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Formación de centros de color de larga duración para la emisión de luz visible de banda ancha en perovskitas

Edward P Booker¹, Tudor H Thomas¹, Claudio Quarti²

¹Cavendish Laboratory, University of Cambridge , CB3 0HE Cambridge, United Kingdom.

Journal of the American Chemical Society

|November 21, 2017

Resumen

Descubrimos que la emisión visible de banda ancha en las perovskitas híbridas se origina en defectos de yoduro, no sólo en orientaciones específicas de los cristales. El control de estos defectos es clave para diseñar emisores de luz blanca.

Área de la Ciencia:

Ciencias de los materiales
Física de la materia condensada
Química del estado sólido

Sus antecedentes:

Las perovskitas híbridas de plomo en capas exhiben propiedades fotofísicas únicas.
La emisión visible de banda ancha se observa en algunos sistemas de perovskita, pero su origen no se comprende completamente.
Comprender los mecanismos de emisión es crucial para el desarrollo de nuevos dispositivos optoelectrónicos.

Objetivo del estudio:

Investigar el origen de la emisión visible de banda ancha en las perovskitas de plomo yodado de hexilamonio (HA) y dodecilamonio (DA) orientadas 001.
Correlación de las propiedades de emisión con las características estructurales y fotofísicas.
Determinar el papel de los defectos en la emisión de baja energía.

Principales métodos:

Simulaciones de la teoría funcional de la densidad (DFT) de los primeros principios.
Espectroscopia de fotoluminiscencia con resolución de tiempo y estado estacionario.
Espectroscopia de absorción transitoria ultrarrápida.
Mediciones de difracción de rayos X (XRD) desde 300 K hasta 4 K.

Principales resultados:

Se observó una banda de emisión de banda ancha desplazada hacia el rojo (FWHM ~ 0.4 eV) por debajo de 200 K tanto en HA2PbI4 como en DA2PbI4.
El tiempo de vida de esta emisión de sub-banda-brecha es órdenes de magnitud más largo que la transición excitónica.
El XRD reveló cambios dependientes de la temperatura en la inclinación octaédrica y el espaciamiento de la celosía, incluida una transición de fase en DA2PbI4 alrededor de 200 K.
Las simulaciones DFT identificaron los defectos intersticiales de yoduro y Frenkel como la fuente de emisión de baja energía en HA2PbI4.

Conclusiones:

La emisión de luz blanca de banda ancha es una propiedad general de las perovskitas híbridas 2D, no limitada a orientaciones o composiciones específicas.
La emisión de baja energía se atribuye a defectos, particularmente defectos intersticiales de yoduro y de Frenkel.
El control de defectos es esencial para adaptar las propiedades de emisión de luz blanca en los materiales de perovskita.

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