An Iranian-Italian research group has simulated a double-junction tandem solar cell based on a perovskite and tin sulfide. They said that it can reach an efficiency rating of between 22.9% and 28.92%.

Tin(II) sulfide (SnS) has emerged in recent years as a promising semiconductor material for solar cells. It is abundant in nature, non-toxic, and can be supplied at a low cost. Furthermore, it has a near-optimal direct bandgap of about 1.3 eV, a high level of environmental and chemical stability, and a high absorbance coefficient.

With this in mind, a group of researchers from Shiraz University in Iran and the University of Rome Tor Vergata has designed a double-junction tandem solar cell based on a perovskite top-cell and an SnS sub-cell.

“SnS solar cells are a potential alternative to current low-bandgap subcells used in combination with perovskite solar cells to produce highly efficient tandems,” researcher Farshad Jafarsadeh told pv magazine.

In the proposed cell configuration, SnS is used for the buffer layer in the narrow-bandgap cell.

“We investigated the variation of thicknesses, carrier concentrations, and defect densities of the SnS and n-SnS layer on the PV parameters,” the scientists said.

The noted that the device was developed through a numerical simulation performed via SCAPS-1D, which is a simulation tool for thin-film solar cells developed by the University of Ghent in Belgium. The top cell and the sub-device were investigated separately and then connected in series to simulate a tandem cell.

“Based on numerical simulations, SnS homojunction solar cells operate best with a p-type layer of 2 µm thick and the n-type layer of 0.4 µm thick,” the academics explained. “Simulations proved that a 22.9% efficient SnS solar cell is possible.”

According to their estimations, such kinds of cells have the potential to reach a power conversion efficiency of up to 28.92%.

“The downside is that up to now fabricated SnS solar cells gained lower efficiency than the simulated ones which means there should be more research effort in the future in this area,” said Jafarsadeh.

They described the cell design in “Design and optimization of highly efficient perovskite/homojunction SnS tandem solar cells using SCAPS-1D,” which was recently published in Solar Energy.