Imperial Materials

Dr Andrew Cairns is a Research Fellow in the Department of Materials. He is also a part of the LGBTQ+ community and Mental Health First Aider. To mark the end of Pride 2021, Dr Cairns shares more about his current research, his motivations for studying Materials Science and the importance of having an LGBTQ+ role model in STEM.

Hi, I’m Andrew, and I’m a Research Fellow in the Department of Materials. To give you an overview of my research: I investigate materials that behave in the opposite way than you might expect: so, instead of expanding when heated, they shrink. Even more bizarrely, under pressure, they expand rather than compressing in every direction.

We have found examples of these behaviours that are very extreme in a class of materials called molecular frameworks. We continue to look for larger and even more unusual properties and link properties together to engineer multi-functional materials. The challenge that drives me is how to manipulate matter — atom by atom — to realise advanced functionality.

Motivating this work further is the impact such unusual materials could have on future technologies. These properties — today mostly seen as curiosities — could enable more sensitive touch screens, devices with variable-pressure recognition, more accurate sensors, or more efficient data storage. We aim for a step-change in device performance that will only be possible with radically different materials than those currently used. So, alongside making new materials, we are working to fabricate these materials into prototype forms (like very thin coatings) that could be integrated into devices.

‘Science is AMAZING’

Like most of us in science, there is huge joy when you discover something no one else has ever seen before. During my doctoral studies, I remember the first time this happened: my supervisor and I were staring at an Excel workbook, systematically inputting numbers as the machine outputted data, and not believing our eyes. We worked in almost silence until we went to lunch and could say, ‘is it true?… This is amazing!’ Who knew an Excel file would ever be that interesting?

Of course, not every day is eureka-central: it takes a lot of patience and many failed experiments to get to that point. In those times, the things I enjoy most are the people and amazing facilities I am very fortunate to work with. I worked previously at the European Synchrotron Radiation Facility (ESRF), one of the most intense sources of X-rays in the world. I was blown away by the dedication of the scientists there and the ingenuity of the engineers who keep such a massive machine working (it has a circumference of over 800 m). Today, I continue to work with groups close to home, such as the Henry Royce Institute and all around the world. Getting involved in projects and seeing ideas develop with others is rewarding every day, including supporting students and colleagues to achieve great results.

The importance of LGBTQ+ role models in STEM

I was extremely fortunate that my doctoral supervisor, Prof Andrew Goodwin, is one of only a few LGBT+ academics in STEM. I was not aware of this when I first met him, but I am sure that having this role model has changed my experience in science. On one level, having someone to look up to gives confidence that my sexuality shouldn’t hold me back. This makes it easier each time I have to come out in a professional context. On another, I know that if ever I did experience hostility (I am fortunate this has never happened), I have a large group of supporters who would make it clear that such behaviour was not acceptable. There is huge power in knowing you are not alone.

Bringing your whole self to work is something I feel is so important in a job like being an academic for LGBT+ scientists or any other underrepresented group. We are often working 1:1 with collaborators, students and colleagues to support one another where trust and openness are key. Having been supported in my own journey makes me absolutely committed to doing my best for those around me.

I am therefore passionate about doing great science but working to make academia more welcoming and diverse. To me, these are one in the same: if we treated our equipment badly, we would expect bad data and therefore bad science, so why expect anything different from our people? More broadly, why does academia shelter, and in some cases celebrate, harassers and bullies? All our efforts in equality, diversity, and inclusion should be celebrated as a central part of being a scientist. And I continue to learn: to do my best science and to be the best scientist I can be. I am sure I will make mistakes in both areas, but I never want to lose the desire to do the right thing.

My advice for the next generation of LGBTQ+ Scientists and Engineers

Find your champion! I was lucky this was someone who I was interacting with every day, but there are more and more visible LGBT+ scientists and engineers out there who want to support the next generation. It might be that you are comfortable to come out and share your experiences with these people, to find that community, and that is great. Or it might be that you are less comfortable, and so even just checking the Twitter account of an LGBT+ scientist or engineer you admire can help give you a sense of connection.

We also must recognise how different parts of our community have different challenges, and others may live in countries where it is simply not possible to be out. Everyone has a responsibility to respect difference, acknowledge privilege and educate ourselves. In particular, current attacks on the trans* community are deeply worrying, reminding us all that rights that may seem to be won can be taken away just as easily. If you can, fly the flag and celebrate – but remember Pride is still a protest, and there is work to be done.

