(Invited) Copper Kesterite Photocathode for Photoelectrochemical Water Splitting

Abstract

Copper kesterite, Cu2Zn(S,Se)4, with tunable bandgap between 1.1 – 1.7eV, is one of the most promising candidates for emerging thin film solar cell. It also has many suitable attributes of a photocathode for photoelectrochemical solar water splitting such as good absorption coefficient and conduction band maximum > H2O/H2 reduction potential. However the photocurrent and onset potential are relatively poorer due to tendency of forming deep defects associated with Cu, Zn, Sn antisites and interfacial defects. In this talk, I will present our group’s efforts in eliminating these defects by cation substitution. We found that partially substituting Zn with Cd improved its carrier mobility and lifetime and resulted in 4x enhancement of photocurrent. Ag partial substitution of Cu resulted in reduced defects at the CZTS/CdS interface and led to better onset potential. Finally, we show the use of transparent conducting oxide which not only improves the electron transport to the electrolyte, but also improves the long term stability of the photocathode.