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Reacciones de recombinación de carga y aniquilación de excitones en mezclas de polímeros conjugados

Ian A Howard¹, Justin M Hodgkiss, Xinping Zhang

¹Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.

Journal of the American Chemical Society

|December 8, 2009

Resumen

Las interacciones bimoleculares en las películas de polímeros son clave para la optoelectrónica. Las interacciones de excitación-carga son eficientes, mientras que la recombinación de carga y la aniquilación tripleta-tripleta son mínimas debido a la movilidad y difusión restringidas.

Área de la Ciencia:

La optoelectrónica es la óptica electrónica.
Ciencia de los materiales Ciencia de los materiales.
La fotofísica es la fotofísica.

Sus antecedentes:

Las interacciones bimoleculares en las películas de polímeros conjugados tienen un impacto significativo en la eficiencia de los dispositivos optoelectrónicos a altas densidades de excitación.
Comprender estas interacciones es crucial para diseñar materiales avanzados para aplicaciones como diodos orgánicos emisores de luz y células solares.

Objetivo del estudio:

Para investigar las interacciones bimoleculares de cargas, excitones singlet y excitones triplet en mezclas de polifluoreno.
Para dilucidar los mecanismos que rigen los procesos de recombinación y aniquilación en materiales poliméricos nanoestructurados.

Principales métodos:

Utilizó espectroscopia óptica de resolución temporal para medir las interacciones bimoleculares.
Se estudiaron mezclas de polifluoreno íntimamente mezcladas con compensaciones de borde de banda optimizadas para la transferencia de electrones fotoinducida.

Principales resultados:

Se descubrió que las interacciones excitón-carga son altamente eficientes, con la aniquilación de excitones individuales por cargas que ocurren en escalas de tiempo de picosegundos.
La recombinación de carga bimolecular y la aniquilación triple-triple fueron insignificantes, atribuidas a la limitada movilidad del portador de carga y a la difusión restringida de los tripletes.
Se pueden mantener densidades extremadamente altas de pares de cargas en la mezcla.

Conclusiones:

La velocidad y la naturaleza de las interacciones bimoleculares se rigen por la distribución estocástica de excitación y la conectividad limitada entre dominios.
Un modelo cuantitativo basado en estos factores explica los fenómenos observados.
Los hallazgos ofrecen un marco integral para comprender la recombinación y la aniquilación en materiales nanoestructurados.

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