Read Dr Andrew Cairns on his research and LGBTQ+ role models in STEM in full

What we’ve learned through the WE Innovate scheme

As academic researchers, the prospect of dipping your toes into the world of business can be a terrifying prospect. But the higher up the ladder you climb the more it becomes clear just how interdependent two streams of academia and business really are. The whole landscape can be quite tricky to navigate but luckily, Imperial has a few different programmes to help researchers get off the ground and learn about what it takes to translate an idea from the lab to the boardroom.

Read Meet the team: Zyme Biosciences reach WE Innovate finals in full

Dr Robert Hoye is a lecturer in the Department of Materials. In this post, he explains the potential for halide perovskites and their derivatives in renewable energy. Dr Hoye recently led one of the key roadmaps for the Henry Royce Institute, identifying halide perovskites as one of the key technologies for the UK to achieve carbon neutrality by 2050. 

Photovoltaics produce clean electricity from sunlight and are one of the leading renewable technologies. As such, it is vital to accelerate the deployment of this technology. However, realising a high electrification future will require the number of photovoltaic devices installed every year to increase by over an order of magnitude. A rapid expansion in the manufacturing of photovoltaics is needed, and this may be fulfilled by a newcomer to the photovoltaics scene: halide perovskites.

What are halide perovskites?

The term ‘perovskite’ refers to a family of materials with the crystal structure shown in Figure 1. The prototypical perovskite (calcium titanate) was found nearly 200 years ago in the Ural mountains by Gustav Rose, who named the material after Lev Perovskiy. Other perovskites include barium titanate, strontium titanate, lead titanate, and others, and these materials have been used in ferroelectrics, piezoelectrics and pyroelectrics. It was only recently that halide perovskites have come to prominence for photovoltaics.

In 2009, Tsutomu Miyasaka and colleagues reported methylammonium lead iodide as a sensitizer in liquid-junction solar cells, demonstrating a power conversion efficiency of 3.8%. In subsequent years, a series of developments transformed this material from yet another novel solar absorber to the dominant next-generation photovoltaic technology. In 2020, the certified record efficiency of perovskite solar cells reached 25.5%, which is already on the cusp of matching the record performance of solar cells based on single-crystalline silicon (26.7%), the dominant commercial technology. Remarkably, whilst crystalline silicon required 6 decades of development, halide perovskites have only been developed for one decade. Furthermore, halide perovskites hold several critical advantages over crystalline silicon:

1. Halide perovskites can be grown at significantly lower temperatures, with the absorber typically processed at only ~100 °C. This reduces the carbon footprint of perovskite solar cells, as well as the energy and cost required for its production;

2. Halide perovskites have significant chemical versatility, with the bandgap tunable over the entire visible wavelength range by controlling the composition or dimensionality.

An important implication of these factors is that perovskite solar cells can be used to produce ‘tandem’ photovoltaics with silicon solar cells (Figure 2). Much like tandem bicycles, tandem photovoltaics electrically couple together two solar cells (in this case perovskites and silicon) to work together to generate more power. Such devices can exceed the efficiency limit of each device working individually. Critically, by adding a perovskite solar cell over a silicon solar cell, increases inefficiencies can be achieved without significantly adding to the total cost, thus reducing the ratio of the cost of the solar cell compared to the total power produced, such that photovoltaics become more cost-competitive against fossil fuels.

How perovskites photovoltaics be pushed from lab to market?

Halide perovskite solar cells have risen in efficiency faster than any other photovoltaic technology and are already at the level at which they can be commercialised. However, their fast rise has also meant that most research on this technology has been performed at the lab scale, in which the most efficient solar cells have device areas smaller than a fingernail. By contrast, manufacturing perovskite photovoltaics at the level needed to make an impact on climate change will require at least several million square metres of devices per year. Achieving this will require fabricating with speed and at scale. Perovskites can be grown over a large area by printing, spraying or evaporating, but it is critical that these techniques can grow devices rapidly in order to maximise the number of devices produced per manufacturing hour and therefore reduce the overall costs.

Another critical concern is the operating lifetime of the devices. The original perovskite composition, methylammonium lead iodide, is thermodynamically unstable and degrades in ambient air within days. There has been substantial work on developing alternative compositions, as well as passivating materials at surfaces, with improved stability in air containing moisture. Through these efforts, and coupled with encapsulation, devices stable for longer than a year have been demonstrated, and modules that pass industry-standard stability tests have been achieved. However, the stability tests were developed for silicon solar cells, and the degradation modes in perovskites can be substantially different. It will therefore be critical to developing accelerated degradation tests specifically for perovskites, and the field data that is starting to be collected will be valuable in this effort.

How can we systematically find lead-free alternatives to the perovskites?

