Perovskite semiconductors are a new class of semiconductor that can be used as the active layer in photovoltaic (solar cell) devices, producing low-carbon electricity directly from sunlight. The best perovskite solar cells can now convert sunlight to electrical energy with an efficiency of over 22%, with such devices being produced using solution based techniques. Here, a perovskite 'precursor' solution can be spread over a surface which then forms the perovskite semiconductor material. This process is expected to allow perovskites to be 'printed' onto surfaces, allowing solar cells to be produced at very low cost.

In this project, we will focus on the use of spray-coating to deposit perovskite solar cells. Spray-coating is routinely used to coat paints and pigments in many manufacturing processes, and critically is not restricted to coating 'flat' surfaces, but can cover curved surfaces - for example the curved roof of an automobile. We will take full advantage of this, and will make the first detailed study of the use of spray-coating to coat perovskite solar cells over non-planar surfaces, e.g. over cylinders or aerofoil-shapes (similar to the shape of an aeroplane-wing).

We believe that the results of this work will form the basis of a series of new technologies. A particular focus of our work will be to use spray-based techniques to coat perovskite PV over carbon-fibre composite materials. Carbon-fibre is already widely used in industry as a high-performance, light-weight engineering material - e.g. forming the body of sports-cars, the hulls of yachts and in other demanding applications. By coating the surface of carbon-fibre with a solar-cell, we will be able to create a new class of super-strong, lightweight materials that are able to generate electricity from sunlight at low cost.

We believe such materials will be of particular importance in generating power for mobile applications, and will have identified a range of applications in the aerospace and automotive sectors. To realize such a task we have assembled a team of researchers having world-leading expertise in the development of spray and deposition techniques to fabricate perovskite solar cells, together with researchers expert in the processing and testing of carbon-fibre composite materials. A key part of the project will be to understand the interactions between the different materials that we will deposit and the carbon fibre surface. We will make a full characterization of the mechanical properties of the solar-cells we develop, and will explore techniques to 'encapsulate' such devices to maximise their operational lifetime.

Potential Impact:
The UK excels in the high volume manufacture of composite materials, having a range of applications in specialist vehicles, marine, the rail industry and in renewable technologies. The proposed research will directly benefit UK companies involved in composites manufacturing and supply, and companies interested in the uses of such materials. The research is also set against the background of the UK solar industry that has undergone very rapid growth in the last 5 years. Here, a number of large UK companies are directly involved in PV manufacturing including the glass manufacturer Pilkington. The UK also has a nascent perovskite PV industry (Oxford PV, Big Solar Ltd).

We expect the combination of perovskite PV with CF composites that we will develop will create an exciting class of super-strong, lightweight materials that are able to function as structural materials that are able to generate electricity. There is range of emerging applications for PV enabled composite materials that will be stimulated by the demonstration of the enabling technologies we propose. These include PV cladding for buildings, trickle-charge for automobiles and power for safety-helmets, and solar-power for autonomous aerial vehicles (AUVs). Here AUVs are currently being developed to provide internet access to people in unconnected regions such as sub-Saharan Africa. Solar AUVs are also expected to have significant applications in environmental monitoring and disaster relief etc. By necessity such solar AUVs need a large wingspan to collect sufficient power to maintain their flight and thus the scalable spray-coating technology we outline is well suited for this task.

We propose a range of activities to gain Impact for our research:

(1) We will work with the Advanced Manufacturing Research Centre (AMRC) Design & Prototyping Group to develop a fixed-wing, radio-controlled model aircraft that - using the spray-cast carbon-fibre devices - will be capable of either partial (i.e. battery augmented) or full solar-powered flight. This demonstrator will be used to develop new commercial partnerships by hosting a small stand at the Advanced Engineering Show at the NEC in Birmingham.

(2) We will also work with two companies (Big Solar Ltd and Greatcell Solar Ltd) who are interested in the deposition techniques that we will develop in the project. In particular, the deposition of perovskite films over large areas by spray-coating, the development of charge-transport materials compatible with heat- and chemically-sensitive substrates, and the necessity to develop low-cost encapsulation is of critical importance to companies looking to commercialize perovskite solar cell technologies. One of our partner companies will fund a substantial level of research time to cover the transfer of knowledge between this project and the company, allowing our basic science research to find near-term applications in commercial products.

(3) We will assemble a network of interested parties having a background in PV device engineering and in the use and manufacture of carbon-fibre composites during the course of the project. This includes the company Prismatic Ltd who have a direct interest in developing AUVs as low-cost, low-altitude satellites. We will write a series of articles about our project for different trade magazines. This will help us identify technology-partners and end-users, an activity that will be important for further development of the technology beyond the lifetime of the project.

Finally, this project will have a significant impact on the careers of the researchers we will employ. We will employ 3 PDRAs and two PhD students who will address the development of manufacture techniques, testing, metrology and the evaluation of new types of PV devices. We are confident that the experience gained in these areas will meet UK industry's growing demands for highly-trained researchers in advanced manufacture.