There is currently a pressing global need to reduce emissions of carbon dioxide, and at the same time satisfy the world's growing desire for cheap electricity. Solar cells, which directly convert the Sun's radiation into electricity, offer a realistic method of generating electricity sustainably, on a large scale and at costs similar to and even lower than more polluting conventional forms of power generation (coal, gas, nuclear). Over the past few years a new class of solar cells based on metal-halide perovskite semiconductors has emerged. Power conversion efficiencies for these materials have increased at an unprecedented rate for a new photovoltaics material and now exceed 20%. An intense worldwide research effort into these materials is now underway; however nearly all research is focussed on solution processed perovskites, and most highly efficient solar cells are small area devices not suited to large area deployment. In this project we will build on our early lead in the area of vapour deposited perovskites to develop highly efficient large area perovskite solar cells. Our evaporation technique offers superior film uniformity over large areas and is highly reproducible as compared with more common solution processing methods. Using the vapour deposition route we will develop all-perovskite tandem and multi-junction solar cells to further improve the efficiency for these remarkable devices. We utilise the recently funded EPSRC "National thin-film cluster facility for advanced functional materials" to adapt our advances in perovskite materials and device technologies to current industrial thin-film production methods.