Beyond the scale-up and stability challenges, halide perovskites are also limited by the presence of lead, which is toxic and regulated in many jurisdictions worldwide. Currently, outdoor photovoltaics are exempt from European lead regulations, and there is debate over the extent to which the lead content of halide perovskites could limit its adoption worldwide. Nevertheless, the astonishing rise of halide perovskites has posed the critical question of how such performance could be replicated in alternative materials.

The search for these lead-free alternatives has mostly proceeded in the same way solar absorbers were identified before lead-halide perovskites were found, that is by trial-and-error. Not only does this have a low success rate, there are also too many materials to systematically explore without encountering false negatives or positives.

A more systematic approach that has been adopted is to identify materials that could replicate the defect tolerance of halide perovskites. Developing defect-tolerant semiconductors is the opposite approach to traditional semiconductor engineering. Historically, the approach taken has been to grow semiconductors to minimise the density of defects, which usually involves high temperature, slow and expensive growth methods. What the lead-halide perovskites have shown is how materials can be efficient without being defect-free if most defects have energy levels close to the band-edges and have limited ability to capture electrons or holes. Thus, although halide perovskites have millions of times more defects than silicon, they have comparable performance in photovoltaic devices.

A proposition is that the defect tolerance of halide perovskites comes about from its electronic structure. This has prompted efforts to find materials that are electronically analogous. Many of the materials identified are bismuth-based compounds, such as bismuth oxyiodide. This is because bismuth is next to lead on the periodic table (Figure 3), but has no evidence for toxicity, and is used in over-the-counter stomach medicine. Such materials are termed ‘perovskite-inspired materials’. Thus far, there have been a handful of materials found to demonstrate similar defect tolerance to the halide perovskites. But the understanding of what gives rise to defect tolerance is only now emerging and is an active area of research.

What else can we use the new perovskites and derivatives for?

Demonstrating a new material in efficient photovoltaics opens up many possibilities for applying the material in a broad range of alternative applications. One such application is for indoor light harvesting. These energy-havesting devices are needed to power low-cost, low-power electronic devices that can communicate with each other via the Internet – such as a mobile phone. This ecosystem of devices is termed the ‘Internet of Things’ (IoT), which is giving rise to infrastructure (e.g., houses, cities, hospitals) that are responsive to the users. Currently, most IoT devices are powered by batteries, which only have a limited lifetime. Given that there are over tens of billions of IoT devices worldwide, millions of batteries need to be recycled daily, creating substantial waste. This sustainability challenge will only increase in the future as the IoT ecosystem exponentially grows in size.

To solve this challenge, photovoltaics can be embedded into each IoT device to harvest energy from light to recharge the energy storage device (which could be a capacitor or a rechargeable battery) that then powers the IoT device in the dark. Currently, the standard indoor photovoltaic material is hydrogenated amorphous silicon, but the photovoltaic efficiencies are below 10% under indoor lighting. Halide perovskites have already demonstrated 37% efficiency indoors, which increases the power harvested from the microwatt range to the milliwatt range.

However, lead may be less tolerated in consumer or healthcare products than for outdoor photovoltaics. Recent work into lead-free perovskite-inspired materials for indoor photovoltaics, and optical analyses has shown that devices made from these materials could match or exceed the performance of halide perovskites indoors, and deliver high efficiencies with non-toxic materials that can be manufactured through low-toxicity processes. Beyond indoor light-harvesting, halide perovskites and perovskite-inspired materials can be used to harvest sunlight to split water and CO2 to produce clean fuels, or to more effectively detect X-rays, and therefore be used to make safer medical detectors.

 

Further reading

C. A. R. Perini, T. A. S. Doherty, S. D. Stranks,* J.-P. C.-B.,* R. L. Z. Hoye.* Pressing Challenges in Halide Perovskite Photovoltaics – From the Atomic to Module Level. Joule, 2021, 5, In Press. DOI: 10.1016/j.joule.2021.03.011

R. L. Z. Hoye,* J. Hidalgo, R. A. Jagt, J.-P. Correa-Baena, T. Fix,* J. L. MacManus-Driscoll.* The Role of Dimensionality on the Optoelectronic Properties of Oxide and Halide Perovskites, and their Halide Derivatives. Advanced Energy Materials, 2021, 2100499, Early View. DOI: 10.1002/aenm.202100499.

Read Research Insights: Interview with Dr Robert Hoye in full

During Autumn Term 2020, our first-year students in the Department of Materials started using lab-in-a-box projects to support their learning from home. These projects are used as a bridge between in-person teaching, while our students are learning remotely due to the pandemic. Two of our students have shared their experiences using the lab-in-a-box projects and what they’ve learned.

