Optical studies of trapped carrier dynamics in water oxidation photoanodes
File(s)
Author(s)
Meng, Zhu
Type
Thesis
Abstract
The widespread occurrence and diversity of defects in photoelectrochemical photoelectrodes makes it imperative to fully grasp and anticipate the correlation between defects and photocatalytic performance. Defects within photoelectrodes influencing processes ranging from light absorption to carrier transport and reaction kinetics. In this thesis, we examine metal oxides as well as organic polymers as representative photoelectrodes. We employ advanced absorption and photocurrent spectroscopy to unveil the intricated impact of defects on carrier transport. Furthermore, we explore the potential for enhancing photoconversion performance through infrared optical control.
The majority of the research in this thesis was dedicated to observing the dynamics of trapped carriers in metal oxides during operando water oxidation. The results reveal that ultrafast polaron formation and intrinsic defect-induced trapping impose limitations on the effective separation and extraction of carriers. This constraint is observable not only within the bulk of the material but also at the interface of the bismuth vanadate photoanode after transport-assisted trapping. The application of an external bias enhances carrier hopping but does not alleviate interface trapping until a sufficient degree of band bending is reached. The existence of trapped carriers constitutes one of the fundamental origins of the overpotential requirement.
The remainder of the thesis further explored the infrared induced carrier transport and device performance change. The near-infrared region is not exploited enough on optical control of semiconductor materials. We successfully observed infrared de-trapping processes in transient absorption and photocurrent measurements...
The majority of the research in this thesis was dedicated to observing the dynamics of trapped carriers in metal oxides during operando water oxidation. The results reveal that ultrafast polaron formation and intrinsic defect-induced trapping impose limitations on the effective separation and extraction of carriers. This constraint is observable not only within the bulk of the material but also at the interface of the bismuth vanadate photoanode after transport-assisted trapping. The application of an external bias enhances carrier hopping but does not alleviate interface trapping until a sufficient degree of band bending is reached. The existence of trapped carriers constitutes one of the fundamental origins of the overpotential requirement.
The remainder of the thesis further explored the infrared induced carrier transport and device performance change. The near-infrared region is not exploited enough on optical control of semiconductor materials. We successfully observed infrared de-trapping processes in transient absorption and photocurrent measurements...
Version
Open Access
Date Issued
2023-08-31
Date Awarded
01/12/2023
License URL
Advisor
Artem, Bakulin
Durrant, James
Kafizas, Andreas
Sponsor
China Scholarship Council
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)