In view of the worldwide energy challenge in the 21(st) century, the technology of semiconductor-based photoelectrochemical (PEC) water splitting has received considerable attention as an alternative approach for solar energy harvesting and storage. Two-dimensional (2D) structures such as nanosheets have the potential to tap the solar energy by unlocking the functional properties at the nanoscale. Tin(ii) sulfide is a fascinating solar energy material due to its anisotropic material properties. In this manuscript, we report on exploiting the 2D structure modulated optical properties of nanocrystalline SnS thin film synthesized by chemical spray pyrolysis using ambient transport in the harvesting of solar energy. We obtained the nanostructured SnS with well-preserved dimensions and morphologies with one step processing. The work demonstrates that the intrinsically ordered SnS nanostructure on FTO coated glass can tap the incident radiation in an efficient manner. The structure-property relationship to explain the photo-response in nanocrystalline-SnS is verified experimentally and theoretically. The novel design scheme for antireflection coating along with the anisotropic properties of SnS is conceived for realizing a PEC cell. The developed PEC cell consists of a SnS photoanode which shows considerably high photocurrent density of 7 mA cm(-2) with aqueous media under AM 1.5G, 100 mW cm(-2) exposure with notably stable operation. Electrochemical impedance spectroscopy revealed that a non-ideal capacitive behavior as well as drift assisted transport across the solid-state interface is responsible for such a high photo-current density in the nanocrystalline-SnS photoanode.
The
coexistence of secondary phases in the quaternary compound
kesterite Cu2ZnSnS4 (CZTS), a promising photovoltaic
absorber, is a major problem while synthesizing under Zn or Cu rich
conditions. A large variety of secondary phases, such as CuS, Cu1.8S, Cu2S, Cu2SnS3, and ZnS
exist on the surface unless they are not removed by dedicated surface
treatment before the annealing step. Under a carefully chosen concentrations
of the starting precursors (usually, Zn-poor and Sn-rich) for spray
pyrolyzed CZTS, the fraction of ZnS is minimized. However, under such
growth conditions, binary Cu-sulfides become dominant. In this work,
a selective noncyanide based chemical etching procedure is demonstrated
prior to the deposition of the buffer layer. The absorber surface
was treated with hydrogen peroxide that is known to remove Cu1.8S, Cu2S, and allied secondary phases to a large
extent as compared to conventional KCN based techniques. By this treatment,
the optical band gap is changed from 1.8 eV to most suitable 1.5 eV,
which ensures improved photon absorption.
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