Anjali Devadasan

The lab in the box was an incredibly exciting aspect of the first few weeks of term. The doorbell rang, I collected the parcel and immediately opened the box to explore the contents inside. The most discussed object on the year group chat (after the vernier callipers of course) was the mini microscope. We shared images of objects under the microscope and guessed what the objects examined were, which ranged from oranges, leaves, paper, and even phone screens.

Remote learning has resulted in spending most of our time in front of laptop/computer screens, but the lab in a box has provided us with a change of scenario on many Friday afternoons. The first time I used something from the box was in the Design Study drawing lesson where our task was to sketch a couple of 3D printed parts. Little did we know that the same parts would help us measure density with Arduino in the near future! Arduino sessions began with a short lecture describing the task for the day and for the next three or four hours, I would work through PDF instructions alongside my design study company and the much-appreciated help from our GTA, Harry. We guided each other, laughed at our mistakes, and were confused together and I think the challenges really brought our company together as a team.

Once we gained enough experience with Arduino, we did some lab work in company sub-groups of four. Labs consisted of the various subgroups measuring electrical and thermal conductivity and density using the Arduino setups we had learned. We also did hardness testing for different samples – where we used our mini microscopes! I enjoyed learning the Arduino together as it was fulfilling when we solved the problems with the setup and managed to get it working to receive some real values.

My favourite set up was the very first time we managed to display temperature readings on the little LCD screen. It was exciting when realistic temperatures for room temperature would appear or when they would change if we put different objects near the sensor, such as ice. It will be interesting to use this set up for the upcoming polymer labs.

https://vimeo.com/509725064

 

Amélie Mattheus

I thought that the lab in a box project was a very creative idea. Picking up my lab box allowed me to see my peers for the first time. Even though it was socially distanced and completely COVID safe, it was nice to put a face to the names I had been seeing on Teams. When arriving back in my accommodation, I was very excited to open the box, it was like receiving a surprise delivery.

The box contained several recognisable objects which made me feel relieved at first, however, there were objects that I had never seen before. The Arduino lab was something completely new to me. Hence it was very exciting to see my LED light turn on after completing the lab. There were some struggles with the following Arduino labs due to technical constraints like the wires not being soldered hence not being able to get a connection. The meeting allowed me to see examples of other people’s work that did work. It was nice to be in smaller groups as you can talk more freely.

The GTA was very helpful and helped us through some long labs. He was always prepared to answer our questions when we got stuck. We also had a hardness lab, where they provided us with a spring, materials to test, and a tube. The hardness lab was the lab I enjoyed the most because it was directly related to materials and one of the properties that we had previously learned about. The goal was to indent the material and measure the radius of the indent. We were provided with a microscope that allowed us to measure even the smallest indents on rubber, which tends to go back to its original shape. In addition, due to doing the labs at home, you are able to use the equipment outside of class as well, for example, one of my group mates pointed out that with the microscope you were able to see the pixels on your laptop screen.

In the end, we were given some extra data due to the constraints of doing it at home. However, the given data allowed us to still analyse the data and use the software available for that. I enjoyed the labs at home, especially because I was still able to discuss and compare my results with those of others. I thought it was a creative alternative that allowed us to still do labs and achieve the skills learned by doing these.  

Read Materials Science from home: First year students share more about their lab-in-a-box projects in full

Many Undergraduate students in the Department of Materials will choose to undertake an Undergraduate Research Opportunity Programme. Sometimes the research can lead to co-authorships with the academic group.

This was the case for second-year Undergraduate student Yingxu Li and fourth-year Undergraduate student Seif Mehanna, whose research contributed to a recent paper with Dr Mark Oxborrow, now published in Physical Review Applied. The paper demonstrates how a cheap organic material can be exploited to detect extremely weak radio signals so weak that the signal contains only a small number of radio-frequency photons.

Both students have provided us with a snapshot of the research they did for the paper and their UROP experience.

Seif Mehanna

My part of the research aimed to see if we could get a maser to run using a much cheaper and less bulky light source than a massive medical laser. Lasers tend to be very inefficient at producing yellow light, so we used a luminescent concentrator instead. Luminescent concentrators are devices that concentrate and shift the colour of light, so you end up with a very bright light with the desired wavelength (colour).

I made this very simple setup where we had a luminescent concentrator that Dr Oxborrow had made earlier, surrounded it with two Soviet-made Xe-flash lamps held up with lab clamps, and had a sample at the end of the concentrator that we tried to get to mase. As old as those lamps were, they’re very energy efficient and did a great job! They were so powerful that you could feel when they went off, just like with the flash in a professional studio. Sometimes you don’t need the newest and fanciest equipment to be on the cutting edge of science!

