Most solar cells currently on the market are made of silicon, however they are expensive to make and require a lot of very pure silicon to manufacture. They are also quite thick and heavy, which limits their applications.
The lightweight perovskite solar cells are cheaper to make, thinner and can be easily printed onto surfaces. They also work in low light conditions and can produce a higher voltage than silicon cells which is vital for hydrogen production. The downside is they are unstable in water which presents a huge obstacle in their development and also limits their use for the direct generation of clean hydrogen fuels.
The team from the University of Bath’s Centre for Sustainable Chemical Technologies, has solved this problem by using a waterproof coating from graphite.
“Currently hydrogen fuel is made by burning methane, which is neither clean nor sustainable," said Isabella Poli, Marie Curie FIRE Fellow and PhD student from the Centre for Sustainable Chemical Technologies. “But we hope that in the future we can create clean hydrogen and oxygen fuels from solar energy using perovskite cells.”
They tested the waterproofing by submerging the coated perovskite cells in water and using the harvested solar energy to split water into hydrogen and oxygen. The coated cells worked underwater for 30 hours – ten hours longer than the previous record. Previously, alloys containing indium were used to protect the solar cells for water splitting, however indium is a rare metal and is therefore expensive and the mining process to obtain it is not sustainable. The Bath team instead used commercially available graphite, which is very cheap and much more sustainable than indium.
“Perovskite solar cell technology could make solar energy much more affordable for people and allow solar cells to be printed onto roof tiles. However at the moment they are really unstable in water - solar cells are not much use if they dissolve in the rain," said Dr Petra Cameron, Senior Lecturer