">1- Material</td>
			<td style="width:119px;">PTB7</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">phenyl-C61 -butyric acid methyl&#160; ester</td>
			<td style="width:191px;">Solenne</td>
			<td style="width:119px;">PC71BM</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1,8-Diiodooctane</td>
			<td style="width:191px;">Sigma Aldrich</td>
			<td align="right" style="width:119px;">250295</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Chlorobenzene</td>
			<td style="width:191px;">Sigma Aldrich</td>
			<td align="right" style="width:119px;">284513</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Indium Tin Oxide Coated Glass 15 Ohm/SQ</td>
			<td style="width:191px;">Lumtec</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">S1813</td>
			<td style="width:191px;">UTD Cleanroom</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">MF311</td>
			<td style="width:191px;">UTD Cleanroom</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HCl</td>
			<td style="width:191px;">UTD Cleanroom</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Acetone</td>
			<td style="width:191px;">Fisher Scientific</td>
			<td style="width:119px;">A18-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Toluene</td>
			<td style="width:191px;">Fisher Scientific</td>
			<td style="width:119px;">T323-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Methanol</td>
			<td style="width:191px;">BDH</td>
			<td style="width:119px;">BDH1135-19L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Isopropanol</td>
			<td style="width:191px;">Fisher Scientific</td>
			<td style="width:119px;">A416-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">CEE Spincoater</td>
			<td style="width:191px;">Brewer Scientific</td>
			<td style="width:119px;"></td>
			<td>http://www.utdallas.edu/research/cleanroom/tools/CEESpinCoater.htm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Contact Printer</td>
			<td style="width:191px;">Quintel</td>
			<td style="width:119px;">Q4000-6</td>
			<td>http://www.utdallas.edu/research/cleanroom/QuintelPrinter.htm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">CPK Spin Processor</td>
			<td style="width:191px;"></td>
			<td style="width:119px;"></td>
			<td>http://www.utdallas.edu/research/cleanroom/tools/CPKsolvent.htm</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:312px;">Spin Coater</td>
			<td style="width:191px;">Laurell</td>
			<td style="width:119px;">WS-400-6NPP/LITE</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Glove Box</td>
			<td style="width:191px;">M-Braun</td>
			<td style="width:119px;">Lab Master 130</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Solar Simulator</td>
			<td style="width:191px;">Thermo Oriel/Newport</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Keithley 2400 SMU</td>
			<td style="width:191px;">Keithley/Techtronix</td>
			<td align="right" style="width:119px;">2400</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Keithley 7002 Multiplexer</td>
			<td style="width:191px;">Keithley/Techtronix</td>
			<td align="right" style="width:119px;">7002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Ultrasonic Cleaner</td>
			<td style="width:191px;">Kendal</td>
			<td style="width:119px;">HB-S-49HDT</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:312px;">Micropipette</td>
			<td style="width:191px;">Eppendorf</td>
			<td style="width:119px;">200uL</td>
			<td></td>
		</tr>
	</tbody>
</table>

ambient method for the production of an ionically gated carbon nanotube common cathode in tandem organic solar cells

A method of fabricating organic photovoltaic (OPV) tandems that requires no vacuum processing is presented. These devices are comprised of two solution-processed polymeric cells connected in parallel by a transparent carbon nanotubes (CNT) interlayer. This structure includes improvements in fabrication techniques for tandem OPV devices. First the need for ambient-processed cathodes is considered. The CNT anode in the tandem device is tuned via ionic gating to become a common cathode. Ionic gating employs electric double layer charging to lower the work function of the CNT electrode. Secondly, the difficulty of sequentially stacking tandem layers by solution-processing is addressed. The devices are fabricated via solution and dry-lamination in ambient conditions with parallel processing steps. The method of fabricating the individual polymeric cells, the steps needed to laminate them together with a common CNT cathode, and then provide some representative results are described. These results demonstrate ionic gating of the CNT electrode to create a common cathode and addition of current and efficiency as a result of the lamination procedure.

Un dispositivo tándem formado a partir de diferentes polímeros, particularmente polímeros de diferentes significativamente las brechas de la banda, es de interés práctico, ya que estos dispositivos pueden absorber el rango espectral de la luz más grande. En esta estructura del dispositivo, el sub-celular PTB7 es la célula hacia atrás y P3HT es la sub-celular frente. Con ello se pretende absorber la mayor cantidad de luz que la sub-celular P3HT es en gran medida transparente a la luz de longitud de onda más larg...

Watch this Scientific Journal Video about Ambient Method for the Production of an Ionically Gated Carbon Nanotube Common Cathode in Tandem Organic Solar Cells at JoVE.com

Ambient Method for the Production of an Ionically Gated Carbon Nanotube Common Cathode in Tandem Organic Solar Cells

A method of fabricating, in ambient conditions, organic photovoltaic tandem devices in a parallel configuration is presented. These devices feature an air-processed, semi-transparent, carbon nanotube common cathode.

