British researchers claim tin-based PV perovskites offer cleaner, cheaper lead alternative

Researchers at the University of Warwick in the U.K. believe that they can produce an environmentally friendly perovskite solar cell in which lead is substituted for tin with no impact on efficiency or performance.

In a paper published in Nature Energy, the group claim that tin is also a cheaper substitute, and by basing perovskite cells on such a material could expedite the technology’s adoption across a number of solar-based applications.

According to professor Richard Walton and Ross Hatton, who led the Warwick team, tin-based perovskites are much more stable than previously thought, and also render solar power cheaper, safer and – potentially – more commercially attractive. "The device structure can be greatly simplified without compromising performance, which leads to the important advantage of reduced fabrication cost," read the report in Nature Energy.

Tin’s efficacy in perovskite development has been underexplored for many years, largely due to an erroneous belief that the material of tin perovskite could be too susceptible to oxidization, the low energy of defect formation and an added difficulty in forming pinhole-free films.

According to the researchers, perovskite PV devices that do not require a hole-selective interfacial layer are around 10 times more efficient than devices with the same architecture based on methylammonium lead iodide perovskite. The highest efficiency to date for a CsSnl3 PV cell is 3.56%.

"We have shown that the improved performance and tolerance to pinholes in the perovskite film stems from n-doping of the fullerene electron-transport layer by SnCl2, and that the stability of unencapsulated CsSnI3 is improved by at least an order of magnitude as compared to lead-based PPV," said the paper.

"Our findings justify an intensive research effort into tin perovskite PV, focused on improving ? to a level comparable to that of lead perovskite PVs."

Perovskite’s promise in PV has been undermined by its inherent instability when exposed to real world conditions. The use of lead in creating perovskite cells has helped to push the industry forward in terms of durability, but has raised question marks over cost and toxicity within many research fields.