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Una imagen completa de la dinámica catiónica en materiales híbridos de perovskita a partir de la espectroscopia de

Aditya Mishra¹, Michael A Hope¹, Michael Grätzel¹

¹Institut des Sciences et Ingéniere Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015Lausanne, Switzerland.

Journal of the American Chemical Society

|December 29, 2022

Resumen

Los cationes orgánicos en las células solares de perovskita giran rápidamente, lo que influye en el rendimiento. Este estudio cuantifica la dinámica catiónica utilizando RMN, revelando tiempos de rotación de picosegundos y conocimientos para el diseño de células solares de perovskita eficientes.

Área de la Ciencia:

Ciencias de los materiales
Química del estado sólido
Optoelectrónica y sus derivados

Sus antecedentes:

Las perovskitas híbridas orgánicas e inorgánicas son cruciales para las células solares debido a sus propiedades optoelectrónicas.
La dinámica de los cationes orgánicos dentro de la red inorgánica tiene un impacto significativo en el rendimiento del dispositivo.
Comprender estas dinámicas es clave para optimizar la eficiencia de las células solares de perovskita.

Objetivo del estudio:

Proporcionar un análisis cuantitativo de la dinámica de los cationes orgánicos en las perovskitas a base de formamidinio y de cationes mixtos.
Para determinar la energía de activación y los tiempos de correlación para la rotación del catión.
Para correlacionar la dinámica catiónica con la composición y estructura de perovskita para mejorar el diseño de células solares.

Principales métodos:

Se utilizó la relajometría NMR cuadrupolar de estado sólido de 2H y 14N.
Empleó el giro de ángulo mágico para analizar la rotación del catión.
Se han investigado los cationes de metilamonio (MA+), formamidinio (FA+) y guanidinio (GUA+).

Principales resultados:

Todos los cationes investigados (MA +, FA +, GUA +) muestran una rotación en la escala de picosegundos a temperatura ambiente.
MA + y GUA + muestran componentes de rotación adicionales más rápidos y más lentos, respectivamente.
La dinámica catiónica está influenciada por la simetría de la red inorgánica, pero no por los niveles de sustitución catiónica; La rotación FA + es invariante por encima de la transición de fase.

Conclusiones:

La caracterización precisa de la dinámica catiónica proporciona una comprensión más profunda de su papel en las propiedades optoelectrónicas de la perovskita.
Las ideas obtenidas guiarán el diseño de células solares de perovskita más eficientes.
Se identificó un mecanismo de relajación inusual para MA+ en composiciones específicas de perovskita debido a la difusión a defectos paramagnéticos.

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