Método ambiente para la producción de un cátodo común iónicamente cerrada nanotubos de carbono en las células solares en tándem Orgánica

A method of fabricating organic photovoltaic (OPV) tandems that requires no vacuum processing is presented. These devices are comprised of two ...

ambient-method-for-production-an-ionically-gated-carbon-nanotube

Research

JoVE Journal

Engineering

9.3K vistas.  The University of Texas at Dallas. A method of fabricating, in ambient conditions, organic photovoltaic tandem devices in a parallel configuration is presented. These devices feature an air-processed, semi-transparent, carbon nanotube common cathode.

Video: Ambient Method for the Production of an Ionically Gated Carbon Nanotube Common Cathode in Tandem Organic Solar Cells

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult1. At the same time, the ability to do so is highly important in view of a number of applications in functional soft matter including electronics, biomedical engineering, and sensors. In the past, successful strategies to control the size and shape of supramolecular polymers typically focused on the use of templates2,3, end cappers4 or selective solvent techniques5. 
Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing electrostatic repulsive interactions on the hydrophilic rim and attractive non-covalent forces within the hydrophobic core of the polymerizing building block, we manage to create small and discrete spherical objects6,7. Increasing the salt concentration to screen the charges induces a sphere-to-rod transition. Intriguingly, this transition is expressed in an increase of cooperativity in the temperature-dependent self-assembly mechanism, and more stable aggregates are obtained. 
For our study we select a benzene-1,3,5-tricarboxamide (BTA) core connected to a hydrophilic metal chelate via a hydrophobic, fluorinated L-phenylalanine based spacer (Scheme 1). The metal chelate selected is a Gd(III)-DTPA complex that contains two overall remaining charges per complex and necessarily two counter ions. The one-dimensional growth of the aggregate is directed by &pi;-&pi; stacking and intermolecular hydrogen bonding. However, the electrostatic, repulsive forces that arise from the charges on the Gd(III)-DTPA complex start limiting the one-dimensional growth of the BTA-based discotic once a certain size is reached. At millimolar concentrations the formed aggregate has a spherical shape and a diameter of around 5 nm as inferred from 1H-NMR spectroscopy, small angle X-ray scattering, and cryogenic transmission electron microscopy (cryo-TEM). The strength of the electrostatic repulsive interactions between molecules can be reduced by increasing the salt concentration of the buffered solutions. This screening of the charges induces a transition from spherical aggregates into elongated rods with a length &gt; 25 nm. Cryo-TEM allows to visualise the changes in shape and size. In addition, CD spectroscopy permits to derive the mechanistic details of the self-assembly processes before and after the addition of salt. Importantly, the cooperativity -a key feature that dictates the physical properties of the produced supramolecular polymers- increases dramatically upon screening the electrostatic interactions. This increase in cooperativity results in a significant increase in the molecular weight of the formed supramolecular polymers in water.

The goal of this experiment is to determine and control the size, shape and stability of self-assembled discotic amphiphiles in water. For aqueous based supramolecular polymers such level of control is very difficult. We apply a strategy using both repulsive and attractive interactions. The experimental techniques applied to characterize this system are broadly applicable.

Controlar el tamaño, forma y estabilidad de los polímeros supramoleculares en el agua

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult1. At the same time, the ability to do ...

Investigación

Ingeniería

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. 
Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3.

We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.

Fabricación, densificación, y la réplica de Moldeo por inyección de microestructuras 3D nanotubos de carbono

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip ...

Dry Oxidation and Vacuum Annealing Treatments for Tuning the Wetting Properties of Carbon Nanotube Arrays

In this article, we describe a simple method to reversibly tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays. Here, CNT arrays are defined as densely packed multi-walled carbon nanotubes oriented perpendicular to the growth substrate as a result of a growth process by the standard thermal chemical vapor deposition (CVD) technique.1,2 These CNT arrays are then exposed to vacuum annealing treatment to make them more hydrophobic or to dry oxidation treatment to render them more hydrophilic. The hydrophobic CNT arrays can be turned hydrophilic by exposing them to dry oxidation treatment, while the hydrophilic CNT arrays can be turned hydrophobic by exposing them to vacuum annealing treatment. Using a combination of both treatments, CNT arrays can be repeatedly switched between hydrophilic and hydrophobic.2 Therefore, such combination show a very high potential in many industrial and consumer applications, including drug delivery system and high power density supercapacitors.3-5
The key to vary the wettability of CNT arrays is to control the surface concentration of oxygen adsorbates. Basically oxygen adsorbates can be introduced by exposing the CNT arrays to any oxidation treatment. Here we use dry oxidation treatments, such as oxygen plasma and UV/ozone, to functionalize the surface of CNT with oxygenated functional groups. These oxygenated functional groups allow hydrogen bond between the surface of CNT and water molecules to form, rendering the CNT hydrophilic. To turn them hydrophobic, adsorbed oxygen must be removed from the surface of CNT. Here we employ vacuum annealing treatment to induce oxygen desorption process. CNT arrays with extremely low surface concentration of oxygen adsorbates exhibit a superhydrophobic behavior.

This article describes a simple method to fabricate vertically aligned carbon nanotube arrays by CVD and to subsequently tune their wetting properties by exposing them to vacuum annealing or dry oxidation treatment.

