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Separación de carga en dos pasos que pasa a través del estado de transferencia de carga parcial en una diada
Taeyeon Kim1, Woojae Kim1, Olena Vakuliuk2
1Department of Chemistry and Spectroscopy Laboratory for Functional π-Electronic Systems , Yonsei University , Seoul 03722 , Korea.
Journal of the American Chemical Society
|December 24, 2019
Resumen
Descubrimos un proceso de separación de cargas en dos pasos en una nueva díada de ditopirrolopirrol-pirrolopirrol. Este mecanismo, que implica un estado de transferencia de carga parcial, es crucial para la separación eficiente de cargas en la electrónica orgánica.
Área de la Ciencia:
- Fotofísica molecular y dinámica de transferencia de carga.
Sus antecedentes:
- La separación de cargas (CS) se observa típicamente en sistemas de donante-aceptante de acoplamiento débil.
- Comprender los estados intermedios en CS es vital para optimizar los dispositivos moleculares.
Objetivo del estudio:
- Investigar un nuevo proceso de separación de cargas en dos pasos en una díada de dicetopirrolopirrol-pirrolopirrol (DPP-PP) sintetizada.
- Aclarar el papel de los estados de transferencia parcial de carga (CT) en la separación eficiente de la carga.
Principales métodos:
- Se utilizó la absorción transitoria, la conversión ascendente de fluorescencia y la espectroscopia Raman estimulada por impulso transitoria.
- Se analizaron los espectros de absorción en estado excitado y el apagado por fluorescencia.
- Cambios de frecuencia vibratoria investigados para cuantificar el carácter de la TC.
Principales resultados:
- Se observó un proceso de CS de dos pasos iniciado por fotoexcitación, que pasa por un estado parcial de CT antes de alcanzar el estado final de CS.
- Tiempos de relajación determinados hasta el estado parcial CT influenciados por las fluctuaciones del disolvente y de la estructura (1-20 ps en el tolueno, 700 fs en el THF).
- Características de la TC cuantificadas de los estados luminosos y parciales de la TC (0,1 e y 0,5 e, respectivamente) mediante análisis de la frecuencia vibratoria.
Conclusiones:
- La díada DPP-PP exhibe una separación de carga eficiente a través de un estado de CT parcial distinto, facilitado por una fuerte comunicación electrónica dentro del núcleo de pirrolo [3,2-b] pirrol.
- Este mecanismo ofrece aplicaciones potenciales en la energía fotovoltaica orgánica y los diodos emisores de luz.
- El estudio proporciona información cuantitativa sobre la dinámica de la TC y la influencia de la estructura molecular en la eficiencia de la separación de cargas.
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