Dr Alan Bowman

Abstract:

This dataset accompanies the publication "Re-defining non-tracking solar cell efficiency limits with directional spectral filters" published in ACS Photonics (10.1021/acsphotonics.4c02181). The data can be used to reproduce figures 2-4 in the main text and all plots with data in the supporting information (noting figure 1 in the main text is only schematics). All data was generated via home-built modelling codes. All files are in .CSV and easily readable. The abstract for the associated paper is as follows: Optical filters that respond to the wavelength and direction of incident light can be used to increase the efficiency of tracking solar cells. However, as tracking solar cells are more expensive to install and maintain, it is likely that non-tracking solar cells will remain the main product of the (terrestrial) solar cell industry.  Here we demonstrate that wavelength and directionally selective filters can also be used to increase the efficiency limit of non-tracking solar cells at the equator beyond what is currently understood by up to ~ 0.5 % (relative ~ 1.8 %). We also reveal that such filters can be used to regulate the energy output of solar cells throughout a day or year, and can reduce the thickness of the absorber layer by up to 40 %. We anticipate that similar gains would be seen at other latitudes. As this filter has complex wavelength-direction functionality, we present a proof-of-concept design based on Luneburg lenses, demonstrating these filters can be realized. Our results will enable solar cells with higher efficiency and more stable output while using less material.LNETv

Abstract:

Exploring nonequilibrium hot carriers from plasmonic metal nanostructures is a dynamic field in optoelectronics, with applications including photochemical reactions for solar fuel generation. The hot carrier injection mechanism and the reaction rate are highly impacted by the metal/molecule interaction. However, determining the primary type of reaction and thus the injection mechanism of hot carriers has remained elusive. In this work, we reveal an electron injection mechanism deviating from a purely outer-sphere process for the reduction of ferricyanide redox molecule in a gold/p-type gallium nitride (Au/p-GaN) photocathode system. Combining our experimental approach with ab initio simulations, we discovered that an efficient inner-sphere transfer of low-energy electrons leads to an enhancement in the photocathode device performance in the interband regime. These findings provide important mechanistic insights, showing our methodology as a powerful tool for analyzing and engineering hot-carrier-driven processes in plasmonic photocatalytic systems and optoelectronic devices.LNE

Abstract:

Evidence from cross-sectional electron microscopy has previously shown that Se passivates defects in CdSexTe1−x solar cells, and that this is the reason for better lifetimes and voltages in these devices. Here, we utilise spatially resolved photoluminescence measurements of CdSexTe1−x thin films on glass to directly study the effects of Se on carrier recombination in the material, isolated from the impact of conductive interfaces and without the need to prepare cross-sections through the samples. We find further evidence to support Se passivation of grain boundaries, but also identify an increase in below-bandgap photoluminescence that indicates the presence of Se-enhanced defects in grain interiors. Our results show that whilst Se treatment, in tandem with Cl passivation, does increase radiative efficiencies in CdSexTe1−x, it simultaneously increases the defect content within the grain interiors. This suggests that although it is beneficial overall, Se incorporation will still limit the maximum attainable optoelectronic properties of CdSexTe1−x thin films.LNE

Abstract:

The fraction of light absorbed in a material is a key parameter for a wide range of optoelectronic and energy devices, including solar cells, light emitting diodes, and photo(electro)chemical devices. It can reveal detailed performance information and establish a material’s theoretical efficiency limits. However, measuring absorption accurately is challenging, especially due to scattering effects at the macroscale and achieving perpendicular illumination over a small area at the microscale. In this tutorial, we present concepts and best practices in measuring absorption at both the macro- and micro-scale. We also give examples of using absorption to reveal critical optoelectronic information in energy devices. This work aims at standardizing the recording of absorption measurements across a number of fields, allowing for improved microscale understanding of a wide range of samples.

Abstract:

<p>This dataset accompanies the publication "Quantum-mechanical effects in photoluminescence from thin crystalline gold films" published in Light: Science & Applications (https://doi.org/10.1038/s41377-024-01408-2). The data can be used to reproduce plots 1-4 in the main text and all plots with data in the supporting information. This data was generated through a combination of raman spectroscopy, microscale absorption meaurements and density functional theory modelling. All files are in excel spreadsheets and easily readable, except compressed files which have a readme file in the appropriate section.</p> <p>The abstract for the associated paper is as follows:</p> <p>Luminescence constitutes a unique source of insight into hot carrier processes in metals, including those in plasmonic nanostructures used for sensing and energy applications. However, being weak in nature, metal luminescence remains poorly understood, its microscopic origin strongly debated, and its potential for unravelling nanoscale carrier dynamics largely unexploited. Here, we reveal quantum-mechanical effects emanating in the luminescence from thin monocrystalline gold flakes. Specifically, we present experimental evidence, supported by first-principles simulations, to demonstrate its photoluminescence origin (i.e., radiative emission from electron/hole recombination) when exciting in the interband regime. Our model allows us to identify changes to the measured gold luminescence due to quantum-mechanical effects as the gold film thickness is reduced. Excitingly, such effects are observable in the luminescence signal from flakes up to 40 nm in thickness, associated with the out-of-plane discreteness of the electronic band structure near the Fermi level. We qualitatively reproduce the observations with first-principles modelling, thus establishing a unified description of luminescence in gold monocrystalline flakes and enabling its widespread application as a probe of carrier dynamics and light-matter interactions in this material. Our study paves the way for future explorations of hot carriers and charge-transfer dynamics in a multitude of material systems. </p&gt