As the world population grows, the total energy demanded increases, despite the limited reserves of fossil fuels. Energy sources based on new technologies, such as the photovoltaic cells are a sustainable and environmentally clean option. Most of the photovoltaic cells produced are based in silicon, a material that even though presents several advantages for the industry, fails to absorb the energy of the entire solar spectrum. One interesting option to increase device efficiencies is to produce stacks of complementing cells, known as tandem cells, thus taking advantage of the full solar spectrum. Tandems of Si and novel perovskite cells are a feasible alternative and can be synthesized from cheap and abundant materials.
On the other hand, the main requirements in industry are low cost, high throughput and process reliability. Thus, production techniques and materials should be selected bearing in mind a compromise between cost reduction, acceptable efficiencies and process yield.
The aim of the project PerSiSTanCe (Low-cost and Large-Area Perovskite-Silicon Solar Tandem Cells) was producing large area and low cost perovskite tandem solar cells with industry friendly methods and materials, selected bearing in mind the most appropriate for their implementation in tandem Si/perovskite cells. The priority was the substitution of layers whose use would involve scarce/strategic materials or difficult and/or expensive processes. The result should be more robust and reliable processes and devices, contributing to reducing the gap between laboratory devices and the future mass production tandem cells.
Big steps have been given in this direction, all the components of the standard cell have been subject of analysis and optimization, resulting in a control standard device of around 21% efficiency. On the other hand, planar and inverted devices, the most favourable architecture for tandem devices was developed for the first time at the Adolphe Merkle Institute, achieving an efficiency of 17.4% thanks to a low cost solution processed nickel oxide hole transport layer, improved passivation interlayers and an optimized perovskite absorber. This result paves the way towards the in-house production of semi-transparent and perovskite-in-perovskite tandem devices.
