Enhancement of low-cost organic solar cells by plasmonic structures for application and manufacturing in developing countries
Today’s major source of energy (85%) – fossil fuel – is depleting rapidly and leads to major environmental problems including global warming. The Paris Agreement (COP21) in December 2015 has stressed the need to accelerate the low-carbon transformation of the global economy. The proposed solution is the transition to sustainable, renewable sources such as water, wind and sun. With 120,000 TW of solar power impinging on earth (with a practical extractable power of 600 TW), just 0.02% of the sun’s energy reaching our planet is sufficient to cover the annual energy demand of mankind. Yet, solar energy delivers only 0.1-0.2 % of the world energy consumption. This calls for affordable, clean energy research, development and deployment activities in the materials, engineering and system design in the field of solar cells so that modern energy services can be made accessible to remote areas of developing and less developed countries such as Brazil, Ethiopia and beyond.
Solar cells work by absorbing the incident solar light and converting it into positive and negative charges which are then collected at the respective electrodes. In silicon solar cells, the indirect bandgap requires thick active layers to compensate for its poor absorption. However, organic and hybrid perovskites have large absorption coefficients and require only 100-200 nm thickness. Their solution method of preparation and low temperature fabrication route requires only low energy input with energy payback time (EPBT) as low as 3 months, whereas the silicon based solar cell EPBT is as high as seven years. Thus, organic photovoltaics (OPVs) and hybrid perovskites are a promising choice for the solar energy harvesters for developing countries. Despite these promising attributes, the thin active layer of organic solar cells is not enough to absorb all the incident solar light. In this project, we are exploring how to enhance the absorption of light in organic/hybrid perovskite solar cells using plasmonic structures and by light diffracting nanostructures with collaborators in Brazil and Ethiopia. Through this approach, power conversion efficiency will be enhanced even with a reduced amount of active layer material. This opens up new application realms for organic solar cells such as a portable mobile phone charger, solar powered bags, tents topped with flexible solar cells which can increase the lighting and communication facility in remote areas of developing countries. In less developed countries like Ethiopia where the population is growing at 2.6 % annually and 80% of the population resides in rural areas, the extent of mobile phone ownership (24.7%) is higher than the fraction of households connected to the electrical grid (4.8%). Portable, flexible OPVs and hybrid solar cells can be an effective solution to this growing demand of off-grid power for lighting and telecom applications.
Organic Semiconductor Optoelectronics
Organic Solar Cells
Measurement of wavelength using laser speckle
Light is a wave and it is well known waves can interfere creating patterns with constructive (bright) and destructive (dark) regions. For a laser this means we can create a granular pattern – a speckle pattern- that is rich in information about the incoming waves. We show how we can use this pattern from a laser as a signature to measure the laser wavelength to high accuracy and use it to remove laser fluctuations and thus stabilise a laser. This has applications for laser measurement, spectroscopy and stabilising lasers for quantum applications.
With the increasing availability of smartphones, we sought to investigate whether:
- an app could be deployed with smokers intending to quit
- knowledge of craving and smoking behaviour helps smokers quit
Approximately 11,000 people die in Scotland each year from smoking related causes. While quitting smoking is relatively easy, maintaining a quit attempt is very difficult. Pharmaceutical treatments improve abstinence rates, however they do not address the spatial aspects of smoking behaviour.
Since smartphones can log spatial, as well as quantitative and qualitative data related to smoking behaviour, we can support smokers by first understanding their smoking behaviour and then sending dynamic support messages post-quit.
Dr Robert Schick
Dr Tom Kelsey
An array of 16 finished horns for airport security imaging radar
High performance, low cost, antennas in the microwave to THz regime
Horn antennas at microwave, mm-wave and terahertz frequencies are commonly used in high performance radars, radiometers and in advanced instrumentation and communication systems. Increasingly, these applications require highly directional, strongly polarised beams to be produced by very compact, low weight antennas, especially for spaceborne use.
In this project, we are developing a generic design tool which provides a simple and flexible methodology to design compact horns with very high levels of performance (e.g. low sidelobe level, low cross-polar level over wide bandwidths) at low cost. We have developed and tested a number of high performance designs, we are exploring novel low cost manufacturing methods, and we are working with manufacturers and microwave component suppliers targeting a number of application areas, including upcoming space missions.
Measured near field scans of the beam from the submillimeter wave split block feedhorns, co-polarised (left)
and cross-polarised (right)
The robotic arm mimics the movement of the volunteer, detected via the muscle contraction sensor.
Wearable organic optoelectronic muscle contraction sensor
Wearable sensors are desirable for a wide range of medical applications including long-term continuous health monitoring and various robotic tools based on human-machine interactions. Ideally, wearable sensors should be light-weight, compact, flexible, non-invasive, easy to fabricate and low cost. Our work in organic optoelectronic devices suggests a new class of wearable sensors for medicine and sports. A flexible, non-invasive organic optoelectronic device is demonstrated which can be worn on the body to measure signals from muscles and control artificial limbs.