La oxidación en seco y vacío Recocido Tratamientos para Ajuste las propiedades humectantes de conjuntos de nanotubos de carbono

In this article, we describe a simple method to reversibly  tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays.  Here, CNT ...

Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers

Nitrogen-doped carbon nanotubes consist of many cup-shaped graphitic compartments termed as nitrogen-doped carbon nanotube cups (NCNCs). These as-synthesized graphitic nanocups from chemical vapor deposition (CVD) method were stacked in a head-to-tail fashion held only through noncovalent interactions. Individual NCNCs can be isolated out of their stacking structure through a series of chemical and physical separation processes. First, as-synthesized NCNCs were oxidized in a mixture of strong acids to introduce oxygen-containing defects on the graphitic walls. The oxidized NCNCs were then processed using high-intensity probe-tip sonication which effectively separated the stacked NCNCs into individual graphitic nanocups. Owing to their abundant oxygen and nitrogen surface functionalities, the resulted individual NCNCs are highly hydrophilic and can be effectively functionalized with gold nanoparticles (GNPs), which preferentially fit in the opening of the cups as cork stoppers. These graphitic nanocups corked with GNPs may find promising applications as nanoscale containers and drug carriers.

We discussed the synthesis of individual graphitic nanocups using a series of techniques including chemical vapor deposition, acid oxidation and probe-tip sonication. By citrate reduction of HAuCl4, the graphitic nanocups were effectively corked with gold nanoparticles due to the chemically reactive edges of the cups.

Síntesis y funcionalización de nitrógeno dopados Copas de nanotubos de carbono con nanopartículas de oro como tapones de corcho

Nitrogen-doped carbon  nanotubes consist of many cup-shaped graphitic compartments termed as  nitrogen-doped carbon nanotube cups (NCNCs).  These ...

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.

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.

Uso de neutron spin echo resuelto grazing incidencia dispersión para investigar materiales orgánicos de células solares

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

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

Fabricación de Baja Temperatura de nanotubos de carbono Interconexiones verticales Compatible con la tecnología de semiconductores

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

La cuantificación de las concentraciones de hidrógeno en superficies e interfaces de capas y materiales a granel a través de perfiles de profundidad con el análisis de Reacción nuclear

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 &#181;m thick layer. The resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The binder-free formulation resulted in a reduced processing temperature of 250 &#176;C, compatible with flexible polyamide substrates which are stable up to temperatures of 350 &#730;C. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye sensitized solar cells.

This paper investigates the suitability of inkjet printing for the manufacturing of dye-sensitized solar cells. A binder-free TiO2 nanoparticle ink was formulated and printed onto a FTO glass substrate. The printed layer was fabricated into a cell with an active area of 0.25 cm2 and an efficiency of 3.5%.

Impresión digital de dióxido de titanio para células solares sensibilizadas Tinte

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less ...

Morphology Control for Fully Printable Organic&#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting material. However, fullerene derivatives are air-sensitive; therefore, air-stable material is needed as an alternative. In the present study, we propose and describe the properties of Ti-alkoxide as an alternative electron-accepting material to fullerene derivatives to create highly air-stable BHJ solar cells. It is well-known that controlling the morphology in the photoactive layer, which is constructed with fullerene derivatives as the electron acceptor, is important for obtaining a high overall efficiency through the solvent method. The conventional solvent method is useful for high-solubility materials, such as fullerene derivatives. However, for Ti-alkoxides, the conventional solvent method is insufficient, because they only dissolve in specific solvents. Here, we demonstrate a new approach to morphology control that uses the molecular bulkiness of Ti-alkoxides without the conventional solvent method. That is, this method is one approach to obtain highly efficient, air-stable, organic-inorganic bulk-heterojunction solar cells.

Morphology Control for Fully Printable Organic&amp;#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

A method for fully printable, fullerene-free, highly air-stable, bulk-heterojunction solar cells based on Ti alkoxides as the electron acceptor and the electron-donating polymer fabrication is described here. Moreover, a method for controlling the morphology of the photoactive layer through the molecular bulkiness of the Ti-alkoxide units is reported.

Control de la morfología de las células solares a granel-heterounión orgánica-inorgánica completamente para imprimir Sobre la base de un Ti-alcóxido y semiconductores de polímero

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting ...

Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning electron microscope (ESEM) operating with a low pressure water vapor ambient. In this technique, a portion of the electron beam interacts with the water vapor in the vicinity of the CNT sample, dissociating the water molecules into hydroxyl radicals and other species by radiolysis. The remainder of the electron beam interacts with the CNT forest sample, making it susceptible to oxidation from the chemical products of radiolysis. This technique may be used to trim a selected region of an individual CNT, or it may be used to remove hundreds of cubic microns of material by adjusting ESEM parameters. The machining resolution is similar to the imaging resolution of the ESEM itself. The technique produces only small quantities of carbon residue along the boundaries of the cutting zone, with minimal effect on the native structural morphology of the CNT forest.

Low pressure scanning electron microscopy in a water vapor ambient is used to machine nanoscale to microscale features in carbon nanotube forests.

Fresado de precisión de nanotubos de carbono de los bosques El uso de baja presión de barrido Microscopía Electrónica

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning ...