Perovskite Heterostructures by Vapour Deposition

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics


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.

Planned Impact

This project will advance methods for the vapour deposition of perovskite semiconductors, and realise efficient, cost-effective, large area, all-perovskite multilayer photovoltaic (PV) devices. It is our vision and motivation that over a 10 to 20 year time scale, the cost of electricity from PV will drop to less than a quarter the cost of producing electricity from coal. This has the potential to, and in our view will, deliver a zero-carbon future within a 30 year timeframe.
There is overwhelming evidence that our increasing consumption of fossil fuels and the associated emission of carbon dioxide is leading to climate change. This has brought new urgency to the development of clean, renewable sources of energy, and to reduction of our energy consumption by developing new low energy consumption devices to satisfy the growing demand. Photovoltaic devices that harvest the energy provided by the sun have great potential to contribute to the solution, but uptake of photovoltaic energy generation has been weakened by the cost of devices based on current technology. Although silicon PV continues to steadily drop in price, the key to creating a step reducing cost is the development of new photovoltaic materials either offering a step increase in efficiency or allowing easy, large-scale processing from solution or low-temperature evaporation, neither of which require costly purification and high-energy, slow deposition processes. Very high efficiency solar cells have been realised in group-III-V materials using tandem and multi-junction architectures, but at present the production costs of these devices are high, making them uneconomic for large-area deployment. The route we are undertaking here is to exploit recent advances made in solution-processed metal halide perovskite materials by transferring them to the industrially relevant technique of vapour deposition. The vapour deposition technique will not only allow the cost-effective production of highly uniform large area solar cells with high yield, but will also enable a step improvement in device efficiency by creating tandem and multi-junction solar cells.
The global PV market is currently close to $100bn pa. Although 90% of the market is presently met by c-Si and only 10% by thin-film, low cost thin-film approaches still look set to offer the lowest prices on a 10 to 50 year timescale, allowing solar energy to compete favourably on price with fossil fuels. Establishing all-perovskite tandem solar cells will boost the efficiency, while the vapour deposition method will enable large devices and close to 100% device yields, together delivering a premium product for the entire PV market. This could then access the majority of a $100bn market, and then further accelerate the growth of the PV market as a whole.
The vapour-deposition technology developed in the project will create uniform, large area solar cells with high efficiencies and device yields. This technology is compatible with infrastructure used in industry for large-area thin-film deposition, and thus the outcomes of the project could be immediately transferred to the UK manufacturing industry. This has the potential to put UK at the forefront of the expanding "green energy" economy both in terms of solar cell manufacturing and the growing business of large area terrestrial solar power generation. Beyond commercial, economic, environmental and societal impact, the activities within this project will aid in the training and education of both scientists and the general public. The training of PDRAs and PhD students in this industrially relevant area will create an employment pool for jobs in research, R&D, energy sectors and other economic areas, and carry the knowledge and skills they acquire into those fields. The project's outreach activities will engage and inform the public and inspire young minds to become our future generation technologists and leaders.


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