Non-stoichiometric Cu–In–S@ZnS nanoparticles produced in aqueous solutions as light harvesters for liquid-junction photoelectrochemical solar cells

Alexandra Raevskaya,Dietrich R T Zahn,Andriy Kozytskiy,Volodymyr Dzhagan,Oksana Rosovik,Oleksandr Stroyuk

doi:10.1039/c6ra18313a

Abstract

A direct “green” aqueous synthesis of mercapto acetate-stabilized copper indium sulfide (CIS) nanoparticles (NPs) and core/shell CIS@ZnS NPs of a varied composition under ambient conditions and a temperature lower than 100 °C is reported.

Highlights

The nanoparticles (NPs) of cadmium and lead chalcogenide semiconductors combine strong absorbance in the UV/visible spectral range, prominent luminescent and/or photochemical properties, and pronounced size dependences of the photophysical characteristics due to con nement effects
The reported conduction band (CB) edge of copper indium sulfide (CIS) NPs is around À0.5 V (vs. normal hydrogen electrode (NHE)) for the stoichiometric CuInS2 and shi s to more negative values for the NPs with a lower molar Cu : In ratio.[12,13]
The experiments discussed further in details showed that the highest photoelectrochemical activity is observed for the CIS NPs with a molar Cu : In : S ratio of 1 : 5 : 10

Summary

Introduction

The nanoparticles (NPs) of cadmium and lead chalcogenide semiconductors combine strong absorbance in the UV/visible spectral range, prominent luminescent and/or photochemical properties, and pronounced size dependences of the photophysical characteristics due to con nement effects. The chalcopyrite CIS NPs can be prepared with large variations in stoichiometry while preserving the chalcopyrite structure with no additional binary phases.[5,6,7,8] Both stoichiometric CuInS2 and non-stoichiometric Cu–In–S NPs reveal broad absorption bands extending to around 800 nm (for bulk CuInS2 the bandgap Eg is 1.5 eV) and quite a high absorption coefficients exceeding 105 cmÀ1.6,7 At the same time, the CIS NPs are reasonably stable both in the dark and under photoexcitation.[5,6,7] A combination of these features makes CIS NPs a good candidate as a visible light harvester both for solid-state photovoltaic solar cells and liquid-junction photoelectrochemical solar cells.[5,6,7,8,9,10,11] In the latter systems, the CIS NPs act as a spectral sensitizer that absorbs through the entire visible light range. Paper and injects electrons into a wide-band-gap metal oxide component of the photoanodes.[6,7,9,10,11] The reported conduction band (CB) edge of CIS NPs is around À0.5 V (vs normal hydrogen electrode (NHE)) for the stoichiometric CuInS2 The CIS NPs can be used as a charge transfer layer in the solid-state solar cells[15] and as a counter-electrode component for the dye-sensitized solar cells[12] as well as photocatalysts of a number of redox processes including dyes degradation[16] and water splitting.[11,17]

Methods

Results

Conclusion