Interface reaction of the SnS/BaSi2 heterojunction fabricated for solar cell applications

The heterojunction of p-type SnS and n-type BaSi2 is an attractive architecture of thin-film solar cells because of suitable optical properties and the abundance of constituent elements. In this study, we investigated the interface reaction between SnS and BaSi2 deposited at 31-350 degrees C by thermal evaporation. SnS forms at all temperatures while 350 degrees C is too low to form BaSi2, as indicated by X-ray diffraction. Auger depth analysis reveals an interface reaction at 350 degrees C with chemical shifts of all relevant elements. A possible reaction, which yields BaS, Si, and Sn, is consistently proposed. The interface reaction is suppressed by deposition at low temperatures of 31-250 degrees C owing to the Si layer formed just below the SnS layer. Postannealing at 400 degrees C yields a SnS/BaSi2 heterojunction with suppressed interface reaction. Sn segregation on the surface is evidenced by Auger microanalysis. The fabricated solar cells show slight power generation, which could be improved by suppressing the interface re-action.