Visible to near-infrared light harvesting in Ag ₂S nanoparticles/ZnO nanowire array photoanodes

Pronounced absorption in the visible-NIR range of 400-1300 nm is demonstrated in the Ag ₂S nanoparticles (NPs)/ZnO nanowire (NW) array. ZnO NW arrays are grown on indium tin oxide substrates using chemical bath deposition. The Ag ₂S NPs are sequentially formed on the ZnO NWs through sonochemical synthesis. Structural characterizations indicate the slight deconstruction of surface of ZnO NWs during Ag ₂S NPs formation. By employing polysulfide electrolyte, short-circuit current (J _sc), open-circuit voltage and therefore the efficiency of the Ag ₂S NP-sensitized ZnO NW solar cell are improved with increasing the initial sulfur concentration in the sulfur-polysulfide electrolyte. The Ag ₂S NP-sensitized ZnO NW solar cell shows a conversion efficiency of 0.49% with a superior J _sc of ∼13.7 mA cm ^-2 under AM 1.5 illumination at 100 mW cm ^-2. Incident photon conversion efficiency measurements reveal that Ag ₂S NPs contribute to 33.4% and 65.2% of J _sc in the wavelength ranges of 400-700 nm and 700-1300 nm, respectively.