Photoelectrochemical performances of kesterite Ag2ZnSnSe4 photoelectrodes in the salt-water and water solutions

In this study, we prepare quaternary silver-zinc-tin-selenide samples on various substrates using the selenization of thermally evaporated silver-zinc-tin metal precursors. The [Zn]/[Sn] molar ratio in metal precursors is verified to study its influence on the structural, optical and photoelectrochemical properties of the Ag-Zn-Sn-Se samples in various electrolytes. After various selenization tests, a selenization process with the temperature of 410 degrees C and time of 90 min is employed for the preparation of quaternary Ag-Zn-Sn-Se samples. X-ray diffraction patterns and Raman spectra of samples show that the crystal phases of samples change from the cubic AgSnSe2/kesterite Ag2ZnSnSe4 mixing phases, the kesterite Ag2ZnSnSe4 phase to the kesterite Ag2ZnSnSe4/cubic ZnSe mixing phases with an increase in the [Zny[Sn] molar ratio in the metal precursors. Direct energy band gaps of samples locate in the range of 1.30-1.34 eV. Carrier concentration and mobility of samples are in the ranges of 8.99 x 10(15)-5.97 x 10(15) cm(-3) and 7.72-76.08 cm(2)/V s, respectively. The sample with the [Zn][Sn] molar ratio of 1.42 has the maximum photo-enhancement current density of 5.69 and 11.12 mA/cm(2) at an applied bias of +1.0 V vs. an Ag/AgCI electrode in the 0.5 M K2SO4 and 1 M NaCI aqueous solution, respectively. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.