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Control de los portadores de carga atrapamiento y relajación en hematita por carga vacante de oxígeno: Ab Initio
Zhaohui Zhou1,2, Jin Liu2, Run Long3
1International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University , Xi'an 710049, China.
Journal of the American Chemical Society
|April 27, 2017
Resumen
La recombinación de carga ultrarrápida en hematita (α-Fe2O3) dificulta las aplicaciones de energía solar. Las vacantes de oxígeno (Ov) impactan en la dinámica de recombinación, con defectos de Ov ionizados que mejoran la vida útil del portador de carga para mejorar el rendimiento del fotoánodo.
Área de la Ciencia:
- Ciencias de los materiales
- Química computacional
- Energía renovable
Sus antecedentes:
- La recombinación de carga ultrarrápida en hematita (α-Fe2O3) limita su eficiencia en tecnologías de conversión de energía solar como la división fotoelectroquímica del agua.
- La comprensión de la dinámica del portador de carga, en particular la recombinación de agujeros de electrones, es crucial para optimizar los fotoánodos basados en hematita.
Objetivo del estudio:
- Investigar la dinámica de relajación de la carga en el dominio temporal en hematita (α-Fe2O3) con y sin defectos de vacío de oxígeno (Ov).
- Para aclarar los mecanismos de recombinación de electrones-agujero y el papel de los defectos Ov en la influencia de estos procesos.
Principales métodos:
- Empleó simulaciones ab initio de dominio temporal utilizando dinámicas moleculares no adiabáticas dentro de la teoría funcional de densidad dependiente del tiempo.
- Estudió la dinámica de relajación de la carga tanto en celosías de hematita prístinas como en las que contenía Ov.
Principales resultados:
- El atrapamiento de agujeros se identifica como el paso que limita la velocidad en la recombinación de electrones con agujeros tanto para los sistemas Ov neutros como para los ionizados.
- Los defectos neutros de Ov aceleran significativamente la recombinación (aprox. 30x), mientras que los defectos de Ov ionizados lo disminuyen (aprox. 10x) en comparación con Ov neutro, mejorando la conductividad y la vida útil del portador.
- Las simulaciones reproducen con precisión las escalas de tiempo experimentales para el enfriamiento, el atrapamiento y la recombinación del portador caliente.
Conclusiones:
- La ionización del vacío de oxígeno en la hematita es vital para mejorar la conductividad eléctrica y la vida útil del portador de carga en los fotoánodos.
- El estudio proporciona información atómica sobre la dinámica del portador en hematita, explicando la mejora del rendimiento de los fotoánodos modificados por Ov.
- Identificaron dos mecanismos potenciales para la recombinación de electrones con agujero asistido por Ov.
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