Ag(8)SnS(6): a new IR solar absorber material with a near optimal bandgap

We report the synthesis and photovoltaic properties of a new ternary solar absorber – Ag(8)SnS(6) nanocrystals prepared by successive ionic layer adsorption reaction (SILAR) technique. The synthesized Ag(8)SnS(6) nanocrystals have a bandgap E(g) of 1.24–1.41 eV as revealed from UV-Vis and external quantum efficiency (EQE) measurements. Its photovoltaic properties were characterized by assembling a liquid-junction Ag(8)SnS(6) sensitized solar cell for the first time. The best cell yielded a J(sc) of 9.29 mA cm(−2), a V(oc) of 0.23 V, an FF of 31.3% and a power conversion efficiency (PCE) of 0.64% under 100% incident light illumination using polysulfide electrolyte and Au counter electrode. The efficiency improved to 1.43% at a reduced light intensity of 10% sun. When the polysulfide was replaced by a cobalt electrolyte with a lower redox level, the V(oc) increased to 0.54 V and PCE increased to 2.29% under 0.1 sun, a respectable efficiency for a new solar material. The EQE spectrum covers the spectral range of 300–1000 nm with a maximum EQE of 77% at λ = 600 nm. The near optimal E(g) and the respectable photovoltaic performance suggest that Ag(8)SnS(6) nanocrystals have potential to be an efficient IR solar absorber.