UNIST team demonstrates new lead-free perovskite

A team of researchers from UNIST in South Korea has identified a tin-based perovskite which could open new possibilities for the application of lead-free perovskites in solar cells. The cesium-tin based double perovskite material, Cs₂SnI₆, had previously been identified as promising for use in solar cells, however little research into the perovskite's surface properties had been carried out.

The team created a three-electrode system allowing them to confirm that charge transfer occurred through the surface state of the material; and used this knowledge to engineer a Cs₂SnI₆ based organic dye sensitized solar cell.

'Due to a high volume of electrical charges in organic dyes that show high connectivity with the surface state of Cs₂SnI₆, more electric current were generated,' says Byung-Man Kim in the Department of Chemistry at UNIST, a lead author of this study. 'Consequently, Cs₂SnI₆ shows efficient charge transfer with a thermodynamically favorable charge acceptor level, achieving a 79% enhancement in the photocurrent density compared with that of a conventional liquid electrolyte.'

This study was said to be one of the first into the charge transfer mechanism of Cs₂SnI₆, and its results suggest that the surface state is a key issue to be considered in the design of such devices.