Master of Science, Institut National Polytechnique (2012)
Doctor of Philosophy, Universitat Jaume (2016)
Alberto Salleo, Postdoctoral Faculty Sponsor
Investigating the Consistency of Models for Water Splitting Systems by Light and Voltage Modulated Techniques
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2017; 8 (1): 172-180
The optimization of solar energy conversion devices relies on their accurate and nondestructive characterization. The small voltage perturbation techniques of impedance spectroscopy (IS) have proven to be very powerful to identify the main charge storage modes and charge transfer processes that control device operation. Here we establish the general connection between IS and light modulated techniques such as intensity modulated photocurrent (IMPS) and photovoltage spectroscopies (IMVS) for a general system that converts light to energy. We subsequently show how these techniques are related to the steady-state photocurrent and photovoltage and the external quantum efficiency. Finally, we express the IMPS and IMVS transfer functions in terms of the capacitive and resistive features of a general equivalent circuit of IS for the case of a photoanode used for solar fuel production. We critically discuss how much knowledge can be extracted from the combined use of those three techniques.
View details for DOI 10.1021/acs.jpclett.6b02714
View details for Web of Science ID 000391653200027
View details for PubMedID 27958744
Understanding the synergistic effect of WO3-BiVO4 heterostructures by impedance spectroscopy
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2016; 18 (13): 9255-9261
WO3-BiVO4 n-n heterostructures have demonstrated remarkable performance in photoelectrochemical water splitting due to the synergistic effect between the individual components. Although the enhanced functional capabilities of this system have been widely reported, in-depth mechanistic studies explaining the carrier dynamics of this heterostructure are limited. The main goal is to provide rational design strategies for further optimization as well as to extend these strategies to different candidate systems for solar fuel production. In the present study, we perform systematic optoelectronic and photoelectrochemical characterization to understand the carrier dynamics of the system and develop a simple physical model to highlight the importance of the selective contacts to minimize bulk recombination in this heterostructure. Our results collectively indicate that while BiVO4 is responsible for the enhanced optical properties, WO3 controls the transport properties of the heterostructured WO3-BiVO4 system, leading to reduced bulk recombination.
View details for DOI 10.1039/c5cp07905e
View details for Web of Science ID 000373000100052