Organic optoelectronic devices exhibit attractive properties of tuneable light emission, easy fabrication on arbitrary, even flexible and stretchable, substrates, and the ability to generate and detect light. We have shown that the combination of organic light-emitting diodes (OLEDs) and organic photodiodes (OPDs) enables compact, non-invasive, flexible sensors for medical applications by simple solution-processing methods. Specifically, we developed a potentially low-cost muscle contraction sensor that can measure signals from intact muscles to control the movement of active prosthetic devices such as artificial limbs. Moreover, we demonstrated the feasibility of this all-organic, optoelectronic sensor by controlling a robotic arm so that it mimicked the motion of a healthy volunteer’s arm for two types of muscle contractions. The sensor measures the amount of light scattered by the skeletal muscle tissue along and parallel to the muscle fibre and can distinguish between isometric (i.e. muscle length remains constant) and isotonic (i.e. the muscle length changes, at a constant exerted force) contractions. Due to the ability to distinguish between different types of contractions, in addition to its non-invasive character and insensitivity to electromagnetic noise, the OLED and OPD based optical sensor is a promising alternative to the surface electromyography technique currently employed to detect the signals from muscles.
NOMAD (NMR Online Management and Datastore)
NMR (nuclear magnetic resonance) spectroscopy is most frequently used by chemists and biochemists to investigate the properties of organic molecules. The impact of this technique on the science has been substantial because of the range of information and the diversity of samples that can be analysed.
NOMAD (NMR Online Management and Datastore) is a cloud computing system developed through collaboration between the Schools of Chemistry and Computer Science at the University of St Andrews and has been funded through the EPSRC IAA funding. This system automates and simplifies a number of key workflows in NMR lab management, data acquisition and access which became recently a bottleneck for NMR data production.
Our recent development has been focused on interfacing NOMAD database with PURE (Research information system) in order to facilitate Open Access deposition of NMR data underpinning research at the School of Chemistry. Furthermore, the system architecture has been redone in order to make the transition from prototype (version 1.2 currently serving at the NMR facility at the University) to a market-ready product (version 2.0) that could be distributed to other NMR labs. We envisage that in future linking of NOMAD instances together could possibly create very useful Open Access NMR Data Repository.
Development of prototype MOF/polymer coatings for medical applications
On any given day, approximately one in 25 US patients has at least one infection contracted during the course of their hospital care, demonstrating the need for improved infection control in healthcare facilities. The majority of these infections result from the handling and insertion of some form of device into the body, such as a central line into the bloodstream or urinary catheterisation. Research has shown that when specific preventative steps are taken, the rates of infection can be drastically decreased by up to 70%.
The biologically active gas nitric oxide (NO) could help in the fight against such infections. NO plays an important signalling role in numerous pathways within the body triggering vasodilatory (increasing blood flow), anti-thrombotic and angiogenetic (new blood vessel growth) properties as well as being a broad spectrum antimicrobial agent. However, to date, there are no commercially available products that allow the controlled delivery of NO – primarily due to its physical nature (i.e. a gas) and the requirement to deliver specific doses.
With this in mind, we are developing porous powders called metal organic framework (MOFs) that are able to store and controllably release NO. These powders can be incorporated into coatings on medical devices and can be designed to deliver NO at the correct doses and over appropriate time scales to prevent infection. Furthermore, by using antimicrobial metal ions in the MOF frameworks additional efficacy can be imparted. The technology, which has the potential to reduce healthcare associated infections and procedural complications, is the basis for a new spin-out company called MOFgen Ltd.
Novel drug tools for neglected diseases: Development of tools for target identification of nitrofuran-carboxyamides with potent trypanocidal activity
Parasitic protozoan disease, such as African sleeping sickness, Chagas disease and leishmaniasis are some of the most neglected diseases in the world. The WHO have highlighted these diseases as a priority as a third of the world’s population are at risk; it effects millions of people and represents a huge percentage of the world’s disease burden. Current drug treatments are woefully inadequate, as many suffer from problems of toxicity, difficulty of administration in the field, cost and rapidly emerging parasite resistance. Therefore, there is an urgent need to identify novel therapeutic targets and to develop effective lead compounds that are safe, cheap and easy to administer against these protozoan diseases.
We have been optimising novel analogues of nifurtimox (a current front-line drug against some of these diseases), but with activity ~1000-fold more potent and without the side effects that nifurtimox has. Importantly, these novel analogues are relatively easy to synthesise and therefore cheap, and they are targeting a different, but still an essential biochemical process to those targeted by nifurtimox.
We are developing and utilising novel tools that allow us to elucidate the mode of action of our novel drugs, by identifying the protein target(s) they interact with and their subsequent metabolism. Collectively, these findings will have important implications for the future therapeutic treatment of African sleeping sickness, Chagas disease and possibly leishmaniasis. Our research involves utilising a multi-disciplinary approach spanning chemistry, biochemistry and molecular parasitology. The chemical technologies developed will be broadly applicable to protein target identification in general with the potential to simplify this challenging facet in the drug discovery process.
The figure at the top shows a stained trypanosome parasite and a chemical structure of one of the simplest chemical probes we are using to elucidate how our new compounds work within the parasite.
How can robot behaviour be safely unscripted?
As robots move into more uncontrolled environments, safe motion requires flexibility to deal with the unexpected. In this research, scripted behaviours and their limitations in robots are compared with unscripted designs. The NAO humanoid robot for instance has a good example of a scripted language and a wide ranging physical capability for such comparison. The aim is to investigate ways in which moves can be made towards motion on an unscripted basis with less limitations which is also safe.
Single pixel compressive imaging
An image is worth a thousand words. This statement holds not only true in every day life but even more so in science. In a broader sense any position dependent measure can be understood as an imaging technique. One of the major challenges in imaging is correcting for aberrations, improving speed of imaging and reducing photo toxicity. The proof of concept that this project is developing aims to overcome, to some extent, these challenges. To do this we use structured illuminations and compressive sensing techniques. This approach aims at developing a toolbox (software and hardware) that can be used in medical and bio-photonics imaging context.
Optical Eigenmodes: http://www.eigenoptics.net/