Left Brain

Left lateralisation is typically associated with logic, language, numbers, and analytical thinking.
As such this page is dedicated to the scientific projects I have worked on.

Selectively reflective coatings

Antireflective coatings are used to increase the yeild of solar cells by preventing reflection as a loss mechanism, instead causing the light to enter the cell and to be converted to electricity.
However the Sun's spectrum contains a range of energies, including the infrared, the portion of electromagnetic radiation that causes heating. Unfortunately, heating in solar cells causes a reduction in open-circuit voltage and in turn the cells power conversion efficiency.

This project, funded by a Loughborough enterprise grant, further developed a coating that can be applied to solar module cover glass to simultaneously be antireflective to visible light, and reflective to infrared. This will not only boost the performance of cells, but maintain a higher performance throughout the day, doubly improving energy yeild.

As a Research Associate my role was to investigate how the optical properties of one of the transparent layers varied with composition, which I carried out using the combinatorial methodology I developed in my PhD.
For my involvement I was listed as a co-inventor on the subsequent patent application.

Earth-abundant photovoltaic materials

My PhD research covered a range of specific topics, but can be summarised as the development of semiconductors with optoelectronic properties suitable for photovoltaic energy generation, aiming specifcally for compounds made from elements abundant in the Earth's crust.
The advantage of this is the intrinsically low cost of resources for producing the compounds, contributing to a lower module cost and ultimately helping to lower cost as a barrier to entry for the end user.

Though the justification for my area is economical, my personal research is highly empirical around materials processing, characterisation, and discovery. My work chapters demonstrate original contributions for three seperate but related compounds:

  • Cu2ZnSnSe4 - The kesterite CZTSe is widely touted as the key to tera-watt scale deplyment of PV. My first work chapter investigates a new solvent system for solution processing CZTSe, allowing spray pyrolysis as a low-cost and high-throughput deposition technique.
  • Cu2ZnZrSe4 - Despite a huge collective effort, all flavours of kesterite have stalled in terms of demonstrated record lab efficiency. My second work chapter hypothesises why there is such a large performance gap between kesterites and it better-performing material cousins, and attempts to test this hypothesis by synthesising for the first time the 'kesterite' system CZZrSe.
  • Cu:ZnSe - While investigating CZZrSe a much simpler compound presented itself with ideal optoelectronic properties for photovoltaics. My third work chapter is an exploratory investigation into the semi-binary compound Cu-doped ZnSe.

My thesis is pending viva voce, and will be available from the Loughborough Repository on final submission.

Publications

How do you solve a problem like the Voc-deficit in kesterites?
(In progress), 2020

This work will be the key features from the tightly intertwined second and third work chapters of my thesis. The paper not only proposes a tangible source for the much sought-after Voc-deficit in kesterites, but proposes two research paths to circumvent the material flaw, each with promising preliminary work.

Understanding the role of selenium in defect passivation for highly efficient selenium-alloyed cadmium telluride solar cells
Nature Energy, 2019

This work is a collaboration with my friend and colleague T.A.M. Fiducia. By overlapping exactly a seris of optoelectronic and compositional characterisation tehcniques, Fiducia could look for correlations between selenium concentration and defect assivation. The measurements that he collected generated an area of more than 27,000 data points, and so I joined as a collaborator to handle and process the data, for extraction of meaningful conclusions from the large data set.

Water based spray pyrolysis of metal-oxide solutions for Cu2ZnSn(S,Se)4 solar cells using low toxicity amine/thiol complexants
Thin Solid Films, 2018

This work is the contents of my first thesis work chapter, describing the then-record efficiency device produced for CZTSe solar cells within our group, using the novel water-based solvent system I developed.

Research internship

During the summer before my final undergraduate year I was granted a bursury to work in the Physics department as an intern under Dr Kelly Morrison. I helped with setting up and testing the calibration standard that would be the basis of KM's later research into the Spin Seebeck Effect, gained a working knowledge of cryostat systems, vacuum pumps, and ultra-high vacuum systems for thin film deposition, and learned the basics of the programming language LabVIEW.

For a short writeup of my time, I produced a seris of accurate graphics displaying the callibration standard. This internship was also the point I decided I wanted a career in research, and as such am deeply grateful to KM for taking me on.

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Copyright © 2020 Lewis D. Wright.