I’m pleased to see the consequences of my research included in this paper, and I hope that it shows that you can have fun and look to the past while doing pioneering research to advance the future.

Yingxu Li

My research contribution to the paper was to render the instrument setup of this newly-developed MASTER, trying to make it look real as in reality. Figures 5(a) and (b) in the publication were produced by the 3-D rendering program, “Blender”.

This UROP was the first-ever research experience in my life, definitely unforgettable! Although the whole programme shifted to online-based, I learned a lot about MASER and 3D graphical modelling using Blender software. Also, the working vibe in Dr Mark Oxborrow’s team was so welcoming, and everyone in the team was happy to help me as “a baby in scientific research”. It gave me an immersive insight into researchers’ lives and a taste of how a publication paper was produced. Last but not least, thank you to Dr Oxborrow for allowing me to contribute to the paper. It made the summer of 2020 so special!

I hope this can show the fantastic opportunities available to students in our department.

Hear more from our students about their UROPs and find out how to apply.

Read Student Interviews: We co-authored a paper using research from our UROP in full

To celebrate LGBT STEM Day 2020, Dr Ben Britton, Reader in Metallurgy and Microscopy – and RAEng Research Fellow, has shared more about LGBT+ STEM Day, his research and how simple acts from everyone can go a long way.

Can you tell us more about yourself and your research?

Hi, I’m Ben and my pronouns are he/him. I’m a Reader in Metallurgy and Microscopy, and I lead a group who try to understand how metals are processed, perform and ultimately fail in high-risk high-value applications, such as nuclear power plants, aeroengines, and the petrochemical industry. We work together to combine experiments and simulations together, collaborating with folks across Imperial, in industry and across the world. I also tweet a bit (@bmatb), teach a bit, and have other interests.

What does LGBTSTEMDay mean to you and why is it important for everyone?

I am not only a material scientist and engineer, I’m also a gay man. Many folks may suggest that my sexuality and gender identity have no relevance for my work. This is incorrect, as numerous surveys and academic papers tell a different story. There is substantive co-correlation of evidence that the relationships we form and who we connect with influence our successes in work and beyond. LGBTSTEMDay provides people who identify as ‘not straight’ and/or ‘not cisgendered’ (i.e. those whose current gender identity matches their gender identity at birth) to celebrate contributions of those people like us, create communities, and create meaningful changes to the practice of science, technology, engineering and maths across the world.

On a more personal level, I also used #LGBTSTEMDay to ‘come out’ more widely in public. As frankly, it is EXHAUSTING to hide this part of your identity and to worry about the implications on your career. So #LGBTSTEMDay has, as I shared in a public talk at the College, entitled me to say: go and read my blog piece – ‘So it’s #LGBTSTEMDay…so what?’

Who are your greatest role models in STEM?

This is always a challenge. Most historical queer figures have had their queer identity written out of the history books. Additionally, one of the privileges for me, as a white man in STEM, is that there are many people like me who have ‘succeeded’ and can be seen in positions of power. This also highlights the imbalance in our midst, especially for those who are at the intersection of minority identities and are doubly marginalised (e.g. people who identify as Black and queer).

There are efforts to correct this, as, for instance, Dr Jess Wade (and many others) have been strengthening the representation of individuals from marginalised groups on Wikipedia, and so we can now more easily identify and empathise with existing role models in our field. There are also professional networks, such as IOM3Pride, LGBTQ+ STEM, Pride in STEM, 500 Queer Scientists and many more where LGBTQ+ people can find people like them, share experiences, and benefit from networking opportunities that they have been (directly and indirectly) excluded from.

How can everyone be an ally and action for change?

I want co-conspirators who are willing to say that the status quo is not good enough, and to agitate for change. There is no reason why we should sustain and support systems that establish marginalisation of individuals based upon their sexual orientation and gender identity, as well as other protected characteristics (and socio-economic class).

There are old and new barriers that actively exclude LGBT+ people and members of other minority groups from participating, and these exist both within the Department, within the College, in the Profession and in wider society. Dismantling these all at once is a daunting task, but simple acts can go a long way, and lots of the work to identify these issues has been done already. So if you want a more refined list of recommendations, you should read the Royal Society of Chemistry, Institute of Physics and Royal Astronomical Society report on Exploring the Workplace Climate for LGBT+ Physical Scientists. 

Read LGBTSTEMDay: Interview with Dr Ben Britton in full