Electrochemically Deposited Sb and In Doped Tin Sulfide (SnS) Photoelectrodes.

Semiconducting tin sulfide (SnS) was deposited electrochem. from electrolytes contg. Sn and S precursors and conditions optimized to maximize its performance as a photoelectrode. Films composed of primarily orthorhombic SnS were electrodeposited on titanium substrates from electrolyte contg. 20 mM SnSO4 and 100 mM Na2S2O3 at pH 2.5. For deposition a cathodic pulse of -1.25 V vs Ag/AgCl was applied for 2.75 s followed by a 0.25 s pulse of +0.25 V vs Ag/AgCl repeated for 30-45 min. The films were annealed in argon at 300 °C for 3 h. The addn. of SbCl3 (<5%) to the electrolyte gave rise to doping of the SnS film with Sb which resulted in an increase in the photocurrent as well as a switch from p- to n-type semiconducting behavior in an acidified Na2S2O3 electrolyte. Incorporation of p-type In into the films from addn. of In(NO3)3 had a smaller effect on the measured photocurrent, and at higher precursor concn. (>5%) the dopants resulted in the formation of secondary phases of Sb and In oxides with redn. in the measured photocurrent. This doped SnS material could potentially be used in systems for the photoelectrochem. prodn. of hydrogen and oxidn. of org. wastewater. D. functional theory calcns. supported the exptl. obsd. cond. increase for photoelectrons as an Sb dopant induced curvature of the valence band. These calcns. also provided an explanation to the previous exptl. work where Sb doping was used to decrease the resistivity of SnS films. The combination of an automated electrodeposition of an earth abundant metal sulfide with the theor. calcns. to guide the synthesis is an exemplar of how to improve the efficiency of SnS-based solar energy conversion materials. [on SciFinder(R)]